Phakomatosis pigmentovascularis (PPV) is a rare congenital syndrome that consists of the coexistence of a capillary malformation and a cutaneous pigmented lesion. Both are typically present at birth and affect all racial and ethnic groups. According to the most recent classification system, PPV can be divided into 5 main subtypes:
Each of these subtypes may be skin limited or may have associated systemic manifestations, most commonly Sturge-Weber syndrome or Klippel-Trenaunay syndrome. Neurologic, ocular, musculoskeletal, and/or visceral abnormalities may be present. It is estimated that systemic findings exist in up to 50% of cases.
The pathophysiology of PPV is poorly understood. One theory suggests abnormalities in neuroectodermal precursor cells that later differentiate into melanocytes and vasomotor nerve cells. Mosaic-activating mutations in PTPN11 have been identified in patients with PPV type 3, as have mosaic-activating mutations in GNA11 and GNAQ in types 1, 2, and 4.