The aim of the study was to characterize abnormalities of calcium-phosphate and vitamin D3 metabolism in children with a past history of "mild" Lightwood-type idiopathic infantile hypercalcaemia. Seventeen seemingly healthy children aged 2-12 years, with long-term idiopathic hypercalcaemic syndrome since infancy were studied. Two reference groups were also included (vitamin D3 intoxication/healthy and Williams groups). Despite a long-term milk-restricted diet and a restricted vitamin D3 intake, urinary calcium excretion in the study group was 0.117 +/- 0.07 mumol/kg per 24 h. Compared with the reference groups (0.047 +/- 0.029 and 0.067 +/- 0.06 mumol/kg per 24 h, P < 0.05), there was significant hypercalciuria in the children with idiopathic hypercalcaemia since infancy. Serum concentrations of 25-hydroxyvitamin D3 in the study group were also elevated compared with the reference groups (57.4 +/- 15.5 vs. 34.6 +/- 9.3 and 22.7 +/- 10.5 ng/ml). 1,25-Dihydroxyvitamin D3 levels were at the upper limit of normal (45.9 +/- 13.1 vs. 35.0 +/- 8.1 and 30.0 +/- 13.7 pg/ml). Non-progressive, clinically silent nephrocalcinosis was visible on ultrasound examinations. The disturbances of vitamin D3 and calcium-phosphate metabolism persistent in the normocalcaemic phase of idiopathic infantile hypercalcaemia may be a primary metabolic defect of the condition. The mechanisms leading to elevation of metabolites of 1,25-dihydroxy- and 25-hydroxyvitamin D3 and the relationship between this and persistent hypercalciuria and nephrocalcinosis need pathophysiological explanation.
Dominantly inherited isolated hyperparathyroidism (DIIH) is rare in childhood. It may be the first biochemical abnormality in the multiple endocrine neoplasia type I (MEN I) and type II (MEN II) syndromes. Its clinical course is usually asymptomatic or of low morbidity. Radiographic examination is most often normal. We describe six members of a family with distinctive phenotype and DIIH. Limited systemic symptoms and severe radiographic osteitis fibrosa cystica were further unusual features in this family. The diagnosis of DIIH was made only after a 9-year-old girl developed hypercalcaemic crisis after a pathological femoral fracture. Distinctive phenotype, unusual clinical course and unparalleled radiographic changes suggest a not yet described syndromic association.
On the basis of 3 infants with primary congenital hyperparathyroidism we discuss problems in the early diagnosis and interpretation of the results of laboratory findings. The lack of increased renal echogenicity and hypercalciuria, which is regularly present in idiopathic hypercalcaemia is emphasized. In contrast to secondary hyperparathyroidism caused by prolonged hypocalcaemia, e.g. in patients treated by longterm haemodialysis, the aetiology of primary hyperparathyroidism (pHPT) remained unclear although molecular genetic studies suggest that the development of parathyroid adenoma may be due to gene mutation in a cell. Congenital pHPT is a particularly rare condition usually due to diffuse hyperplasia of all parathyroid glands. Its inheritance is known to be autosomal. Three infants with congenital primary hyperparathyroidism were treated at the Child Health Centre in the years 1987-1988.
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