Proposed diagnostic criteria for the diagnosis of hypophosphatasia in children and adolescents: results from the HPP International Working Group.

Hypophosphatasia (HPP) is a rare inborn error of metabolism that presents variably in both age of onset and severity. HPP is caused by pathogenic variants in the ALPL gene, resulting in low activity of tissue nonspecific alkaline phosphatase (TNSALP). Patients with HPP tend have a similar pattern of elevation of natural substrates that can be used to aid in diagnosis. No formal diagnostic guidelines currently exist for the diagnosis of this condition in children, adolescents, or adults. The International HPP Working Group is a comprised of a multidisciplinary team of experts from Europe and North America who have expertise in the diagnosis and management of patients with HPP. This group reviewed 93 papers through a Medline, Medline In-Process, and Embase search for the terms "HPP" and "hypophosphatasia" between 2005 and 2020 and that explicitly address either the diagnosis of HPP in children, clinical manifestations of HPP in children, or both. Two reviewers independently evaluated each full-text publication for eligibility and studies were included if they were narrative reviews or case series/reports that concerned diagnosis of pediatric HPP or included clinical aspects of patients diagnosed with HPP. This review focused on 15 initial clinical manifestations that were selected by a group of clinical experts.The highest agreement in included literature was for pathogenic or likely pathogenic ALPL variant, elevation of natural substrates, and early loss of primary teeth. The highest prevalence was similar, including these same three parameters and including decreased bone mineral density. Additional parameters had less agreement and were less prevalent. These were organized into three major and six minor criteria, with diagnosis of HPP being made when two major or one major and two minor criteria are present.

The challenge of hypophosphatasia diagnosis in adults: results from the HPP International Working Group Literature Surveillance.

Hypophosphatasia (HPP) is an inborn error of metabolism caused by reduced or absent activity of the tissue non-specific alkaline phosphatase (TNSALP) enzyme, resulting from pathogenic variants in the ALPL gene. Clinical presentation of HPP is highly variable, including lethal and severe forms in neonates and infants, a benign perinatal form, mild forms manifesting in adulthood, and odonto-HPP. Diagnosis of HPP remains a challenge in adults, as signs and symptoms may be mild and non-specific. Disease presentation varies widely; there are no universal signs or symptoms, and the disease often remains underdiagnosed or misdiagnosed, particularly by clinicians who are not familiar with this rare disorder. The absence of diagnosis or a delayed diagnosis may prevent optimal management for patients with this condition. Formal guidelines for the diagnosis of adults with HPP do not exist, complicating efforts for consistent diagnosis. To address this issue, the HPP International Working Group selected 119 papers that explicitly address the diagnosis of HPP in adults through a Medline, Medline In-Process, and Embase search for the terms "hypophosphatasia" and "HPP," and evaluated the pooled prevalence of 17 diagnostic characteristics, initially selected by a group of HPP clinical experts, in eligible studies and in patients included in these studies. Six diagnostic findings showed a pooled prevalence value over 50% and were considered for inclusion as major diagnostic criteria. Based on these results and according to discussion and consideration among members of the Working Group, we finally defined four major diagnostic criteria and five minor diagnostic criteria for HPP in adults. Authors suggested the integrated use of the identified major and minor diagnostic criteria, which either includes two major criteria, or one major criterion and two minor criteria, for the diagnosis of HPP in adults.

Hypophosphatasia diagnosis: current state of the art and proposed diagnostic criteria for children and adults.

BACKGROUND: This manuscript provides a summary of the current evidence to support the criteria for diagnosing a child or adult with hypophosphatasia (HPP). The diagnosis of HPP is made on the basis of integrating clinical features, laboratory profile, radiographic features of the condition, and DNA analysis identifying the presence of a pathogenic variant of the tissue nonspecific alkaline phosphatase gene (ALPL). Often, the diagnosis of HPP is significantly delayed in both adults and children, and updated diagnostic criteria are required to keep pace with our evolving understanding regarding the relationship between ALPL genotype and associated HPP clinical features. METHODS: An International Working Group (IWG) on HPP was formed, comprised of a multidisciplinary team of experts from Europe and North America with expertise in the diagnosis and management of patients with HPP. Methodologists (Romina Brignardello-Petersen and Gordon Guyatt) and their team supported the IWG and conducted systematic reviews following the GRADE methodology, and this provided the basis for the recommendations. RESULTS: The IWG completed systematic reviews of the literature, including case reports and expert opinion papers describing the phenotype of patients with HPP. The published data are largely retrospective and include a relatively small number of patients with this rare condition. It is anticipated that further knowledge will lead to improvement in the quality of genotype-phenotype reporting in this condition. CONCLUSION: Following consensus meetings, agreement was reached regarding the major and minor criteria that can assist in establishing a clinical diagnosis of HPP in adults and children.

