Intracranial aneurysm as a possible complication of osteogenesis imperfecta: a case series and literature review.

Osteogenesis imperfecta (OI) is an inherited disease characterized by bone fragility due to impaired type I collagen. Although orthopedic management is improving, other complications are poorly understood. We describe three patients with OI with unruptured intracranial aneurysm (IA) detected by magnetic resonance angiography (MRA) screening of 14 patients. Case 1 was a 73-year-old woman with type 1 OI with blue sclera, vertebral compression fractures, and impaired hearing. Lumbar spine bone mineral density (BMD) was preserved (young adult mean (YAM): 86%). MRA revealed an IA in the right internal carotid artery. Case 2 was a 43-year-old man with type 4 OI and leg-length discrepancy due to left femoral neck fracture. Lumbar spine BMD was decreased (YAM: 61%). MRA showed an IA in the left anterior cerebral artery. Case 3 was a 35-year-old woman with type 3 OI with blue sclera, dentinogenesis imperfecta, deformity of the long bones, and severe scoliosis. She had undergone spine surgery and needed wheelchair assistance. The YAM of the femoral neck BMD was 71%. MRA indicated an IA in the right posterior communicating artery. The prevalence of IA in our series of patients with OI was 21%, which is higher than the reported prevalence of unruptured IA in the Japanese general population (2.2%), suggesting that IA may be a complication of OI. Our literature review revealed no cases of OI with unruptured IA, but 11 cases of OI with subarachnoid hemorrhage. IA seems unrelated to OI type, sex, or age. We recommend MRA of adults with OI.

Clinical performance of a novel chemiluminescent enzyme immunoassay for FGF23.

INTRODUCTION: Measurement of fibroblast growth factor 23 (FGF23) has been reported to be clinically useful for the differential diagnosis of chronic hypophosphatemia. However, assays for research use only are available in Japan. Thus, the objective of this study was to examine the clinical utility of a novel and automated chemiluminescent enzyme immunoassay for the measurement of FGF23. MATERIALS AND METHODS: Participants were recruited from July 2015 to January 2017 at six facilities in Japan. Thirty-eight patients with X-linked hypophosphatemic rickets (XLH 15 males, 23 females, age 0-66 years), five patients with tumour-induced osteomalacia (TIO 3 males, 2 females, age 60-73 years), and twenty-two patients with hypophosphatemia (11 males, 11 females, age 1-75 years) caused due to other factors participated in this study. RESULTS: With the clinical cut-off value of FGF23 at 30.0 pg/mL indicated in the Diagnostic Guideline of Rickets/Osteomalacia in Japan, the sensitivity and specificity of FGF23-related hypophosphatemic rickets/osteomalacia without vitamin D deficiency (disease group-1) were 100% and 81.8%, respectively, which distinguished it from non-FGF23-related hypophosphatemia (disease group-2). Furthermore, the diagnostic sensitivity of FGF23-related hypophosphatemia with vitamin D deficiency remained at 100%. Among the four patients with FGF23 levels ≥ 30.0 pg/mL in disease group-2, two patients with relatively higher FGF23 values were suspected to have genuine FGF23-related hypophosphatemia, due to the ectopic production of FGF23 in pulmonary and prostate small cell carcinomas. CONCLUSION: The novel FGF23 assay tested in this study is useful for the differential diagnosis of hypophosphatemic rickets/osteomalacia in a clinical setting.

Final adult height in long-term growth hormone-treated achondroplasia patients.

