FGF23 and Hypophosphatemic Rickets/Osteomalacia.

PURPOSE OF REVIEW: X-linked hypophosphatemia and tumor-induced osteomalacia are diseases characterized by hypophosphatemia with impaired proximal tubular phosphate reabsorption. Complete resection of responsible tumors is the first-line therapy for patients with tumor-induced osteomalacia. In contrast, phosphate and active vitamin D have been used for patients with X-linked hypophosphatemia and inoperable ones with tumor-induced osteomalacia. The purpose of this review is to summarize the pathogenesis of these diseases and discuss about the new treatment. RECENT FINDINGS: Excessive FGF23 production has been shown to underline several kinds of hypophosphatemic rickets/osteomalacia including X-linked hypophosphatemia and tumor-induced osteomalacia. Burosumab, an anti-FGF23 monoclonal antibody, was approved for clinical use, while the indications of burosumab are different depending on countries. The inhibition of excessive FGF23 activity has been approved as a new therapy for several kinds of hypophosphatemic diseases. Further studies are necessary to clarify the long-term effects and safety of burosumab.

A delayed diagnosis of atypical immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome: A case report.

INTRODUCTION: Immune dysregulation, polyendocrinopathy, enteropathy, and X-linked (IPEX) syndrome is a rare monogenic autoimmune disease, which is caused by mutations in the forkhead box protein 3 gene, can affect various systems. The typical clinical manifestations of IPEX are enteropathy, type 1 diabetes mellitus, and skin diseases. However, some atypical phenotypes can easily be misdiagnosed clinically. PATIENT CONCERNS: A 9-year-and-7-month old patient suffered from recurrent wheezing, hematochezia, and eczematous dermatitis at the age of six months, but did not have any manifestations of autoimmune endocrinopathy. The patient was treated with glucocorticoids for more than six years, and he developed bronchiectasis. DIAGNOSIS: Whole exome sequencing revealed a hemizygous pathogenic mutation c.1010G>A, p. (Arg337Gln) in Forkhead box protein 3 gene (NM_014009.3). INTERVENTIONS: The patient was treated with oral mycophenolate mofetil combined with inhaled budesonide formoterol for six months after diagnosis. OUTCOMES: The respiratory symptoms of the patient seemed to be controlled but eczematous dermatitis progressed, which led the patient to give up the treatment. CONCLUSION: Early diagnosis and treatment of IPEX are crucial. Lung injury may be a major problem in the later stages of atypical IPEX, and mycophenolate mofetil seems to control the respiratory symptoms, but could induce significant skin side effects.

Possible COVID-19 reinfection in a patient with X-linked agammaglobulinaemia.

This report highlights the case of a patient with X-linked agammaglobulinaemia (XLA) and resultant bronchiectasis who was discharged from hospital after recovering from real-time reverse transcriptase-PCR positive COVID-19 infection having had a subsequent negative swab and resolution of symptoms, but was readmitted 3 weeks later with recrudescent symptoms and a further positive swab. Although there are reports of COVID-19 infection in XLA, for the first time we report a case of possible reinfection. Lessons learnt from this case include the potential for reinfection of COVID-19 in a patient with a weakened immune system and the importance of repeating COVID-19 swabs in inpatients. Extra caution needs to be taken when providing care in groups of patients who have a weakened or absent immune system.

Clinical and Genetic Profile of X-Linked Agammaglobulinemia: A Multicenter Experience From India.