New insights into the landscape of ALPL gene variants in patients with hypophosphatasia from the Global HPP Registry.

Hypophosphatasia (HPP) is a rare, inherited metabolic disease characterized by low tissue-nonspecific alkaline phosphatase activity due to ALPL gene variants. We describe ALPL variants from the observational, prospective, multinational Global HPP Registry. Inclusion in the analysis required a diagnosis of HPP, low serum ALP activity, and ≥1 ALPL variant. Of 1176 patients enrolled as of September 2022, 814 met inclusion criteria in Europe (48.9%), North America (36.7%), Japan (10.2%), Australia (2.6%), and elsewhere (1.6%). Most patients (74.7%) had 1 ALPL variant; 25.3% had ≥2 variants. Nearly all patients (95.6%) had known disease-causing variants; 4.4% had variants of uncertain significance. Disease-causing variants were predominantly missense (770/1556 alleles). The most common variants were c.571G>A (102/1628 alleles), c.1250A>G (66/1628 alleles), and c.1559del (61/1628 alleles). Variant profiles were generally consistent, except in Japan, where a higher proportion of patients (68.7%) had ≥2 ALPL variants, likely because more had disease onset before age 6 months (53.0% vs. 10.1%-23.1% elsewhere). Frameshift mutations (61/164 alleles) and inframe deletions (7/164 alleles) were more common in Japan. Twenty-three novel variants were discovered, each in a single geographic region, predominantly Europe. Analyses confirmed previously known ALPL variants, identified novel variants, and characterized geographic variation in frequency and type of ALPL variants in a large population.

Does Adjunction of Autologous Osteoblastic Cells Improve the Results of Core Decompression in Early-stage Femoral Head Osteonecrosis? A Double-blind, Randomized Trial.

