HEREDITARY HEMORRHAGIC TELANGIECTASIA
By Gary M. White, MD
Patients with hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu disease, develop multiple cutaneous telangiectasias as well as vascular malformations internally.
- The inheritance is autosomal dominant with incomplete penetrance.
- Mutations in one of two chromosomal sites can cause HHT. In HHT1, mutations at chromosome 9 alter the protein endoglin. In HHT2, mutations at chromosome 12 alter the protein ALK1 (activin receptor-like kinase 1). Both ALK1 and endoglin are receptors for transforming growth factor-beta (TGF-beta) and are expressed primarily in arterial endothelial cells. Endoglin, ALK1, as well as other TGF-beta signaling components, are essential during angiogenesis.
Patients present initially with epistaxis in childhood. Later, telangiectatic mats develop on the tongue, lips, fingertips, and elsewhere. Vascular abnormalities of other organs occur including the liver (portal hypertension), spleen, lung (pulmonary arteriovenous malformations, hemoptysis), gastrointestinal tract (GI bleeding, anemia), and urinary tract (hematuria). CNS abscesses may occur presumably from pulmonary arteriovenous malformations which do not filter venous septic foci.
Many complications involving the brain, liver, and lung can develop. Thus, a multidisciplinary approach to therapy is needed with the primary risks being outside of the dermatologist's arena. The cutaneous telangiectasias may be treated with laser. Genetic counseling should be done.
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