Background: There is paucity of literature on XLA from developing countries. Herein we report the clinical and molecular profile and outcome in a multicenter cohort of patients with XLA from India. Methods: Data on XLA from all regional centers supported by the Foundation for Primary Immunodeficiency Diseases (FPID), USA and other institutions providing care to patients with PIDs were collated. Diagnosis of XLA was based on European Society for Immunodeficiencies (ESID) criteria. Results: We received clinical details of 195 patients with a provisional diagnosis of XLA from 12 centers. At final analysis, 145 patients were included (137 'definite XLA' and eight 'probable/possible XLA'). Median age at onset of symptoms was 12.0 (6.0, 36.0) months and median age at diagnosis was 60.0 (31.5, 108) months. Pneumonia was the commonest clinical manifestation (82.6%) followed by otitis media (50%) and diarrhea (42%). Arthritis was seen in 26% patients while 23% patients developed meningitis. Bronchiectasis was seen in 10% and encephalitis (likely viral) in 4.8% patients. Pseudomonas aeruginosa was the commonest bacterial pathogen identified followed by Streptococcus pneumoniae, Staphylococcus aureus and Klebsiella pneumoniae. Molecular analysis revealed 86 variants in 105 unrelated cases. Missense variants in BTK gene were the most common (36%) followed by frameshift (22%) and nonsense variants (21%). Most pathogenic gene variants (53%) were clustered in the distal part of gene encompassing exons 14-19 encoding for the tyrosine kinase domain. Follow-up details were available for 108 patients. Of these, 12% had died till the time of this analysis. The 5-year and 10-year survival was 89.9% and 86.9% respectively. Median duration of follow-up was 61 months and total duration of follow-up was 6083.2 patient-months. All patients received intravenous immunoglobulin (IVIg) replacement therapy. However, in many patients IVIg could not be given at recommended doses or intervals due to difficulties in accessing this therapy because of financial reasons and lack of universal health insurance in India. Hematopoietic stem cell transplant was carried out in four (2.8%) patients. Conclusion: There was a significant delay in the diagnosis and facilities for molecular diagnosis were not available at many centers. Optimal immunoglobulin replacement is still a challenge.

Treatment with rapamycin can restore regulatory T-cell function in IPEX patients.

BACKGROUND: Immune-dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a lethal disease caused by mutations in a transcription factor critical for the function of thymus-derived regulatory T (Treg) cells (ie, FOXP3), resulting in impaired Treg function and autoimmunity. At present, hematopoietic stem cell transplantation is the therapy of choice for patients with IPEX syndrome. If not available, multiple immunosuppressive regimens have been used with poor disease-free survival at long-term follow-up. Rapamycin has been shown to suppress peripheral T cells while sparing Treg cells expressing wild-type FOXP3, thereby proving beneficial in the clinical setting of immune dysregulation. However, the mechanisms of immunosuppression selective to Treg cells in patients with IPEX syndrome are unclear. OBJECTIVE: We sought to determine the cellular and molecular basis of the clinical benefit observed under rapamycin treatment in 6 patients with IPEX syndrome with different FOXP3 mutations. METHODS: Phenotype and function of FOXP3-mutated Treg cells from rapamycin-treated patients with IPEX syndrome were tested by flow cytometry and in vitro suppression assays, and the gene expression profile of rapamycin-conditioned Treg cells by droplet-digital PCR. RESULTS: Clinical and histologic improvements in patients correlated with partially restored Treg function, independent of FOXP3 expression or Treg frequency. Expression of TNF-receptor-superfamily-member 18 (TNFRSF18, glucocorticoid-induced TNF-receptor-related) and EBV-induced-3 (EBI3, an IL-35 subunit) in patients' Treg cells increased during treatment as compared with that of Treg cells from untreated healthy subjects. Furthermore inhibition of glucocorticoid-induced TNF-receptor-related and Ebi3 partially reverted in vitro suppression by in vivo rapamycin-conditioned Treg cells. CONCLUSIONS: Rapamycin is able to affect Treg suppressive function via a FOXP3-independent mechanism, thus sustaining the clinical improvement observed in patients with IPEX syndrome under rapamycin treatment.

CHILD syndrome: successful treatment of skin lesions with topical lovastatin and cholesterol lotion.