The objective of this study was to evaluate the gain in final height of achondroplasia (ACH) patients with long-term growth hormone (GH) treatment. We analyzed medical data of 22 adult patients (8 males and 14 females) treated with GH at a dose of 0.05 mg/kg/day. Optionally, tibial lengthening (TL) was performed with the Ilizalov method in 15 patients and TL as well as femoral lengthening (FL) in 6 patients. Concomitant gonadal suppression therapy with buserelin acetate was applied in 13 patients. The mean treatment periods with GH were 10.7 ± 4.0 and 9.3 ± 2.5 years for males and females, respectively. GH treatment augmented the final height +0.60 ± 0.52 SD (+3.5 cm) and +0.51 ± 1.29 SD (+2.8 cm) in males and females compared to non-treated ACH patients, respectively. Final height of ACH patients that underwent GH and TL increased +1.72 ± 0.72 SD (+10.0 cm) and +1.95 ± 1.34 SD (+9.8 cm) in males and females, respectively. GH, TL, and FL increased their final height +2.97 SD (+17.2 cm) and +3.41 ± 1.63 SD (+17.3 cm) in males and females, respectively. Gonadal suppression therapy had no impact on final height. CONCLUSIONS: Long-term GH treatment contributes to 2.6 and 2.1% of final adult height in male and female ACH patients, respectively.

An observational study of the effectiveness and safety of growth hormone (Humatrope(®)) treatment in Japanese children with growth hormone deficiency or Turner syndrome.

This study assessed the effectiveness and safety of growth hormone (GH; Humatrope(®)) therapy in Japanese children with GH deficiency (GHD) or Turner syndrome (TS) enrolled in the Genetics and Neuroendocrinology of Short Stature International Study (GeNeSIS). GeNeSIS is an open-label, multinational, multicenter, observational study conducted in 30 countries. In this interim report, there were 1129 GH treatment-naïve children with GHD, with a mean chronological age (± standard deviation) of 8.75 (3.32) years, and 90 girls with TS, with a mean chronological age of 8.93 (3.67) years. The mean height standard deviation score (SDS) increased from -2.73 (0.63) SD and -2.71 (0.63) SD at study entry to -2.22 (0.68) SD and -2.20 (0.60) SD after 1 year of treatment in the GHD and TS groups, respectively. In both groups, mean height SDS increased further with each year of treatment to 4 years; however, the magnitude of change in height SDS declined with time. The mean insulin-like growth factor-I SDS increased from below the mean of the reference population at study entry to a level similar to (GHD group) or higher than (TS group) the mean of the reference population during the 4-year treatment period. The incidence of serious adverse events (AEs), treatment-related AEs, and AEs related to glucose intolerance was low in both groups (0.1% to 3.0%). In conclusion, GH treatment in Japanese children with GHD or TS resulted in increased growth over a 4-year treatment period with a favorable safety profile; however, the improvements in growth declined with time.

A case of autosomal dominant osteopetrosis type II with a novel TCIRG1 gene mutation.

Osteopetrosis is a rare genetic disorder characterized by increased bone mineral density (BMD) due to osteoclast failure. T-cell immune regulator 1 (TCIRG1) plays crucial roles on osteoclast function, and its mutation causes autosomal recessive osteopetorosis. However, mutations in TCIRG1 have never been identified in autosomal dominant osteopetrosis (ADO). A 3-year-old boy was first presented to the clinic because of spontaneous radius and femur fractures. He has optic atrophy. The areal BMD at the lumbar spine was 1274 g/cm2 (233% of normal). Laboratory tests revealed no remarkable abnormal findings, including anemia, except for extremely elevated serum tartrate-resistant acid phosphatase-5b (14,600 mU/dL). Radiographically, the skull base, pelvis, and vertebrae showed a focal sclerosis. Genetic analysis revealed a novel de novo heterozygous missense mutation (His242Arg). Taken together with the mutation, his mild clinical features were diagnosed as ADO. This case implies that TCIRG1 could become a genetic candidate for ADO in addition to malignant forms such as ARO.

Self-Administration of Burosumab in Children and Adults with X-Linked Hypophosphataemia in Two Open-Label, Single-Arm Clinical Studies.

