Background: Vitamin D dependent type 1 rickets is a rare, autosomal-dominantly inherited disorder due to an inactivating mutation in CYP27B1 (25-OH vitamin D-1-α-hydroxylase) gene. It is characterized by early onset of rickets with hypocalcemia. We report a boy admitted with symptoms of hypocalcemia and who carried a novel mutation in CYP27B1 gene.
Case: The patient was admitted with tetany at the age of 12 months. When he had his first convulsion, he was 9 months old. He did not have prophylaxis of vitamin D and hypocalcemia was detected in his country. Vitamin D was administered orally. Carbamazepine was added for the treatment of seizures and pancrelipase for the treatment of repeated diarrhea episodes. He was born from a consangious marriage. He had one healthy sister and one brother died at the age of 12 months because of hypocalcemia and pneumonia. At physical examination, he had carpopedal spasm. Height, weight and head circumference SDS were −1.83, −1.02, 1.64 respectively. He had caput quadratum and enlargement of wrist. His serum calcium, phosphorus, alkaline phosphatase levels were 5.9 mg/dl, 3.5 mg/dl and 987 IU/l respectively. No abnormalities of acidbase metabolism or renal function were detected. Renal ultrasound revealed nephrocalcinosis (grade 1). Radiological findings included metaphyseal fraying and cupping in wrists. Serum levels of parathormone and 25-OH vitamin D levels were high; 1, 25 OH vitamin D level was low; urine calcium/creatinine ratio was 0.006. Calcium carbonate and calcitriol were administered orally. In follow-up, his liver enzyme levels increased, it was releated to Cytomegalovirus infection. With normal electroencephalography findings and without diarrhea, treatments of carbamazepine and pancrelipase were withdrawen. Serum levels of calcium were normal under treatment of calcitriol and calcium-carbonate. DNA sequencing revealed a novel homozygous mutation of p.Q135X (c.403 C>T) in CYP27B1 gene.
Conclusion: Vitamin D dependent rickets tip 1 is a rare disorder but must be considered even in countries where vitamin D deficiency is still common.
18 Sep 2014 - 20 Sep 2014