Hyperphosphatemic Tumoral Calcinosis

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Abstract
Seven siblings with hyperphosphatemic tumoral calcinosis were studied using metabolic measures. Serum P and 1,25-dihydroxycholecalciferol concentrations were significantly increased and serum parathyroid hormone and 25-hyroxycholecalciferol concentrations were significantly decreased in these subjects. Metabolic balance studies done in 3 of the siblings showed positive Ca and P balances, reflected by increased gastrointestinal absorption and decreased renal excretion. A hereditary abnormality of vitamin D metabolism may be present in patients with hyperphosphatemic tumoral calcinosis. Failure of the normal feedback mechanism regulating the 25-hydroxy-1-.alpha.-hydroxylase enzyme is suggested as the major cause. Although this defect could lead to many of the metabolic abnormalities seen in these patients, the overall contribution of altered vitamin D metabolism to the pathogenesis of tumoral calcinosis is not fully understood.