Vitamin D-Dependent Rickets, Type I (CYP27B1)
Vitamin D-dependent rickets, type I is a rare autosomal recessive disorder caused by pathogenic variants in CYP27B1. Individuals typically develop symptoms within a few months after birth. Individuals with this disorder may experience bone pain, delayed growth, fractures, bowed legs and widening of metaphyses. Other symptoms include dental abnormalities and secondary hyperparathyroidism. Hypocalcemia (low calcium levels) may also cause muscle weakness and seizures. With treatment, the life expectancy is normal. Pathogenic variants that reduce, but do not eliminate, enzymatic activity result in a milder phenotype. This disorder is found in a higher prevalence in the French Canadian population.
For information about carrier frequency and residual risk, please see the residual risk table.