CHILD syndrome (Congenital Hemidysplasia, Ichthyosiform erythroderma, Limb Defects) is a rare X-linked dominant disease. The authors report a 2-month-old patient presenting with typical features of CHILD syndrome that was treated with a topical solution containing cholesterol and lovastatin, with complete clearance of her CHILD nevus. The changes in skin lipid metabolism that explain the CHILD ichthyosiform nevus and their correction through topical application of cholesterol and lovastatin are discussed.

Kawasaki disease and immunodeficiencies in children: case reports and literature review.

Kawasaki disease (KD) has features that appear supporting an infectious cause with a secondary deranged inflammatory/autoimmune response. The association of KD in adults with human immunodeficiency virus infection and the presence of KD in patients with immunodeficiency disorders support the infectious theory. We present four KD patients associated with immunodeficiencies: one with X-linked agammaglobulinemia, one with HIV infection, and two with leukemia; one of these patients also had Down syndrome. We did a literature search to find out all reported cases of immunodeficiency with KD in children. In immunodeficiency disorders, the inability of the immune system to eradicate the pathogens coupled to an exaggerated inflammatory response, especially in chronic granulomatous disease, may lead to the development of KD. The study of patients with immunodeficiencies complicated with KD may shed light into the etiopathogenesis of the disease.

Btk Inhibitors as First Oral Atherothrombosis-Selective Antiplatelet Drugs?

Bruton's tyrosine kinase (Btk) is essential for B cell differentiation and proliferation, but also platelets express Btk. Patients with X-linked agammaglobulinemia due to hereditary Btk deficiency do not show bleeding, but a mild bleeding tendency is observed in high dose therapy of B-cell malignancies with ibrutinib and novel second-generation irreversible Btk inhibitors (acalabrutinib and ONO/GS-4059). This review discusses recent studies that may explain this apparent paradox and gives mechanistic insights that suggest a unique potential of low dose irreversible Btk inhibitors as atherothrombosis-focused antiplatelet drugs.

CHILD syndrome: successful treatment of skin lesions with topical lovastatin and cholesterol lotion

Abstract: CHILD syndrome (Congenital Hemidysplasia, Ichthyosiform erythroderma, Limb Defects) is a rare X-linked dominant disease. The authors report a 2-month-old patient presenting with typical features of CHILD syndrome that was treated with a topical solution containing cholesterol and lovastatin, with complete clearance of her CHILD nevus. The changes in skin lipid metabolism that explain the CHILD ichthyosiform nevus and their correction through topical application of cholesterol and lovastatin are discussed.

Vedolizumab treatment in a patient with X-linked agammaglobulinemia, is it safe and efficient?

Çekiç S, Özgür T, Karali Y, Özkan T, Kiliç SS. Vedolizumab treatment in a patient with X-linked agammaglobulinemia, is it safe and efficient? Turk J Pediatr 2019; 61: 937-940. The loss of inflammatory regulation resulting from the absence of B-lymphocytes leads to a risk for autoimmune and autoinflammatory complications. There is no data on the use of Vedolizumab in patients with X-linked agammaglobulinemia (XLA) as well as children with another primary immunodeficiency (PID) diseases. A 4-year-old boy was admitted to our clinic with a history of recurrent respiratory tract infections. He was diagnosed with XLA based on extremely low immunoglobulins, very low level of B cells, genetic mutation of BTK gene, and family history. At the age of 8, he suffered from intermittent fever attacks, abdominal pain, weakness, oral aft, and weight loss. His clinical and laboratory features were consistent with inflammatory bowel disease. Histopathological examination of the biopsy material obtained from terminal ileum, colon and cecum showed Crohn`s disease. Initially, he was treated with prednisolone and infliximab. Because of the lack of response, infliximab treatment was switched to adalimumab. Terminal ileum was resected to relieve obstruction complication. Although he had been treated with adalimumab, a significant improvement was not observed. Vedolizumab (Entyvio™), a humanized monoclonal antibody α4ß7 integrin-receptor antagonist, was commenced. After treatment with vedolizumab, his fever and abdominal pain attacks reduced, his total daily calorie intake increased and weight gain improved. He began to walk again and continued his school education properly. No side effects were observed in 18 months. This is the first immunocompromised child treated with vedolizumab. The symptoms of the patient receded and no side effect were seen during the treatment.

