In young patients with acromegaly/gigantism onset <30 years of age and a sparsely-granulated somatotroph tumor, especially in the presence of a positive family history, an investigation for germline line mutation of the aryl hydrocarbon receptor-interacting protein (AIP), causing familial isolated pituitary adenoma (FIPA), should be considered [37]. The gene discussed is AIP; the disease is familial isolated pituitary adenoma.