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 macro-genitosomia 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 gynae-comastia. 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 (John-stone, 1967). The following case was treated as one of adrenal virilism for a year before the correct diagnosis was made. Case Report This boy was born in 1949 weighing 3-3 kg. His voice had always been deep since beginning to talk. He was of a muscular type. Rapid genital develop-ment was noticed at 2 years, but advice was not sought until the age of 41 years. Over the previous year there had been penile erections and possibly emissions. Examination showed an abnormally muscular looking boy, height 118 cm., span width 116 cm. Pubic hair present. Length of penis 8-7 cm. and circumference 8 cm. Both testes felt normal for his age. Bone age 11 years. With a urinary output of 500-600 ml. per day the 17-ketosteroid excretion ranged between 3 6 mg. and 5 6 mg./24 hr. Serum Na was 138 mEq/l., K 4- 4 mEq/l., and Cl 94 mEq/l. A diagnosis of adrenal virilism was made. Treat-ment was started with oral cortisone 25 mg. daily. Over the next year his parents thought he improved in that he 'looked younger'. No regression, however, occurred in the secondary sex characteristics (Fig. 1), in the urinary 17-ketosteroid excretion (Fig. 2), or in the skeletal maturation (Fig. 3). At no time was his behaviour abnormal. Fifteen months later, at the age of 6 years, he had 2 nocturnal emissions within a period of 6 weeks, and this led to reassessment. The right testis was now