Long-Term Efficacy and Safety of Hizentra® in Patients with Primary Immunodeficiency in Japan, Europe, and the United States: a Review of 7 Phase 3 Trials.

Many patients with primary immunodeficiency (PID) require immunoglobulin G (IgG) replacement therapy, delivered as intravenous IgG (IVIG) or subcutaneous IgG (SCIG). We aim to identify trends in efficacy and safety that would not be evident in individual studies of small patient numbers. Seven open-label, Phase 3, prospective, multicenter studies of the efficacy and safety of Hizentra® (a SCIG), conducted in Japan, Europe, and the US were summarized. Overall, 125 unique patients received 15,013 weekly infusions during a total observation period of 250.9 patient-years. Mean weekly doses of Hizentra® were 83.22-221.3 mg/kg body weight; infusion rates per patient (total body rate) were 25.2-49.3 mL/h across studies. The rates of infections and serious bacterial infections were 3.10 and 0.03 events per patient/year, respectively. Annualized rates of days hospitalized due to infection, out of work/school, and prophylactic antibiotic use were 0.95, 5.14, and 36.78 per patient, respectively. For the equivalent monthly dose, weekly Hizentra® SCIG administration resulted in expectedly-increased serum IgG trough levels in patients switching from IVIG, and maintained levels in patients switching from previous SCIG. Adverse events (AEs) totaled 5039 (events/infusion 0.094-0.773), almost all of which were mild/moderate. Three thousand one hundred ninety-seven were considered treatment-related, the most common of which were injection site reactions (2919 events; 0.001-0.592 AEs per infusion). Systemic AEs were very uncommon. The results from these seven studies indicate that Hizentra® therapy was both efficacious and well tolerated during long-term treatment. This is particularly important in patients with PID, who may require lifelong IgG replacement therapy.

Anterior, frontal congenital triangular alopecia, redundancy in therapy without improvement.

Congenital triangular alopecia (CTA) is a benign noncicatricial localized pattern of hair loss with unknown etiology. Although referred to as "congenital," CTA may develop in adulthood. It is believed that many cases of CTA are never diagnosed or are misdiagnosed; causing the incidence to be underestimated. The present study evaluates a case of 20-year-old woman presenting with a single circular to oval area of hair-loss in the mid-frontal region of her scalp. To date, about 170 cases of CTA have been reported and we present the first case in which the alopecic patch is located in the mid-frontal region of the scalp. We present this case not only to challenge the preconceived notion that all CTAs are frontotemporal, but also to inform other practitioners about this rare condition and prevent redundant medical treatment.

Inhibition of Btk by Btk-specific concentrations of ibrutinib and acalabrutinib delays but does not block platelet aggregation mediated by glycoprotein VI.

Ibrutinib and acalabrutinib are irreversible inhibitors of Bruton tyrosine kinase used in the treatment of B-cell malignancies. They bind irreversibly to cysteine 481 of Bruton tyrosine kinase, blocking autophosphorylation on tyrosine 223 and phosphorylation of downstream substrates including phospholipase C-γ2. In the present study, we demonstrate that concentrations of ibrutinib and acalabrutinib that block Bruton tyrosine kinase activity, as shown by loss of phosphorylation at tyrosine 223 and phospholipase C-γ2, delay but do not block aggregation in response to a maximally-effective concentration of collagen-related peptide or collagen. In contrast, 10- to 20-fold higher concentrations of ibrutinib or acalabrutinib block platelet aggregation in response to glycoprotein VI agonists. Ex vivo studies on patients treated with ibrutinib, but not acalabrutinib, showed a reduction of platelet aggregation in response to collagen-related peptide indicating that the clinical dose of ibrutinib but not acalabrutinib is supramaximal for Bruton tyrosine kinase blockade. Unexpectedly, low concentrations of ibrutinib inhibited aggregation in response to collagen-related peptide in patients deficient in Bruton tyrosine kinase. The increased bleeding seen with ibrutinib over acalabrutinib is due to off-target actions of ibrutinib that occur because of unfavorable pharmacodynamics.

