Vitamin D dependent rickets, diagnostic and therapeutic difficulties: two case reports.

There are two types of vitamin D dependent rickets (VDDR) that cause rickets in children. Vitamin D dependent rickets type 1 (VDDR-I) is caused by an inborn error of vitamin D metabolism, which interferes with renal conversion of calcidiol (25OHD) to calcitriol (1,25(OH)2D) by the enzyme 1alpha-hydroxylase. Vitamin D dependent rickets type 2 (VDDR-II) is caused by a defect in the vitamin D receptor (VDR). We report cases of two African children affected by VDDR-I and VDDR-II, respectively. Establishing an early diagnosis of these genetic forms of rickets is challenging, especially in developing countries where nutritional rickets (NR) is the most common variety of the disease. A prompt diagnosis is necessary to initiate adequate treatment, resolve biochemical features and prevent complications, such as severe deformities that may require surgical intervention.