INTRODUCTION: X-linked hypophosphataemia (XLH) is a rare, genetic renal phosphate-wasting disease, resulting from excess fibroblast growth factor 23 (FGF23) activity, which has a progressive and profound impact on patients throughout life. The monoclonal anti-FGF23 antibody, burosumab, is a subcutaneous injection indicated for the treatment of XLH in children and adults. Originally, burosumab was approved to be administered by a healthcare professional (HCP), but the option of self-administration would enable patient independence and easier access to treatment. Two open-label, single-arm clinical trials, conducted in Japan and Korea, have assessed the safety and efficacy of self-administration of burosumab in both children and adults with XLH. METHODS: In KRN23-003 (n = 15 children aged 1-12 years) and KRN23-004 (n = 5 children aged 3-13 years, n = 4 adults aged 21-65 years), children initially received 0.8 mg/kg of burosumab every 2 weeks and adults initially received 1.0 mg/kg of burosumab every 4 weeks. Self-administration was permitted from Week 4, and patients or carers were provided with training to inject correctly. RESULTS: In both trials, burosumab had an acceptable safety profile with mainly mild-to-moderate adverse events. Following self-administration, no patients reported serious treatment-emergent adverse events ≥ grade 3, injection-site reactions or hypersensitivity reactions related to burosumab. Serum phosphate and active vitamin D levels increased from baseline in children and adults. CONCLUSIONS: These results indicated that the efficacy and safety of burosumab when administered either by a carer or patient are similar to that when administered by an HCP and show that self-administration is a viable option for patients with XLH. TRIAL REGISTRATION NUMBERS: NCT03233126 and NCT04308096.

Japanese growth prediction model for prepubertal children with growth hormone deficiency.

BACKGROUND: Individual responses to growth hormone (GH) treatment are variable, and efficacy should be judged in each individual patient. OBJECTIVE: The aim of this study was to develop a prediction model for the growth response of GH treatment in Japanese prepubertal children with GH deficiency. PATIENTS AND METHODS: Pediatric patients with GH deficiency were enrolled. Auxological measurements, markers of GH status, and markers of bone metabolism were measured at baseline and at 3 and 6 months after the start of GH treatment. Correlations with height velocity (HV) at 36 months of GH treatment were calculated. Prediction models were evaluated by multiple regression analysis. RESULTS: The model, which combined the parameters of HV at 3 months, insulin-like growth factor-binding protein 3, standard deviation score, and pyridinoline at 3 months, best predicted HV at 36 months. CONCLUSIONS: This model can accurately predict the first 3 years of growth response after 3 months of GH replacement therapy in prepubertal Japanese children.

Safety and Efficacy of Burosumab in Pediatric Patients With X-Linked Hypophosphatemia: A Phase 3/4 Open-Label Trial.

Objective: Burosumab, an anti-fibroblast growth factor 23 antibody, was recently approved for the treatment of X-linked hypophosphatemia (XLH).We evaluated the safety and efficacy of burosumab in pediatric XLH patients. Methods: This open-label, phase 3/4 trial of ≤ 124 weeks' duration was conducted at 4 Japanese medical centers. Fifteen children aged 1 to 12 years with XLH were included. All had previously been treated with phosphorus or vitamin D. Subcutaneous burosumab was administered every 2 weeks, starting with 0.8 mg/kg, and adjusted based on serum phosphorus levels and any safety concerns (maximum 2 mg/kg). Safety assessments included the frequency of treatment-emergent adverse events (TEAEs). Efficacy of burosumab on biochemical markers, clinical markers of rickets, motor function, and growth was also evaluated. Results: The average treatment duration was 121.7 weeks. Frequently reported TEAEs were nasopharyngitis (46.7%), dental caries (40.0%), and influenza (33.3%). At baseline, patients had low serum phosphorus concentrations (2.6 ±â€…0.3 mg/dL) and low-to-normal 1,25-dihydroxyvitamin D concentrations (24.7 ±â€…12.7 pg/mL), which increased with burosumab treatment and were maintained during the study period. Alkaline phosphatase decreased continuously. At baseline, the mean ±â€…SD total Thacher Rickets Severity Score (RSS) was 1.3 ±â€…1.2, and 4 patients (26.7%) had an RSS ≥ 2.0. Mean Radiographic Global Impression of Change and RSS tended to improve, particularly in patients with higher baseline RSS. There was a trend toward increased 6-minute walk test distance. No apparent changes in growth rate were observed. Conclusion: Burosumab has a good safety profile and is effective in pediatric patients with XLH.

