Macrogenitosomia praecox due to an interstitial cell tumour of the testis.

An interstitial cell tumour of the testis produces a characteristic clinical picture. Starting between the ages of 2 and 6 years, the boy develops macrogenitosomia praecox with a raised excretion of urinary 17-ketosteroids. The tumour, which is usually unilateral and non-malignant, may not be obvious initially. Occasionally there is gynaecomastia. Penile erections are frequent. The behaviour ranges from normality, through increased aggressiveness, to embarrassing sexual precocity. The differential diagnosis is from virilizing adrenal hyperplasia. 39 cases have been reported (Johnstone, 1967). The following case was treated as one of adrenal virilism for a year before the correct diagnosis was made.