Spurred by recent developments in molecular neurobiology, the 1990s have seen a burgeoning of interest in the genetic aspects of cerebrovascular diseases. Many types of cerebrovascular lesions are associated with well-defined, genetically determined conditions: cerebral aneurysms accompany polycystic kidney disease; cerebral arteriovenous malformations (AVM) are a major component of hereditary haemorrhagic telangiectasia (HHT, Rendu–Osler–Weber disease); and cerebral cavernous angiomas are associated with at least two genetic mutations (Lozano & Leblanc, 1992; Putnam et al., 1996; Gunel et al., 1995). In this context the elaboration of a new neurocutaneous syndrome, hereditary neurocutaneous angiomatosis (HNA), a condition characterized by the presence of vascular lesions of the skin and brain, is of interest because its molecular characterization may shed light on the etiology of common sporadic cerebrovascular lesions such as AVMs and developmental venous anomalies (DVA) with which it is associated (Zaremba et al., 1979; Hurst & Baraitser, 1988; Leblanc et al., 1996). Most AVMs and DVA are sporadic lesions without associated cutaneous anomalies.
The clinical manifestations of the vascular nevi in HNA depend on their size and location. The lesions, including cavernous angiomas, AVMs, and venous malformations, are multiple and they can range from a few millimetres in apparent diameter to up to 1–2 cm. The color of the lesions depends on their depth, the deeper ones appearing as a flat bluish discoloration, the more superficial and larger ones as elevated, bluish or reddish, raspberry-like, blanching, compressible structures (Fig. 21.1). Palpable phleboliths are sometimes present.