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Genetic basis of bilateral macronodular hyperplasia
Summary
Bilateral macronodular hyperplasia (BMAH) is often genetic, not ACTH-independent. Mutations in the ARMC5 gene are linked to this condition, which can cause Cushing syndrome.
Area of Science:
- Endocrinology
- Genetics
- Molecular Biology
Background:
- Bilateral macronodular hyperplasia (BMAH), previously termed ACTH-independent macronodular hyperplasia (AIMH), is a condition characterized by adrenal hyperplasia.
- It can lead to Cushing syndrome or subclinical hypercortisolism.
Observation:
- Recent studies indicate that hyperplastic adrenal tissue in BMAH can ectopically produce ACTH, challenging the 'ACTH-independent' classification.
- While historically considered sporadic, a significant genetic component is now recognized in most BMAH cases.
Findings:
- Mutations in the ARMC5 gene, a potential tumor suppressor, are frequently identified in familial BMAH cases and are implicated as the primary cause.
- The inefficient cortisol production by these hyperplastic nodules necessitates the development of large nodules to manifest clinically.
- Clinical symptoms typically emerge later in life, often in the fifth to sixth decades.
Implications:
- BMAH is an underdiagnosed genetic disorder with implications for endocrine health.
- Screening for BMAH and its genetic underpinnings is recommended for affected individuals and their at-risk family members.
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