text: Familial isolated pituitary adenoma Familial isolated pituitary adenoma (FIPA) is a term that is used to identify a condition that displays an autosomal dominant inheritance and is characterised by the presence of two or more related patients affected by adenomas of the pituitary gland only, with no other associated symptoms that occur in multiple endocrine neoplasia type 1 (MEN-1), Carney complex and with mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene. FIPA was first described in a limited cohort of families by Albert Beckers group in Liège, Belgium; later FIPA was fully characterized in a multicenter international study of 64 families.  FIPA families are divided into those that are homogenous and have the same type of pituitary adenoma in all the affected family members (e.g. only acromegaly, only prolactinoma, etc.), while heterogeneous FIPA families can have different pituitary adenomas in affected family members.
  Genetics of FIPA
  FIPA has two known genetic causes, mutations in the AH receptor-interacting protein (AIP) gene and duplications in chromosome Xq26.3 that include the GPR101 gene that also causes X-linked acrogigantism (X-LAG) syndrome.  About 15–20% of FIPA families carry a germline AIP gene mutation or deletion, and the disease occurs as autosomal dominant with incomplete penetrance, meaning that about 20% of AIP mutation carriers will develop a pituitary adenoma.  AIP mutation associated pituitary adenomas (either presenting as FIPA or as individual, non familial cases) are usually growth hormone-secreting (acromegaly) or prolactin-secreting (prolactinoma) adenomas that are large (macroadenomas) and often occur in children, adolescents and young adults.  Daly and colleagues showed that acromegaly cases with AIP mutations occurred about 20 years before acromegaly cases without AIP mutations and these tumors are large and relatively treatment-resistant.  Due to their young age at onset, AIP mutations are the most frequent genetic cause of pituitary gigantism (29% of cases).