Contributed by: Dr Sunita Bijarnia-Mahay Institute of Medical Genetics and Genomics, Sir Ganga Ram Hospital, New Delhi, India
	Email: Bijarnia@gmail.com
	This child was referred for evaluation of global developmental delay and a chronic skin disorder. Abnormalities noted in the MRI brain images (T2-weighted coronal and sagittal sections) are highlighted with arrows. Identify the condition.
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Answer to PhotoQuiz 63

Vitamin D Dependent Rickets Type 2A (VDDR2A) (OMIM #277440)

Vitamin D dependent rickets type 2A (VDDR2A) is an autosomal recessive disorder caused by biallelic pathogenic variants in the VDR gene (OMIM * 601769). The disorder is characterized by progressive rickets which usually manifests in early childhood with poor growth and skeletal deformities. Alopecia is present in almost two-thirds of affected individuals and is an important diagnostic clue. Biallelic mutations in the VDR (vitamin D receptor) gene reduce the action of the receptor which leads to an impaired intestinal absorption of calcium and phosphate. Biochemical findings include severe hypocalcemia, hypophosphatemia, secondary hyperparathyroidism with high levels of serum alkaline phosphatase, and elevated serum levels of calcitriol (1,25- dihydroxyvitamin D3). Radiological features include severe rachitic changes, osteomalacia, and decreased bone mineralization. Treatment includes daily administration of high doses of oral calcitriol and oral calcium, with intravenous calcium infusions to manage severe hypocalcemia.

Correct responses were given by:

1. Dr Sunita Bijarnia-Mahay, Sir Ganga Ram Hospital, New Delhi 2. Dr Suvarna Ghansham Magar, MGM Medical College, Aurangabad 3. Dr Sheeba Farooqui, Kasturba Medical College, Manipal, Karnataka 4. Dr Surya G Krishnan. Centre for Human Genetics, Bangalore.