BACKGROUND: Osteonecrosis of the femoral head (ONFH) is a disabling disease that can ultimately progress to collapse of the femoral head, often resulting in THA. Core decompression of the femoral head combined with cell therapies have shown beneficial effects in previous clinical studies in patients with early-stage (Association Research Circulation Osseous [ARCO] Stage I and II) ONFH. However, high-quality evidence confirming the efficacy of this treatment modality is still lacking. QUESTIONS/PURPOSES: (1) Is core decompression combined with autologous osteoblastic cell transplantation superior to core decompression with placebo implantation in relieving disease-associated pain and preventing radiologic ONFH progression in patients with nontraumatic early-stage ONFH? (2) What adverse events occurred in the treatment and control groups? METHODS: This study was a Phase III, multicenter, randomized, double-blind, controlled study conducted from 2011 to 2019 (ClinicalTrails.gov registry number: NCT01529008). Adult patients with ARCO Stage I and II ONFH were randomized (1:1) to receive either core decompression with osteoblastic cell transplantation (5 mL with 20 x 10 6 cells/mL in the study group) or core decompression with placebo (5 mL of solution without cells in the control group) implantation. Thirty percent (68 of 230) of the screened patients were eligible for inclusion in the study; of these, 94% (64 of 68) underwent a bone marrow harvest or sham procedure (extended safety set) and 79% (54 of 68) were treated (study group: 25 patients; control group: 29). Forty-nine patients were included in the efficacy analyses. Similar proportions of patients in each group completed the study at 24 months of follow-up (study group: 44% [11 of 25]; control: 41% [12 of 29]). The study and control groups were comparable in important ways; for example, in the study and control groups, most patients were men (79% [27 of 34] and 87% [26 of 30], respectively) and had ARCO Stage II ONFH (76% [19 of 25] and 83% [24 of 29], respectively); the mean age was 46 and 45 years in the study and control groups, respectively. The follow-up period was 24 months post-treatment. The primary efficacy endpoint was the composite treatment response at 24 months, comprising the clinical response (clinically important improvement in pain from baseline using the WOMAC VA3.1 pain subscale, defined as 10 mm on a 100-mm scale) and radiologic response (the absence of progression to fracture stage [≥ ARCO Stage III], as assessed by conventional radiography and MRI of the hips). Secondary efficacy endpoints included the percentages of patients achieving a composite treatment response, clinical response, and radiologic response at 12 months, and the percentage of patients undergoing THA at 24 months. We maintained a continuous reporting system for adverse events and serious adverse events related to the study treatment, bone marrow aspiration and sham procedure, or other study procedures throughout the study. A planned, unblinded interim analysis of efficacy and adverse events was completed at 12 months. The study was discontinued because our data safety monitoring board recommended terminating the study for futility based on preselected futility stopping rules: conditional power below 0.20 and p = 0.01 to detect an effect size of 10 mm on the 100-mm WOMAC VA3.1 pain subscale (improvement in pain) and the absence of progression to fracture (≥ ARCO Stage III) observed on radiologic assessment, reflecting the unlikelihood that statistically beneficial results would be reached at 24 months after the treatment. RESULTS: There was no difference between the study and control groups in the proportion of patients who achieved a composite treatment response at 24 months (61% [14 of 23] versus 69% [18 of 26]; p = 0.54). There was no difference in the proportion of patients with a treatment response at 12 months between the study and control groups (14 of 21 versus 15 of 23; p = 0.92), clinical response (17 of 21 versus 16 of 23; p = 0.38), and radiologic response (16 of 21 versus 18 of 23; p = 0.87). With the numbers available, at 24 months, there was no difference in the proportion of patients who underwent THA between the study and control groups (24% [six of 25] versus 14% [four of 29]). There were no serious adverse events related to the study treatment, and only one serious adverse event (procedural pain in the study group) was related to bone marrow aspiration. Nonserious adverse events related to the treatment were rare in the study and control groups (4% [one of 25] versus 14% [four of 29]). Nonserious adverse events related to bone marrow or sham aspiration were reported by 15% (five of 34) of patients in the study group and 7% (two of 30) of patients in the control group. CONCLUSION: Our study did not show any advantage of autologous osteoblastic cells to improve the results of core decompression in early-stage (precollapse) ONFH. Adverse events related to treatment were rare and generally mild in both groups, although there might have been a potential risk associated with cell expansion. Based on our findings, we do not recommend the combination of osteoblastic cells and core decompression in patients with early-stage ONFH. Further, well-designed studies should be conducted to explore whether other treatment modalities involving a biological approach could improve the overall results of core decompression. LEVEL OF EVIDENCE: Level II, therapeutic study.

Lower limb bone geometry in adult individuals with X-linked hypophosphatemia: an observational study.

We assessed lower-limb geometry in adults with X-linked hypophosphatemia (XLH) and controls. We found large differences in multiple measures including femoral and tibial torsion, bowing and cross-sectional area and acetabular version and coverage which may contribute to clinical problems such as osteoarthritis, fractures and altered gait common in XLH. PURPOSE: Individuals with X-linked hypophosphatemia (XLH) are at risk of lower-limb deformities and early onset of osteoarthritis. These two factors may be linked, as altered biomechanics is a risk factor for osteoarthritis. This exploratory evaluation aims at providing clues and concepts for this association to facilitate future larger-scale and longitudinal studies on that aspect. METHODS: For this observational study, 13 patients with XLH, aged 18-65 years (6 female), were compared with sex-, age- and weight-matched healthy individuals at a single German research centre. Femoral and hip joint geometry, including femoral and tibial torsion and femoral and tibial shaft bowing, bone cross-sectional area (CSA) and acetabular version and coverage were measured from magnetic resonance imaging (MRI) scans. RESULTS: Total femoral torsion was 29° lower in individuals with XLH than in controls (p < 0.001), mainly resulting from lower intertrochanteric torsion (ITT) (p < 0.001). Femoral lateral and frontal bowing, tibial frontal bowing, mechanical axis, femoral mechanical-anatomical angle, acetabular version and acetabular coverage were all greater and tibial torsion lower in individuals with XLH as compared to controls (all p < 0.05). Greater femoral total and marrow cavity CSA, greater tibial marrow cavity CSA and lower cortical CSA were observed in XLH (all p < 0.05). DISCUSSION: We observed large differences in clinically relevant measures of tibia and particularly femur bone geometry in individuals with XLH compared to controls. These differences may plausibly contribute to clinical manifestations of XLH such as early-onset osteoarthritis, pseudofractures and altered gait and therefore should be considered when planning corrective surgeries.

