An unusual cause of Cushing's syndrome: primary pigmented nodular adrenal dysplasia

We report a case of Cushing's syndrome due to primary pigmented nodular adrenal dysplasia (PPNAD) and discuss the diagnostic process and management of this rare case. The diagnosis of PPNAD is discussed in the context of other causes of Cushing's syndrome. Eighty-five per cent of cases of Cushing's syndrome are due to a pituitary corticotrophic tumour (Cushing's disease). Rarer causes include cortisol secreting adrenal adenoma and ectopic ACTH secretion. In the routine investigation of Cushing's disease it is not unusual to find bilateral adrenal nodules on the CT scan. We present a case of Cushing's syndrome in which this radiographic finding was present and yet the biochemical diagnosis was one of ACTH independent disease. Histology revealed PPNAD.