CONGENITAL RICKETS Study of the Evolution of Secondary Hyperparathyroidism

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Abstract
A case of congenital rickets of nutritional origin is described in a light-for-date premature infant (gestational age 34 weeks, birthweight 1100 g). X-rays of the long bones showed spread, frayed and cupped metaphyses at birth and at the age of 16 days. Serum calcium was 8.2 mg/100 ml, phosphorus 3.4 mg/100 ml and alkaline phosphatase (A.P.): 323 IU/ml (N≤200) at the age of 3 days. Very high level of serum immunoreactive parathyroid hormone (iPTH) was found at the age of 16 days=295 μlEq/ml (N≤50). Evidence of maternal vitamin D deficiency was demonstrated by low plasma 25-hydroxycholecalciferol (25-OH-CC): 1.0 ng/ml (N: 13.2±4.2) soon after delivery; it was found to be normal (10.2 ng/ml) six months later. Ca infusion (15 mg/kg/3 h) resulted in a marked fall of serum iPTH (280 to 84 μlEq/ml). Administration of vitamin D2 (2400 IU/day for 10 days) induced some healing of the metaphyses; A. P. remained elevated (400 IU/ml); plasma 25-OH-CC was normal 10.2 ng/ml and serum iPTH was 115 μlEq/ml. When 25-OH-CC was given orally for ten days (15 μg/day), plasma 25-OH-CC rose to 64.5 ng/ml with a minor change of serum iPTH (94 μlEq/ml); X-rays of the bones showed osteoporosis. These results suggest a reduced conversion of 25-OH-CC into 1–25-(OH)2-CC.