A course of leprechaunism is described in a 6-month-old girl who died of cachexia in the presence of generalized cytomegalia and myocardial metabolic derangement caused by cardiac arterial calcinosis. Proband sib aged 7 suffered from deaf-mutism and imbecility. There were multiple deformities of the face and body, skin hyperkeratosis with papillomatosis and melanoderma, hirsutism, pseudohermaphroditism, breast hyperplasia, normal serum glucose. Ovarian polycystosis and nephromegaly were detected at autopsy. Histologically, there appeared nesidioblastosis, Leydig's cells focal hyperplasia in the ovaries, cystic renal dysplasia calcinosis of cardiac arteries, those of mesentery of the small intestine, spleen, pancreas and thyroid gland. The final diagnosis was established on the basis of the whole complex of clinical and morphological signs.