Oral health status of adult hypophosphatasia patients: A cross-sectional study.

AIM: This study evaluated the oral health status of adult patients with hypophosphatasia (HPP). MATERIALS AND METHODS: Parameters of oral health assessment comprised decayed/missing/filled teeth (DMFT) index, probing pocket depth and clinical attachment level (CAL) as well as documentation of tooth loss and periodontal health status according to CCD/AAP criteria. Findings were compared with national reference data (DMS V survey) reporting oral health status in age-related controls. Within-group comparisons were made between the HPP patients harbouring one versus two alkaline phosphatase liver/bone/kidney type (ALPL) gene variants. RESULTS: Of 80 HPP patients (64 female) with a mean age of 46.4 years (range 24-78) and one (n = 55) or two (n = 18) variants (n = 7 lacking testing) within the ALPL gene, those with two variants displayed substantially higher tooth loss rate (14.0 ± 9.3) than those affected by only one ALPL variant (4.1 ± 5.4), who did not differ substantially from healthy DMS V controls. While DMFT score and severe periodontal diseases (PDs) of HPP patients with one variant only increased with progressing age, the two-variant sub-cohort age independently exhibited increased DMFT scores and a higher rate of severe PDs. CONCLUSIONS: HPP patients affected by two variants of the ALPL gene exhibited a higher risk of periodontitis and tooth loss than the general population, while patients with one variant developed clinically relevant oral disease symptoms with progressing ageing. CLINICALTRIALS: gov identifier: NCT02291497.

[Clavicle stress fracture following reverse shoulder arthroplasty]. / Insuffizienzfraktur der Klavikula nach Implantation einer inversen Schulterendoprothese.

We present a rare case of clavicle fracture following reverse shoulder arthroplasty (RSA). This complication may be caused by the higher tension of the deltoid muscle after RSA, similarly to stress fractures of the acromion. Associated bone disease, i.e. osteoporosis, may contribute. In the few case reports available, the affected patients showed significant functional impairments. In the current case, the fracture was addressed with plate fixation. Despite good intraoperative results, osteosynthesis failure with secondary dislocation of the fracture occurred.

[Rare bone disorders and respective treatments]. / Seltene osteologische Erkrankungen und ihre Therapie.

Delineating the genetic background and the underlying pathophysiology of rare skeletal dysplasias enables a broader understanding of these disorders as well as novel perspectives regarding differential diagnosis and targeted development of therapeutic approaches. Hypophosphatasia (HPP) due to genetically determined Alkaline Phosphatase deficiency exemplifies this development. While an enzyme replacement therapy could be established for severe HPP with the prevailing bone manifestation, the clinical impact of not immediately bone-related manifestations just being successively understood. Correspondingly, the elucidation of the pathophysiology underlying renal phosphate wasting expanded our knowledge regarding phosphate metabolism and bone health and facilitated the development of an anti-FGF-23 Antibody for targeted treatment of X­linked Hypophosphatemia (XLH). Evolutions regarding the nosology of osteogenesis imperfecta (OI) along with the identification of further causative genes also detected in the context of genetically determined osteoporosis illustrate the pathophysiologic interrelation between monogenetic bone dysplasias and multifactorial osteoporosis. While current therapeutic strategies for OI follow osteoporosis treatment, the expanding knowledge about OI forms the fundament for establishing improved treatment strategies-for both OI and osteoporosis. Similar developments are emerging regarding rare skeletal disorders like Achondroplasia, Fibrodysplasia ossificans progressive and Morbus Morquio (Mukopolysaccharidosis Type IV).

Diagnostic delay is common among patients with hypophosphatasia: initial findings from a longitudinal, prospective, global registry.

