A rare genetic capillary malformation characterized by dark red to purple birthmarks which manifest as flat, sharply circumscribed cutaneous lesions, typically situated in the head and neck region, in various members of a single family. The lesions grow proportionally with the individual, change in color and often thicken with age. There is evidence that congenital capillary malformations can be caused by somatic mosaic mutation in the GNAQ gene on chromosome 9q21. [from
SNOMEDCT_US]