Pseudo-vitamin D deficiency rickets (PDR) and relative hypoparathyroidism: a report of a family.

Abstract

Three siblings with hypocalcemia, variable serum phosphate and elevated serum alkaline phosphatase levels, who are considered to have pseudo-vitamin D deficiency rickets (PDR), are described. In one patient metabolic balance studies were performed during acid loading with ammonium chloride (18 g in 4 days) and dihydrotachysterol (5 mg per day for 4 days) administration. During the acid loading period, fecal calcium excretion increased and was carried over into the dihydrotachysterol administration period resulting in a negative calcium balance, thus indicating defective calcium absorption. Acid loading with ammonium chloride in this patient and in one of his siblings demonstrated an impairment in the acidification of the urine. In one patient the increase in urinary titrable acids (T.A.) was mainly by increased excretion of organic acid. Serum parathyroid levels in two of the subjects were within normal limits in the presence of hypocalcemia, a finding which may indicate relative hypoparathyroidism. The relationship between the role of kidney, parathyroid glands and vitamin D metabolism is discussed and an attempt is made to implicate these factors in the causation of this condition.