Adult height after growth hormone treatment in Japanese children with idiopathic growth hormone deficiency: analysis from the KIGS Japan database.

OBJECTIVE: To identify factors affecting adult height in Japanese patients with idiopathic growth hormone deficiency (GHD), who received growth hormone (GH) treatment during childhood. METHODS: A retrospective pharmaco-epidemiological study of the effect of GH treatment on adult height standard deviation scores (SDS) was conducted in 374 Japanese patients with idiopathic GHD. During childhood, GH (0.146 +/- 0.023 mg/kg/week) was administered for a mean of 6.4 +/- 2.6 years. RESULTS: The mean adult height was 160.6 +/- 6.3 cm (-1.75 SD; n = 232) in boys and 146.9 +/- 7.3 cm (-2.20 SD; n = 158) in girls after GH therapy. The mean increases in height SDS in boys and girls with severe GHD were 2.13 SD and 1.66 SD, respectively (p < 0.05). These increases were greater than those observed in patients with moderate GHD and mild GHD. The mean adult height of male patients with GHD and gonadotropin deficiency (166.8 cm) was significantly higher (p < 0.05) than that of isolated GHD patients who were either receiving (159.1 cm) or not receiving (160.5 cm) gonadal suppression therapy. The mean adult heights of female patients were 149.6, 146.7, and 146.9 cm, respectively, and these values did not significantly differ. CONCLUSION: Linear multiple regression analyses of Japanese patients with severe GHD (n = 61) revealed three independent variables that influenced adult height: gonadotropin deficiency, initial height SDS and height velocity during the first year after the initiation of GH therapy.

Switching from conventional therapy to burosumab injection has the potential to prevent nephrocalcinosis in patients with X-linked hypophosphatemic rickets.

OBJECTIVES: X-linked hypophosphatemic rickets (XLH) is a congenital fibroblast growth factor (FGF)23-related metabolic bone disease that is treated with active vitamin D and phosphate as conventional therapies. Complications of these therapies include nephrocalcinosis (NC) caused by excessive urine calcium and phosphate concentrations. Recently, an anti-FGF23 antibody, burosumab, was developed and reported to be effective in poorly-controlled or severe XLH patients. This study aimed to reveal the impact of switching treatments in relatively well-controlled XLH children with the Rickets Severity Scale less than 2.0. METHODS: The effects of the two treatments in eight relatively well-controlled XLH children with a mean age of 10.4 ± 1.9 years were compared retrospectively for the same treatment duration (31 ± 11 months) before and after the baseline. RESULTS: Actual doses of alfacalcidol and phosphate as conventional therapy were 150.9 ± 43.9 ng/kg and 27.5 ± 6.3 mg/kg per day, respectively. Renal echography revealed spotty NC in 8/8 patients, but no aggravation of NC was detected by switching treatments. Switching treatments increased TmP/GFR (p=0.002) and %TRP (p<0.001), and improved the high urine calcium/creatinine ratio to the normal range (p<0.001) although both treatments controlled disease markers equally. Additionally, low intact parathyroid hormone during conventional therapy was increased within the normal range by switching treatments. CONCLUSIONS: Our results suggest that a high dose of alfacalcidol was needed to control the disease, but it caused hypercalciuria and NC. We concluded that switching treatments in relatively well-controlled XLH children improved renal phosphate reabsorption and decreased urine calcium extraction, and may have the potential to prevent NC.

Interim Analysis of a Phase 2 Open-Label Trial Assessing Burosumab Efficacy and Safety in Patients With Tumor-Induced Osteomalacia.

