• benign telangiectasia
• capillary malformation
• Rendu-Osler-Weber
• linkage
• CMC1

• CM, capillary malformation
• HBT, hereditary benign telangiectasia
• HHT, hereditary haemorrhagic telangiectasia

Telangiectases are characterised by an abnormal permanent dilatation of end vessels—mainly venules but occasionally also capillaries and arterioles—in the subpapillary plexus in the upper part of the dermis.¹ Hereditary benign telangiectasia (HBT; OMIM 187260) is a rare genetic skin disorder classified among the primary or idiopathic telangiectases.¹ Affected individuals present with widespread cutaneous plaque-like, punctate, radiating or arborising telangiectases, which usually appear in early childhood with a random distribution. The young lesions are small and red and tend to increase in size with age, becoming softer and salmon-pink, almost like normal skin.^2,3 Lesions are invariably asymptomatic but can be responsible for mild cosmetic disability. There is no bleeding diathesis or systemic vascular lesions. Thus HBT is considered the benign form of hereditary haemorrhagic telangiectasia (HHT or Rendu-Osler-Weber disease; OMIM 187300 and 600736).⁴ Several familial cases showing autosomal dominant inheritance have been described.^2–3,5–10 However, owing to the small size of these families, no locus has been identified so far.

Capillary malformation (CM or “port wine stain”; OMIM 163000) is a common vascular anomaly occurring in 0.3% of newborns and can be inherited as an autosomal dominant trait with incomplete penetrance and variable expression.^11–13 CM usually presents as a single flat lesion located in the head and neck, typically changing in colour from pink to purple with age.¹¹ In published reports, HBT and CM have often been considered distinct disorders, based on the clinical presentation of cutaneous lesions, but overlapping phenotypes have been described in some families.^8,12 A locus for CM has recently been mapped to a 23-cM region on chromosome 5q13–q15 (CMC1).^12,13 Here we report clinical and histological features of a large HBT family which showed linkage to CMC1.