Hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu) is inherited in which pattern?

• A. X-linked recessive
• B. Autosomal recessive
• C. Mitochondrial
• D. Autosomal dominant

Answer: (D)

Hereditary hemorrhagic telangiectasia is inherited in an autosomal dominant pattern. This disease is caused by germline mutations in genes that encode components of the TGF-β signaling pathway in vascular endothelium (such as ENG, ACVRL1, and SMAD4). A single mutated allele is enough to disrupt normal vessel formation, leading to mucocutaneous telangiectasias and arteriovenous malformations. Because it is autosomal dominant, affected individuals typically have an affected parent, and each child has about a 50% chance of inheriting the condition, with the same risk in males and females. It is not X-linked or mitochondrial, which would show different transmission patterns. Cases can arise from de novo mutations, and expressivity can be variable, so the severity and age of onset can differ among individuals.