BACKGROUND: Hypophosphatasia (HPP) is a rare, systemic disease caused by mutation(s) within the ALPL gene encoding tissue-nonspecific alkaline phosphatase (ALP). HPP has a heterogeneous presentation, which coupled with its rarity, often leads to missed/delayed diagnosis and an incomplete understanding of its natural history. To better understand the epidemiology and clinical course of HPP, including timing of diagnosis after first reported manifestation, we present baseline data for patients enrolled in the Global HPP Registry. METHODS: Data were analyzed from patients with an HPP diagnosis confirmed by low serum ALP activity and/or an ALPL pathogenic variant, regardless of prior or current treatment, according to age at enrollment (children: < 18 y; adult: ≥18 y). All analyses were descriptive. RESULTS: Of 269 patients from 11 countries enrolled January 2015-September 2017, 121 (45.0%) were children and 148 (55.0%) were adults. The majority of children and adults were female (61.2 and 73.0%, respectively) and white (57.7 and 90.0%, respectively). Children had a median (min, max) age at earliest reported HPP manifestation of 7.2 months (- 2.3 mo, 16.0 y), which was > 12 months before diagnosis at age 20.4 months (- 0.2 mo, 16.0 y). In adults, the earliest reported manifestation occurred at a median (min, max) age of 37.6 years (0.2 y, 75.2 y), which preceded age at diagnosis (47.5 years [0.2 y, 75.2 y]) by ~ 10 years. Premature loss of deciduous teeth (48.2%, age ≥ 6 mo), bone deformity (32.5%), and failure to thrive (26.7%) were most commonly reported in the HPP-related disease history of children. Pain (74.5%), orthopedic procedures and therapies (44.6%), and recurrent and poorly healing fractures (36.5%) were most commonly reported in the HPP-related disease history of adults. CONCLUSIONS: The Global HPP Registry represents the largest observational study of patients with HPP, capturing real world data. This analysis shows that diagnostic delay is common, reflecting limited awareness of HPP, and that HPP is associated with systemic manifestations across all ages. Many patients diagnosed in adulthood had HPP manifestations in childhood, highlighting the importance of taking thorough medical histories to ensure timely diagnosis. TRIAL REGISTRATION: Clinicaltrials.gov : NCT02306720 , December 2014; ENCePP.eu: EUPAS13526 , May 2016 (retrospectively registered).

Physical contact between mesenchymal stem cells and endothelial precursors induces distinct signatures with relevance to the very early phase of regeneration.

Multipotent adult stem cells/precursor cells, especially of the mesenchymal and endothelial lineage, may have great potential for bone tissue engineering. Although their potential is highly recognized, not much is known about the underlying molecular mechanisms that initiate the regeneration process, connect osteogenesis, and angiogenesis and, finally, orchestrate renewal of bone tissue. Our study addressed these questions by generating two in vitro cell culture models to examine the changes in the global gene expression patterns of endothelial precursor cells and mesenchymal stem cells after 24 hours of either humoral (conditioned medium) or direct cell-cell interaction (co-culture). Endothelial precursor cells were isolated from human buffy coat and mesenchymal stem cells from the bone marrow of the femoral head. The comparison of the treated and control cells by microarray analyses revealed in total more than 1500 regulated genes, which were analyzed for their affiliation to angiogenesis and osteogenesis. Expression array analyses at the RNA and protein level revealed data with respect to regulated genes, pathways and targets that may represent a valid basis for further dissection of the systems biology of regeneration processes. It may also be helpful for the reconstitution of the natural composition of a regenerative microenvironment when targeting tissue regeneration both in vitro and in situ.

Dissection of mechanoresponse elements in promoter sites of the mechanoresponsive CYR61 gene.

Mechanotransduction is important for mesenchymal regeneration and differentiation. Exaggerated high or very low impact yields pathological outcome resulting in fracture or tissue atrophy. Pathological strain in animal models was described but tools to dissect the respective stimuli and downstream pathways are limited. We expand the analytical tools to describe DNA strain response elements in a reporter gene approach. Deletion constructs of the human cysteine-rich protein 61 (CYR61) promoter were cloned into luciferase vectors and stably transfected into human telomerase-immortalised mesenchymal stem cells (hMSC-TERT). Cells were mechanically stimulated with variable frequencies, amplitudes and durations. Promoter activity was determined as well as CYR61 mRNA and protein expression. In silico promoter analysis identified putative transcription factor binding sites, one of which was a cAMP response element, verified by electrophoretic mobility shift assay. We demonstrate for the first time that the activity of promoter regions is inhibited in low, but stimulated in high frequency stimulations. We conclude that by varying conditions of mechanical strain it is possible to characterize stimulatory versus inhibitory strain on cellular levels. Our work may be helpful in future studies to dissect the molecular pathways of physiological versus pathological strain and may have implications for clinical exercise based treatment strategies.