Patients with tumor-induced osteomalacia (TIO), an acquired paraneoplastic condition characterized by osteomalacia due to hypophosphatemia, exhibit a similar clinical picture to those with X-linked hypophosphatemic rickets/osteomalacia (XLH). The human monoclonal anti-fibroblast growth factor 23 (FGF23) antibody burosumab (KRN23) increases serum phosphate and improves bone turnover, fracture healing, pain, and physical function in XLH patients by inhibiting circulating FGF23; thus, burosumab is expected to be an effective treatment for TIO. We report here an interim analysis of a multicenter, open-label, intraindividual dose-adjustment study of burosumab (0.3 to 2.0 mg/kg every 4 weeks) in Japanese and Korean TIO patients. The primary endpoint was the fasting serum phosphate level at each visit. Key secondary endpoints were changes over time in bone biomarkers, pharmacodynamic markers, bone histomorphometric parameters, motor function, and patient-reported outcomes. Safety was assessed based on treatment-emergent adverse events (TEAEs). Thirteen patients received burosumab treatment, of whom 4 underwent bone biopsy. The mean dose after week 112 was approximately 1.0 mg/kg. After the first burosumab administration, mean serum phosphate levels increased and remained above the lower limit of normal and in the normal range from weeks 14 to 112. Bone biomarkers initially increased, reaching maximum values at week 16 or 24, and then gradually decreased. After burosumab treatment, patients were able to walk further (evaluated by the 6-minute walk test), reported decreased pain levels, and showed a tendency toward healing of baseline fractures and pseudofractures. Two patients discontinued, one each due to disease progression and consent withdrawal. Burosumab was generally well tolerated, with no treatment-related TEAEs of grade ≥3 and no treatment-related serious AEs. In conclusion, the interim results of this first study of burosumab to treat TIO patients indicate that this drug has the potential to provide clinical benefit for patients with unresectable tumors. The full study results are eagerly anticipated. © 2020 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR)..

Monthly intravenous alendronate treatment can maintain bone strength in osteogenesis imperfecta patients following cyclical pamidronate treatment.

Objectives Osteogenesis imperfecta (OI) is a skeletal dysplasia characterized by recurrent fractures due to congenital bone fragility. The only bisphosphonate approved for OI in Japan is pamidronate (PAM). To investigate whether monthly intravenous alendronate (ALN) infusions can maintain bone strength in OI children following cyclical PAM treatment. Methods A prospective and non-inferiority study was conducted. Eight school-age OI patients aged 8.5±2.0 years who were treated with cyclical PAM for 6.0±2.3 years were enrolled and switched to monthly intravenous ALN (0.030 mg/kg/month). Changes in L1-4 bone mineral density (BMD) Z-scores, fracture rates, and bone turnover markers for 12 months were analyzed. Results Average BMD Z-scores were -3.0±1.9, -2.9±2.0, and -2.2±2.0 in 12 months before enrollment, at enrollment, and after 12 months of ALN treatment, respectively. BMD Z-scores increased significantly during treatment with both PAM and ALN (p=0.012), and the effect of ALN was not inferior to that of PAM (p=0.67). There was no change in fracture rates (p=0.86) and bone turnover markers during the 12 months before and after enrollment. Additionally, ALN showed no remarkable side effects. Conclusions Our results suggest that monthly intravenous ALN can maintain bone strength after primary usage of cyclical PAM. We concluded that monthly intravenous ALN as a maintenance treatment following cyclical PAM administration can be an option for OI children.

Growth of infants with osteogenesis imperfecta treated with bisphosphonate.

