Abstract

Two rare genetic diseases can cause rickets in children. When 1 alpha hydroxylase is defective, calcitriol can not be synthesized. This disease is known as vitamin D dependent rickets type 1 or as psudovitamin D deficiency rickets. When vitamin D reseptor is defective the disease is known as hereditary vitamin D resistan rickets or as vitamin D dependent rickets type 2. Both diseases are rare autosomal recessive disorders, and characterized with hypocalcemia, elevated parathyroid hormone and alkaline phosphatase levels and similar clinical features as nutritional rickets. The differential diagnosis of these diseases can be made with serum 1,25(OH)2D levels. Patients with type 1 have low levels of 1,25(OH)2D, but patients with type 2 have increased levels of 1,25(OH)2D. In this article, these rare genetic diseases are reported with two cases.