ESPE Abstracts

Introduction: Vitamin D-dependent rickets type 2A (VDDR2A) is a rare autosomal recessive disease that caused by mutations in the vitamin D receptor (VDR) gene. Hypocalcemia, high alkaline phosphatase, secondary hyperparathyroidism, high 1.25-OH vitamin D (1.25-OHD) levels despite normal 25-OH vitamin D (25-OHD) levels are diagnostic. The clinical signs are rickets, short stature, recurrent lung infections and total/subtotal alopecia. Here, we present a case of VDDR2A without alopecia.

Case: A 1.5-year-old male patient was admitted because of inability to walk. It was learned that he was born on term with 3150 gr and there was no consanguinity between his parents. On physical examination, height: 6 cm (-2.07 SDS), weight:10.6 kg (-0.73 SDS), body mass index:18.35 kg/m2 (1.08 SDS), his anterior fontanelle had closed, wide wrists, rachitic rosaries, and he did not have alopecia. The laboratory findings were as followed; calcium: 6.1 mg/dl, phosphorus: 3.5 mg/dl, alkaline phosphatase: 1313 IU/l, parathormone: 454 pg/ml, 25-OHD: 9.45 ng/ml, 1.25-OHD: 23.26 pg/ml, urinary calcium/creatinine: 0.03. Oral calcium lactate 75 mg/kg/day and intravenous calcium gluconate 4x1 ml/kg (elementary calcium 36 mg/kg/g) treatments were started. 150.000IU vitamin D stoss was given. The patient, whose hypocalcemia did not improve despite these treatments, was started 2x0.5µg calcitriol treatment. A diagnosis of VDDR was considered in this case due to long-term treatment-resistant hypocalcemia, need for high-dose calcitriol (3x5 µg), and relatively increased 1.25-OHD compared to 25-OHD. The genetic analysis revealed that C.803T>C (P.Ile268Thr) homozygous in the 8th exon of the VDR gene. Our case had a high calcitriol dose requirement until the age of 3.5 (16.5 µg/day). The patient, who is currently 11 years and 9 months old, has normal anthropometry and normocalcemia and normal urinary calcium/creatinine ratio while receiving 4x7 g calcium lactate (60 mg/kg/g) and calcitriol 3x1 µg (56 ng/kg/g) treatments. However, his BMD score is observed to be shifted towards osteosclerosis.

Results: The phenotype-genotype correlation has been defined in cases with VDDR2A. Although it has been reported that the changes in the ligand binding site have a milder course and generally do not cause alopecia, as in our case, the dose of calcitriol, which provides normocalcemia, was high inconsistently with the mild clinical course. Although alopecia is helpful in the diagnosis in VDDR2A cases, it should be kept in mind that it will not be seen in some cases, and the phenotype-genotype relationship may show case-specific differences in each case.