BACKGROUND: Osteogenesis imperfecta (OI) is a heritable bone disease characterized by bone brittleness and various degrees of growth disorder. Cyclic pamidronate therapy is reportedly useful to prevent bone fracture in OI and in infants with OI, but, it remains unclear how infants with OI grow during bisphosphonate therapy. METHODS: Height and weight measurements of OI infants treated with cyclic pamidronate therapy were taken before and every 6 months during therapy until 18 months. Vertebral morphometry and the concavity index were analyzed using X-ray films taken simultaneously. RESULTS: Among OI patients, those in the group for which the height z-score decreased tended to have more femur fractures than those of the group for which the height z-score increased. Morphometry of the lumbar spine showed that compression fractures occurred less during cyclic pamidronate therapy, by which the lumbar bone mineral density increased. CONCLUSIONS: Bisphosphonate preserved vertebral morphometry during 18 months after starting therapy in infants. Prevention of femur fracture during the infantile period might help prevent short stature; therapeutic strategies during infancy must better emphasize prevention of long bone fracture before the beginning of gait.

[Updated treatment of achondroplasia].

In achondroplasia, the mutation is an almost non-variable mutation in the transmembrane part of the receptor, G1138A/C, giving rise to a change in the amino acid sequence at position 380 in the protein (glycine to an arginine residue transition- Gly380Arg [G380R] . In hypochondroplasia, about 30-70% of individuals have been reported to be heterozygous for a mutation in the FGFR3 gene. The most common mutation found is the Asn540Lys (asparagine to lysine transition-N540K) in the intracellular tyrosine-kinase (TK1) region. GH Treatment significantly increased height, growth velocity and z-score of growth velocity GH therapy was more effective in hypochondroprasia than in achondroplasia. Increasing stature in individuals with skeletal dysplasias can also be accomplished by surgical leg lengthening.

First-in-Asian Phase I Study of the Anti-Fibroblast Growth Factor 23 Monoclonal Antibody, Burosumab: Safety and Pharmacodynamics in Adults With X-linked Hypophosphatemia.

X-linked hypophosphatemia (XLH) is a disease caused by abnormally elevated FGF23 levels, which cause persistent hypophosphatemia accompanied by subsequent reduction in bone mineralization that presents as rickets or osteomalacia. Burosumab is a fully human monoclonal antibody targeting FGF23 that is under development for the treatment of FGF23-related hypophosphatemia including XLH. The safety, tolerability, and proof of concept of burosumab have been evaluated in patients with XLH in previous studies conducted in countries outside of Asia. The objective of this study was to evaluate the safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD), and expression of anti-drug antibodies in Japanese and Korean adults with XLH. This was a multicenter, sequential dose-escalation, open-label, single-dose study. This study began with cohort 1 (s.c. dose of burosumab 0.3 mg/kg), after which the dose was escalated sequentially in cohort 2 (s.c. dose of burosumab 0.6 mg/kg) and cohort 3 (s.c. dose of burosumab 1.0 mg/kg). The PK of burosumab were linear within the dose range of 0.3 to 1.0 mg/kg. The PD effects such as serum phosphorus concentration, serum 1,25[OH]2D3 concentration, and ratio of tubular maximum reabsorption rate of phosphate to glomerular filtration rate (TmP/GFR) were elevated after a single s.c. administration. The area under the receiver-operating characteristic curve from 0 to t (AUC0-t) values calculated using the change from baseline values of serum phosphorus, serum 1,25(OH)2D3, and TmP/GFR were correlated with the AUC0-t of burosumab. Furthermore, no serious adverse events (AEs), deaths, remarkable increase or decrease in the corrected calcium or intact PTH levels, or signs of nephrocalcinosis or its worsening were observed after treatment. Some AEs and drug-related AEs were observed; however, there were no clinically meaningful tendencies. The positive effects and acceptable safety profile seen in this study are encouraging for Japanese and Korean patients with XLH.

Efficacy and safety of growth hormone treatment in children born small for gestational age in Japan.

