Vitamin D-dependent rickets (VDDR) type 1A is a rare autosomal recessive disorder caused by cytochrome P450 family 27 subfamily B member 1 (CYP27B1) mutations and can lead to deficiencies in 1α-hydroxylase activity. The present study describes the case of a 39-year-old male patient who presented with rickets and deformities of limbs. Blood biochemical analysis revealed hypocalcemia and high serum parathyroid hormone (PTH) levels. Whole-exome Sanger sequencing using peripheral venous blood of this patient and his parents revealed exon1 c.182T>C, a novel mutation. Through physical examination, laboratory tests, imaging including lower limbs and lumbar spine X-ray and pelvis CT scan, and genetic testing, the patient was diagnosed with VDDR-1A. Following 1 month of treatment with 0.5 µg 1,25-dihydroxy-vitamin D3 twice daily and 0.6 g calcium carbonate once daily, follow-up examinations revealed that the patient's PTH and serum calcium levels had returned to normal. As the patient was diagnosed in his adulthood and missed the optimal treatment period, he developed irreversible deformities. If VDDR-1A can be diagnosed during infancy and childhood, skeletal deformities may be prevented. Therefore, the present report supports the proposal of early genetic sequencing in children with calcium deficiencies for the early diagnosis of rare diseases such as VDDR-1A, -1B and -2A and hereditary hypophosphatemic rickets. Since VDDR-1A diagnosed in adults is rare, the present case may provide clinicians with further insights into the characteristics of this rare disease.
Keywords: cytochrome P450 family 27 subfamily B member 1; deformities; novel mutation; rickets; vitamin D-dependent rickets type 1A.
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