Monitoring guidance for patients with hypophosphatasia treated with asfotase alfa.

Hypophosphatasia (HPP) is a rare, inherited, systemic, metabolic disorder caused by autosomal recessive mutations or a single dominant-negative mutation in the gene encoding tissue-nonspecific alkaline phosphatase (TNSALP). The disease is associated with a broad range of signs, symptoms, and complications, including impaired skeletal mineralization, altered calcium and phosphate metabolism, recurrent fractures, pain, respiratory problems, impaired growth and mobility, premature tooth loss, developmental delay, and seizures. Asfotase alfa is a human, recombinant enzyme replacement therapy that is approved in many countries for the treatment of patients with HPP. To address the unmet need for guidance in the monitoring of patients receiving asfotase alfa, an international panel of physicians with experience in diagnosing and managing HPP convened in May 2016 to discuss treatment monitoring parameters. The panel discussions focused on recommendations for assessing and monitoring patients after the decision to treat with asfotase alfa had been made and did not include recommendations for whom to treat. Based on the consensus of panel members, this review provides guidance on the monitoring of patients with HPP during treatment with asfotase alfa, including recommendations for laboratory, efficacy, and safety assessments and the frequency with which these should be performed during the course of treatment. Recommended assessments are based on patient age and include regular monitoring of biochemistry, skeletal radiographs, respiratory function, growth, pain, mobility and motor function, and quality of life. Because of the systemic presentation of HPP, a coordinated, multidisciplinary, team-based, patient-focused approach is recommended in the management of patients receiving asfotase alfa. Monitoring of efficacy and safety outcomes must be tailored to the individual patient, depending on medical history, clinical manifestations, availability of resources in the clinical setting, and the clinician's professional judgment.

Cellular pharmacodynamic effects of Pycnogenol® in patients with severe osteoarthritis: a randomized controlled pilot study.

BACKGROUND: The standardized maritime pine bark extract (Pycnogenol®) has previously shown symptom alleviating effects in patients suffering from moderate forms of knee osteoarthritis (OA). The cellular mechanisms for this positive impact are so far unknown. The purpose of the present randomized pilot controlled study was to span the knowledge gap between the reported clinical effects of Pycnogenol® and its in vivo mechanism of action in OA patients. METHODS: Thirty three patients with severe OA scheduled for a knee arthroplasty either received 100 mg of Pycnogenol® twice daily or no treatment (control group) three weeks before surgery. Cartilage, synovial fluid and serum samples were collected during surgical intervention. Relative gene expression of cartilage homeostasis markers were analyzed in the patients' chondrocytes. Inflammatory and cartilage metabolism mediators were investigated in serum and synovial fluid samples. RESULTS: The oral intake of Pycnogenol® downregulated the gene expression of various cartilage degradation markers in the patients' chondrocytes, the decrease of MMP3, MMP13 and the pro-inflammatory cytokine IL1B were statistically significant (p ≤ 0.05). Additionally, protein concentrations of ADAMTS-5 in serum were reduced significantly (p ≤ 0.05) after three weeks intake of the pine bark extract. CONCLUSIONS: This is the first report about positive cellular effects of a dietary supplement on key catabolic and inflammatory markers in patients with severe OA. The results provide a rational basis for understanding previously reported clinical effects of Pycnogenol® on symptom scores of patients suffering from OA. TRIAL REGISTRATION: ISRCTN10754119 . Retrospectively registered 08/10/2015.

Recombinant Enzyme Replacement Therapy in Hypophosphatasia.