Growth-promoting effects and safety of growth hormone (GH) treatment in prepubertal short-statured children born small for gestational age (SGA) were evaluated in a multicenter, open-label, randomized parallel-group comparison study. Patients were randomized to two dose groups; 34 and 33 patients received GH at 0.033 and 0.067 mg/kg/day for one year, respectively. The increase of the mean height velocity standard deviation score (SDS) was significantly (p <0.0001) higher in the 0.067-mg group (from -1.4 to 4.7) than that in the 0.033-mg group (-1.9 to 2.6). A significant (p <0.0001) increase in the mean height SDS was established in the 0.067-mg group; increases of -3.1 to -2.5 vs -3.1 to -2.2 in the 0.033- and 0.067-mg groups, respectively. The trial was non-eventful. Oral glucose tolerance tests indicated a mostly normal pattern of plasma glucose before and after 12-month GH treatment. The growth-promoting effect was significantly higher with GH treatment at 0.067 mg/kg/day.

Efficacy and safety of growth hormone treatment in Japanese children with small-for-gestational-age short stature in accordance with Japanese guidelines.

The efficacy and safety of recombinant human GH (rhGH) treatment were assessed in Japanese children with small-for-gestational-age short stature. A total of 88 patients were enrolled in the comparative and extension studies. At the end of the comparative study (24 mo), the mean height SD score for chronological age had significantly increased in the 0.23 mg/kg/wk and 0.47 mg/kg/wk groups with increments of 0.84 ± 0.42 and 1.50 ± 0.44 SD, respectively. In the extension study, the dose could be increased based on the pre-defined growth criteria. Increments in height SD scores over the 24 to 36 mo period at doses of 0.23 mg/kg/wk, 0.23 to 0.47 mg/kg/wk, and 0.47 mg/kg/wk were 0.25 ± 0.28, 0.46 ± 0.21, and 0.28 ± 0.16 SD, respectively. The growth effect increased following dose escalation even in the low responders in the initial 2-yr treatment at 0.23 mg/kg/wk, indicating the effectiveness of dose escalation in accordance with the Japanese guidelines. rhGH at 0.47 mg/kg/wk provided a greater degree of growth promotion after 24 mo. The safety profile appeared to be tolerable and was similar in all groups. Considering the increased insulin resistance, the recommendations of the regulatory authorities should be followed to minimize the risks of rhGH treatment.

A case of perinatal hypophosphatasia with a novel mutation in the ALPL gene: clinical course and review of the literature.

Hypophosphatasia (HPP) is a metabolic bone disease characterized by failure of bone calcification and vitamin B6 dependent seizures. It is caused by loss-of-function mutations in the ALPL gene. A newborn girl required respiratory support by nasal-directional positive airway pressure at birth, and pyridoxine hydrochloride administration for vitamin B6-dependent seizures observed from day two. Umbilical cord blood showed low alkaline phosphatase (ALP) activity and high pyridoxal phosphate levels. Radiographs showed severe rickets-like appearance of the bones. Genetic analysis of the ALPL gene revealed compound heterozygous mutations, c.1559delT/p.Ser188Pro. We diagnosed her with perinatal severe HPP, and started the patient on asfotase alfa from day six. Following enzyme replacement therapy (ERT), skeletal mineralization and respiratory insufficiency improved with no remarkable side-effects. Crying vital capacity (CVC) was used to evaluate respiratory status, which continuously improved from 13.3 mL/kg (day 22) to 20.6 mL/kg (day 113). Since no seizures occurred, pyridoxine hydrochloride was tapered off at one year of age. Strategies to manage perinatal severe HPP cases following ERT have not been established till date. A review of the literature shows that CVC may be a good indicator for weaning from ventilatory support. In addition, ERT will most likely enable withdrawal of pyridoxine treatment.

PTH has the potential to rescue disturbed bone growth in achondroplasia.

