Phacomatosis pigmentovascularis (PPV) is a disorder characterized by the co-existence of vascular and pigmentary birthmarks. Signs and symptoms may include port wine stain, melanocytic nevi (commonly known as moles), epidermal nevi, dermal melanocytosis (areas of blue-gray discoloration), nevus spilus, and patches of hyperpigmentation (areas of darker skin). Other skin features may include nevus anemicus (areas of lighter skin) and café au lait spots. About half of people with PPV have systemic involvement, which means they have features affecting other areas of the body. People with systemic involvement may have neurologic, ocular (eye), or muscular abnormalities. Isolated PPV is typically a sporadic disorder that occurs for the first time in people with no family history of PPV. PPV can be caused by a somatic genetic change in the GNA11 or GNAQ gene that is present only in the affected tissues of the body. These genetic changes are not present in the blood or in unaffected tissues, which means the disorder is likely due to non-inherited genetic changes that are randomly acquired after conception. In some cases of isolated PPV, the underlying cause remains unknown.