Hypophosphatasia (HPP) is a rare monogenetic and multisystemic disease with involvement of different organs, including bone, muscle, kidney, lung, gastrointestinal tract and the nervous system. The exact metabolic mechanisms of the effects of TNAP deficiency in different tissues are not understood in detail. There is no approved specific treatment for HPP; therefore symptomatic treatment in order to improve the clinical features is of major interest. Enzyme replacement therapy (ERT) is a relatively new type of treatment based on the principle of administering a medical treatment replacing a defective or absent enzyme. Recently ERT with a bone targeted recombinant human TNAP molecule has been reported to be efficient in ten severely affected patients and improved survival of life threatening forms. These results are very promising especially with regard to the skeletal phenotype but it is unclear whether ERT also has beneficial effects for craniosynostosis and in other affected tissues in HPP such as brain and kidney. Long-term data are not yet available and further systematic clinical trials are needed. It is also necessary to establish therapeutic approaches to help patients who are affected by less severe forms of HPP but also suffer from a significant reduction in quality of life. Further basic research on TNAP function and role in different tissues and on its physiological substrates is critical to gain a better insight in the pathogenesis in HPP. This and further experiences in new therapeutic strategies may improve the prognosis and quality of life of patients with all forms of HPP.

Effectiveness of asfotase alfa for treatment of adults with hypophosphatasia: results from a global registry.

BACKGROUND: Hypophosphatasia (HPP) is a rare inherited disease caused by deficient activity of tissue-nonspecific alkaline phosphatase. Many adults with HPP have a high burden of disease, experiencing chronic pain, fatigue, limited mobility, and dental issues, contributing to decreased health-related quality of life (HRQoL). HPP may be treated with the enzyme replacement therapy asfotase alfa though real-world data in adults are limited. This analysis was conducted to assess the clinical effectiveness of asfotase alfa among adults in the Global HPP Registry. METHODS: The Global HPP Registry is an observational, prospective, multinational study. Adults ≥ 18 years of age were included in this analysis if they had serum alkaline phosphatase (ALP) activity below the age- and sex-adjusted reference ranges, and/or ALPL variant(s), and received asfotase alfa for ≥ 6 months. Mobility was assessed with the 6-Minute Walk Test (6MWT), and patient-reported outcomes tools were used to assess pain (Brief Pain Inventory-Short Form), quality of life (36-item Short Form Health Survey, version 2 [SF-36v2]), and disability (Health Assessment Questionnaire-Disability Index) at multiple time points from baseline through Month 36. Data were collected as per usual standard of care; patients may not have contributed data at all time points. RESULTS: A total of 190 patients met the inclusion criteria. For patients with ≥ 1 follow-up measurement, the mean distance achieved on 6MWT increased from 404 m (range 60-632 m) at baseline (n = 31) to 484 m at Month 12 (range 240-739 m; n = 18) and remained above baseline through Month 36 (n = 7). Improvements in mean self-reported pain severity scores ranged from - 0.72 (95% CI: - 1.23, - 0.21; n = 38) to - 1.13 (95% CI: - 1.76, - 0.51; n = 26) and were observed at all time points. Improvements in the Physical Component Summary score of SF-36v2 were achieved by Month 6 and sustained throughout follow-up. There was a trend toward improvement in the Mental Component Summary score of SF-36v2 at most time points, with considerable fluctuations from Months 12 (n = 28) through 36 (n = 21). The most frequent adverse events were injection site reactions. CONCLUSIONS: Adults with HPP who received asfotase alfa for ≥ 6 months experienced improvements in mobility, physical function, and HRQoL, which were maintained over 3 years of follow-up. REGISTRATION: NCT02306720; EUPAS13514.

The Global ALPL gene variant classification project: Dedicated to deciphering variants.

BACKGROUND: Hypophosphatasia (HPP) is an inherited multisystem disorder predominantly affecting the mineralization of bones and teeth. HPP is caused by pathogenic variants in ALPL, which encodes tissue non-specific alkaline phosphatase (TNSALP). Variants of uncertain significance (VUS) cause diagnostic delay and uncertainty amongst patients and health care providers. RESULTS: The ALPL gene variant database (https://alplmutationdatabase.jku.at/) is an open-access archive for interpretation of the clinical significance of variants reported in ALPL. The database contains coding and non-coding variants, including single nucleotide variants, insertions/deletions and structural variants affecting coding or non-coding sequences of ALPL. Each variant in the database is displayed with details explaining the corresponding pathogenicity, and all reported genotypes and phenotypes, including references. In 2021, the ALPL gene variant classification project was established to reclassify VUS and continuously assess and update genetic, phenotypic, and functional variant information in the database. For this purpose, the database provides a unique submission system for clinicians, geneticists, genetic counselors, and researchers to submit VUS within ALPL for classification. An international, multidisciplinary consortium of HPP experts has been established to reclassify the submitted VUS using a multi-step process adhering to the stringent ACMG/AMP variant classification guidelines. These steps include a clinical phenotype assessment, deep literature research including artificial intelligence technology, molecular genetic assessment, and in-vitro functional testing of variants in a co-transfection model to measure ALP residual activity. CONCLUSION: This classification project and the ALPL gene variant database will serve the global medical community, widen the genotypic and phenotypic HPP spectrum by reporting and characterizing new ALPL variants based on ACMG/AMP criteria and thus facilitate improved genetic counseling and medical decision-making for affected patients and families. The project may also serve as a gold standard framework for multidisciplinary collaboration for variant interpretation in other rare diseases.