Amyloid clearance defect in ApoE4 astrocytes is reversed by epigenetic correction of endosomal pH.

Endosomes have emerged as a central hub and pathogenic driver of Alzheimer's disease (AD). The earliest brain cytopathology in neurodegeneration, occurring decades before amyloid plaques and cognitive decline, is an expansion in the size and number of endosomal compartments. The strongest genetic risk factor for sporadic AD is the ε4 allele of Apolipoprotein E (ApoE4). Previous studies have shown that ApoE4 potentiates presymptomatic endosomal dysfunction and defective endocytic clearance of amyloid beta (Aß), although how these two pathways are linked at a cellular and mechanistic level has been unclear. Here, we show that aberrant endosomal acidification in ApoE4 astrocytes traps the low-density lipoprotein receptor-related protein (LRP1) within intracellular compartments, leading to loss of surface expression and Aß clearance. Pathological endosome acidification is caused by ε4 risk allele-selective down-regulation of the Na+/H+ exchanger isoform NHE6, which functions as a critical leak pathway for endosomal protons. In vivo, the NHE6 knockout (NHE6KO) mouse model showed elevated Aß in the brain, consistent with a causal effect. Increased nuclear translocation of histone deacetylase 4 (HDAC4) in ApoE4 astrocytes, compared with the nonpathogenic ApoE3 allele, suggested a mechanistic basis for transcriptional down-regulation of NHE6. HDAC inhibitors that restored NHE6 expression normalized ApoE4-specific defects in endosomal pH, LRP1 trafficking, and amyloid clearance. Thus, NHE6 is a downstream effector of ApoE4 and emerges as a promising therapeutic target in AD. These observations have prognostic implications for patients who have Christianson syndrome with loss of function mutations in NHE6 and exhibit prominent glial pathology and progressive hallmarks of neurodegeneration.

Burosumab Therapy in Children with X-Linked Hypophosphatemia.

BACKGROUND: X-linked hypophosphatemia is characterized by increased secretion of fibroblast growth factor 23 (FGF-23), which leads to hypophosphatemia and consequently rickets, osteomalacia, and skeletal deformities. We investigated burosumab, a monoclonal antibody that targets FGF-23, in patients with X-linked hypophosphatemia. METHODS: In an open-label, phase 2 trial, we randomly assigned 52 children with X-linked hypophosphatemia, in a 1:1 ratio, to receive subcutaneous burosumab either every 2 weeks or every 4 weeks; the dose was adjusted to achieve a serum phosphorus level at the low end of the normal range. The primary end point was the change from baseline to weeks 40 and 64 in the Thacher rickets severity total score (ranging from 0 to 10, with higher scores indicating greater disease severity). In addition, the Radiographic Global Impression of Change was used to evaluate rachitic changes from baseline to week 40 and to week 64. Additional end points were changes in pharmacodynamic markers, linear growth, physical ability, and patient-reported outcomes and the incidence of adverse events. RESULTS: The mean Thacher rickets severity total score decreased from 1.9 at baseline to 0.8 at week 40 with every-2-week dosing and from 1.7 at baseline to 1.1 at week 40 with every-4-week dosing (P<0.001 for both comparisons); these improvements persisted at week 64. The mean serum phosphorus level increased after the first dose in both groups, and more than half the patients in both groups had levels within the normal range (3.2 to 6.1 mg per deciliter [1.0 to 2.0 mmol per liter]) by week 6. Stable serum phosphorus levels were maintained through week 64 with every-2-week dosing. Renal tubular phosphate reabsorption increased from baseline in both groups, with an overall mean increase of 0.98 mg per deciliter (0.32 mmol per liter). The mean dose of burosumab at week 40 was 0.98 mg per kilogram of body weight with every-2-week dosing and 1.50 mg per kilogram with every-4-week dosing. Across both groups, the mean serum alkaline phosphatase level decreased from 459 U per liter at baseline to 369 U per liter at week 64. The mean standing-height z score increased in both groups, with greater improvement seen at all time points with every-2-week dosing (an increase from baseline of 0.19 at week 64) than with every-4-week dosing (an increase from baseline of 0.12 at week 64). Physical ability improved and pain decreased. Nearly all the adverse events were mild or moderate in severity. CONCLUSIONS: In children with X-linked hypophosphatemia, treatment with burosumab improved renal tubular phosphate reabsorption, serum phosphorus levels, linear growth, and physical function and reduced pain and the severity of rickets. (Funded by Ultragenyx Pharmaceutical and Kyowa Hakko Kirin; ClinicalTrials.gov number, NCT02163577 ; EudraCT number, 2014-000406-35 ).

