Refractory Rickets

Nutritional rickets, caused by vitamin D and/or calcium deficiency is by far the most common cause of rickets. In resource-limited settings, it is therefore not uncommon to treat rickets with vitamin D and calcium. If rickets fails to heal and/or if there is a family history of rickets, then refractory rickets should be considered as a differential diagnosis. Chronic low serum phosphate is the pathological hallmark of all forms of rickets as its low concentration in extracellular space leads to the failure of apoptosis of hypertrophic chondrocytes leading to defective mineralisation of the growth plate. Parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23) control serum phosphate concentration by facilitating the excretion of phosphate in the urine through their action on the proximal renal tubules. An increase in PTH, as seen in nutritional rickets and genetic disorders of vitamin D-dependent rickets (VDDRs), leads to chronic low serum phosphate, causing rickets. Genetic conditions leading to an increase in FGF23 concentration cause chronic low serum phosphate concentration and rickets. Genetic conditions and syndromes associated with proximal renal tubulopathies can also lead to chronic low serum phosphate concentration by excess phosphate leak in urine, causing rickets. In this review, authors discuss an approach to the differential diagnosis and management of refractory rickets

Vitamin D Dependent Rickets Type 1A Caused by CYP27B1 Mutation

Vitamin D dependent rickets type 1A (VDDR1A) is an autosomal recessive disorder caused by mutations in CYP27B1 . Clinical findings are growth retardation, hypotonia, muscle weakness, hypocalcemic seizures, and radiological features of rickets. We aimed to present the VDDR1A case with a genetic study of CYP27B1 . The 14-month-old boy was admitted to the hospital due to a seizure. Serum calcium, phosphorus, alkaline phosphatase, parathyroid hormone (PTH), 25(OH) vitamin D, and 1,25(OH)2 vitamin D values were 5.1 mg/dL, 3.7 mg/dL, 705 IU/L, 429 pg/mL, 24.9 ng/mL, and 8.8 pg/mL, respectively. Radiological study showed cupping and fraying of the distal ulna and radius. The molecular genetic study revealed that the patient had a compound heterozygous mutation, Phe443Profs*24 and c.589+1G>A, in CYP27B1 . Genetic analysis of the family members presented that the mother was heterozygous for the mutation c.589+1G>A, and that the father was heterozygous for Phe443Profs*24. The patient was treated with calcium lactate and calcitriol. Until now, six Korean patients with VDDR1A have been studied. Including this case, Korean patients with VDDR1A were found to have only three different mutations in 14 alleles, indicating that the mutation in the CYP27B1 gene is homogeneous in the Korean population.

A Case of Type I Vitamin D-dependent Rickets with Unilateral Aplasia of Kidney

Vitamin D-dependent rickets(VDDR) is a rare autosomal disorder, characterized by hypocalcemia, hypophosphatemia, increased alkaline phosphatase, secondary hyperparathyroidism and many other clinical features. Type I VDDR is due to congenital defects of renal 1alpha-hydroxylase, the enzyme responsible for the conversion of 25-(OH)D3 to 1,25-(OH)2D3. Type II VDDR arise from target organ resistance to 1,25-(OH)2D3. Unilateral renal aplasia is generally thought to result from a lack of induction of the metanephric blastema from the ureteral bud, which may be secondary to ureteral bud maldevelopment and/or to a problem with the formation of the mesonephric duct. The incidence of unilateral renal aplasia is approximately 1/500-3,200. Type 1 VDDR associated with unilateral renal aplasia has not been reported yet. Thus we report a case of a 3 month old female infant diagnosed as type 1 VDDR with unilateral aplasia of kidney.

A Case of Vitamin D-Dependent Rickets, Type 1 / 소아과

"Rickets" is the term applied to impaired mineralization at epiphyseal growth plate, resulting in deformity and impaired linear growth of long bones. Rickets may arise as a result of vitamin D deficiency or abnormality in metabolism. Vitamin D-dependent rickets (VDDR) is rare autosomal recessive disorder in which affected individuals have clinical features of vitamin D deficiency. In 1961, Prader first described this disorder including severe clinical features of rickets, such as hypophosphatemia, hypocalcemia, muscle weakness and seizure. Two distinctive hereditary defects, type I VDDR and type II VDDR have been recognized in vitamin D metabolism. Type I VDDR may be due to congenital defects of renal 1 alpha-hydroxylase, the enzyme responsible for conversion of 25 (OH) D3. These patients have low to detectable 1,25(OH)2D3 in presence of normal to raised 25 (OH) D3. In type II VDDR, renal production of 1,25(OH)2D3 is intact but 1,25(OH)2D3 is not used effectively and target organ resistant to 1,25(OH)2D3 is respectively derived from the abnormality in the vitamin D receptor. We report a case of a 25 month-old girl with typical clinical features of VDDR type I rickets, hypocalcemia, increased alkaline phosphatase and secondary hyperparathyroidism.

Type I Vitamin D Dependent Rickets

PURPOSE: Vitamin D dependent rickets (VDDR) is a rare, autosomal recessively transmitted disorder characterized by hypocalcemia, hypophosphatemia, increased alkaline phosphatase, secondary hyperparathyroidism and many other clinical features. Type l VDDR arises from primary deficiency in the renal 1alpha-hydroxylase that produces 1,25 (OH)2D3. So patients with type I VDDR require life long administration of vitamin D. METHODS: There had been 6 children (4 boys and 2 girls) who were diagnosed as type I VDDR in the Department of Pediatrics, Seoul National University Children's Hospital from March 1983 to May 1997. The medical records, Clinical findings, laboratory, radiologic findings, and response to therapy of these children were analyzed retrospectively. RESULTS: The median age at diagnosis was 19.5 month, and 2 families (33.3%) had family history of rickets. The major presenting symptoms were bowing leg (100%), short stature (100%), and hypocalcemic tetany (67%). Serum levels of 1,25 (OH)2D3 7.0 3.06pg/mL (normal : 20-76pg/mL), respectively. Pretreatment serum levels of calcium (6.9 1.67mg/mL), phosphate (6.9 1.67mg/mL) and alkaline phosphatase (1892 966.4IU/L) were returned to normal levels after treatment (P<0.01). The height standard deviation scores (Z scores) were increased significantly, also (P<0.01). The side effects detected during vitamin D ttherapy were hypercalcemia (33%), hypercalciuria (67%) and nephrocalcinosis (50%). CONCLUSION: This is the first report of type I VDDR in our country. All patients revealed the characteristic clinical, laboratory and radiologic findings, and one third of patients had positive family history. The treatment improved all the clinical, laboratory and radiologic findings significantly including growth. However, complications developed in some patients during the long- term therapy of vitamin D.