Impact of Restricted Phosphorus, Calcium-adjusted Diet on Musculoskeletal and Mental Health in Hypophosphatasia.

Context: Impairments in musculoskeletal and mental health are common in adults with Hypophosphatasia (HPP). Restricted phosphorus intake has been suggested to positively affect symptoms in HPP, but there is a lack of interventional evidence. Objective: This work aimed to evaluate the effect of a phosphorus-restricted, calcium-adjusted diet on musculoskeletal and mental health in HPP. Methods: A prospective, noncontrolled, single-center interventional study (NuSTEPS II) was conducted among outpatients at the Osteology Department, University of Wuerzburg, Germany. A total of 26 adults with an established HPP diagnosis received a standardized diet with a defined daily intake of phosphorus (1160-1240 mg/d) and calcium (870-930 mg/d) over 8 weeks. Main outcome measures were functional testing and patient-reported outcome measures. Results: At 8 weeks, significant improvements were observed in usual gait speed (P = .028) and the chair-rise test (P = .019), while no significant changes were seen in the 6-minute walk test (P = .468) and the timed up-and-go test (P = .230). Pain was not significantly reduced according to the visual analog scale (VAS) (P = .061), pain subscale of the 36-Item Short-Form Health Survey (SF-36) (P = .346), and Pain Disability Index (P = .686). Further, there was a significant improvement in the SF-36 vitality subscale (P = .022) while all other subscales as well as the Lower Extremity Functional Scale (P = .670) and the Fatigue Assessment Scale (P = .392) did not change significantly. Adjustments of mineral intake were not associated with relevant alterations regarding the intake of energy and energy-supplying nutrients or body composition. Conclusion: Adjusting phosphorus and calcium intake may positively affect individual symptoms in adults with HPP, but overall clinical effectiveness regarding major issues like pain and endurance appears limited.

Effects of asfotase alfa in adults with pediatric-onset hypophosphatasia over 24 months of treatment.

BACKGROUND: Hypophosphatasia (HPP) is a rare, heritable metabolic disorder caused by deficient activity of tissue-nonspecific alkaline phosphatase (TNSALP). Asfotase alfa (AA) is a human recombinant TNSALP that promotes bone mineralization and is approved to treat eligible patients with HPP. METHODS: This prospective single-center observational study evaluated AA in adults with pediatric-onset HPP over 2 years of treatment (ClinicalTrials.govNCT03418389). Primary outcomes evaluated physical function; secondary outcomes assessed quality of life (QoL) and pain. RESULTS: The study included 17 females and 5 males (mean age: 48.7 years). Median distance walked in the 6-Minute Walk Test increased significantly from baseline to 12 months (P = 0.034) and results were sustained. Median Timed Up and Go test time significantly decreased from baseline at 12 (P = 0.003) and 24 months (P = 0.005), as did the median chair rise time test at 12 (P = 0.003) and 24 months (P < 0.002). The change from baseline in usual gait speed was significant at 12 (P = 0.003) and 24 months (P = 0.015). Mean dominant and nondominant hand grip strength improved at 24 months (P = 0.029 and P = 0.019, respectively). Median Short Form 36 Physical Component Summary scores significantly improved from baseline at 12 (P = 0.012) and 24 (P = 0.005) months, and median Lower Extremity Functional Scale scores improved from baseline at 12 (P = 0.001) and 24 (P = 0.002) months. No significant change was noted in pain level at these timepoints. While injection site reactions occurred in 86.4 % of the participants, there were no severe side effects or safety findings. CONCLUSIONS: Adults with pediatric-onset HPP treated with AA experienced marked improvement in functional and QoL outcomes that were observed as early as within 3 months of initial treatment and were sustained over 24 months.