STRUCTURAL AND FUNCTIONAL MONITORING OF EXTRAMACULAR CYSTOID SPACES IN A CASE OF X-LINKED RETINOSCHISIS TREATED WITH ACETAZOLAMIDE.

BACKGROUND: Carbonic anhydrase inhibitors (CAIs) have been shown to have a beneficial effect on cystoid macular edema in X-linked retinoschisis (XLRS) and other inherited retinal conditions. The effect of CAIs outside the macula has been less well studied. METHODS: Snellen visual acuity, spectral-domain optical coherence tomography (SD-OCT), kinetic visual field, and dark-adapted single-flash full-field electroretinogram (ERG) testing were all done at baseline and at least one follow-up visit. A 55-year-old male diagnosed with XLRS exhibited extensive macular and extramacular cystoid splitting in the right eye and was treated with oral extended-release acetazolamide 500 mg/day. RESULTS: By 6 months of follow-up on acetazolamide treatment, SD-OCT demonstrated resolution of cystoid spaces both within the macula and out to the midperiphery. Visual acuity improved from 20/70 to 20/30. The full-field ERG was distinctly electronegative at both baseline and at a follow-up visit, with oscillatory potentials becoming more apparent at the follow-up visit. Peripheral visual field boundaries did not change significantly. CONCLUSION: This report demonstrates structural resolution of cystoid spaces throughout much of the retina in a patient with XLRS, adding to a published case report in which we first noted that extramacular cystoid spaces observed in XLRS may respond to CAI treatment. To our knowledge, this is the first reported study of follow-up functional studies (ERG and perimetry) in a CAI treatment responder with XLRS.

Helicobacter bilis-Associated Suppurative Cholangitis in a Patient with X-Linked Agammaglobulinemia.

ᅟ: Helicobacter bilis is a commensal bacterium causing chronic hepatitis and colitis in mice. In humans, enterohepatic Helicobacter spp. are associated with chronic hepatobiliary diseases. PURPOSE: We aimed at understanding the microbial etiology in a patient with X-linked agammaglobulinemia presenting with suppurative cholangitis. METHODS: 16S rDNA PCR directly performed on a liver biopsy retrieved DNA of H. bilis. RESULTS: Clinical outcome resulted in the normalization of clinical and biological parameters under antibiotic treatment by a combination of ceftriaxone, metronidazole, and doxycyclin followed by a 2-week treatment with moxifloxacin and a 2-month treatment with azithromycin. CONCLUSION: In conclusion, these data suggest a specific clinical and microbiological approach in patients with humoral deficiency in order to detect H. bilis hepatobiliary diseases.

X-linked Sideroblastic Anemia in a Malay Boy With ALAS2 S568G Mutation.

Dimorphism in peripheral blood film was noted in a 16 year old Malay boy with anemia who was eventually diagnosed with X-linked sideroblastic anemia. A mutation in ALAS2 S568G was identified which has not been described previously in a Malay ethnic group.