INTRODUCTION: Achondroplasia (Ach), the most common form of short-limb short stature, and related disorders are caused by constitutively active point mutations in the fibroblast growth factor receptor 3 (FGFR3) gene. Recent studies have provided a large body of evidence for the role of the proliferation and differentiation of chondrocytes in these disorders. Furthermore, a G380R mutation in FGFR3 (FGFR3(Ach)), which results in achondroplasia, induces apoptosis in the chondrogenic cell line ATDC5. This is associated with a decrease in the expression of PTHrP, which shares the same receptor with PTH, and it is significant that PTHrP rescues these cells from apoptosis. METHODS: Fetuses derived from transgenic mice expressing FGFR3(Ach) under the control of the type II collagen promoter (AchTG) or from wild-type mice were obtained on the 15th day of pregnancy. The femurs were collected from these specimens and cultured for 4 days with PTH. The effects of PTH treatment were then determined by morphometric and histological analyses, in situ hybridization of type X collagen mRNA, and the TUNEL assay. RESULTS: AchTG femurs showed suppressed growth compared with wild type (0.29+/-0.10 mm vs. 0.46+/-0.06 mm, respectively; p<0.05), particularly in cartilage. PTH treatments improved the growth velocity in the femurs of the AchTG (0.50+/-0.06 mm; p<0.01 vs. control). This was associated with the inhibition of both differentiation and apoptosis in chondrocytes. CONCLUSIONS: Our data suggest that PTH inhibits differentiation and apoptosis in chondrocytes and improves bone growth. These effects thus counterbalance the effects of FGFR3 mutations. PTH therefore is a potential therapeutic agent for achondroplasia.

Sustained phosphorylation of mutated FGFR3 is a crucial feature of genetic dwarfism and induces apoptosis in the ATDC5 chondrogenic cell line via PLCgamma-activated STAT1.

The most frequent type of rhizomelic dwarfism, achondroplasia (ACH), is caused by mutations in the fibroblast growth factor receptor 3 (FGFR3) gene. Mutations in FGFR3 result in skeletal dysplasias of variable severity, including mild phenotypic effects in hypochondroplasia (HCH), severe phenotypic effects in thanatophoric dysplasia types I (TDI) and II (TDII), and severe but survivable phenotypic effects in severe achondroplasia with developmental delay and acanthosis nigricans (SADDAN). To explore the molecular mechanisms that result in the different phenotypes, we investigated the kinetics of mutated versions of FGFR3. First, we assayed the phosphorylation states of the mutated FGFR3s and found that the level of phosphorylation in TDI-FGFR3 was lower than in ACH-FGFR3, although the other mutants were phosphorylated according to phenotypic severity. Second, we analyzed the duration of the phosphorylation. TDI-FGFR3 was not highly phosphorylated under ligand-free conditions, but the peak phosphorylation levels of TDI-FGFR3 and ACH-FGFR3 were maintained for 30 min after stimulation with FGF-1. Moreover, ligand-dependent phosphorylation of TDI-FGFR3, but not ACH-FGFR3, lasted for more than 8 h after FGF-1 administration. The other mutant proteins showed sustained phosphorylation independent of ligand presence. Third, we investigated the intracellular localization of the mutant proteins. Immunofluorescence analysis showed accumulations of TDII-FGFR3, SADDAN-FGFR3, and a portion of TDI-FGFR3 in the endoplasmic reticulum (ER). Based on these data, we concluded that sustained phosphorylation of FGFR3 causes chondrodysplasia, and the phenotypic severity depends on the proportion of ER-localized mutant FGFR3. In FGFR3 signaling, the transcription factor, signal transducer and activator of transcription 1 (STAT1) inhibit proliferation and induce apoptosis of chondrocytes. Here we reveal that phospholipase C gamma (PLCgamma) mediates FGFR3-induced STAT1 activation. Both PLCgamma and STAT1 were activated by FGFR3 signaling, but a dominant-negative form of PLCgamma (DN-PLCgamma) remarkably reduced STAT1 phosphorylation. Apoptosis assays revealed that the constitutively active forms of FGFR3 (TDII-FGFR3) and STAT1 (STAT1-C) induce apoptosis of chondrogenic ATDC5 cells via caspase activity. DN-PLCgamma reduced the apoptosis of ATDC5 cells expressing TDII-FGFR3, but over-expression of both DN-PLCgamma and STAT1-C induced apoptosis. Therefore, we conclude that a PLCgamma-STAT1 pathway mediates apoptotic signaling by FGFR3.