Lâm sàng các tính năng của phakomatosis pigmentovascularis. (A) trước bụng và đùi phải của trẻ sơ sinh cho thấy một sự kết hợp của khu vực hồng ban flammeus-nơvi với các khu vực melanocytosis da hơi xanh của. (B) mông và đùi sau của cùng một em bé cho thấy một sự kết hợp của tính năng tương tự. | 20 Sangueza and Requena Pathology of Vascular Skin Lesions Table 1 Classification of Phakomatosis Pigmentovascularis Type Features I a ba Nevus flammeus and nevus pigmentosus et verrucosus II a b Nevus flammeus mongolian spots nevus anemicus III a b Nevus flammeus nevus spilus nevus anemicus IV a b Nevus flammeus mongolian spots nevus spilus nevus anemicus aa cutaneous involvement only b cutaneous and systemic involvement. Fig. 1. Clinical features of phakomatosis pigmentovascularis. A The anterior abdomen and the right thigh of this newborn show a combination of erythematous areas of nevus flammeus with bluish areas of dermal melanocytosis. B The buttocks and the posterior thighs of the same baby show a combination of similar features. Pathogenesis The most commonly accepted opinion is that phakomatosis pigmentovascularis results from developmental abnormalities of the vasomotor nerves derived from the neural crest and melanocytes 30 . It is thought that an alteration in the neural regulation of blood vessels could lead to the development of the vascular abnormalities seen in this condition. This is probably the explanation for the coexistence of nevus flammeus and nevus anemicus characteristic of this disease. The abnormal melanocytic component results from alterations during the migration of the neural crest-derived melanocytes which produces lesions such as the nevus of Ota nevus spilus and mongolian spot. Histopathologic Features Histopathologically there are an increased number of dilated thin-walled capillaries and venules in the upper part of the reticular dermis although occasionally superficial areas of subcutaneous fat are also involved. The melanocytic component consists of spindled-shaped dendritic melanocytes loaded with abundant melanin in their cytoplasm scattered between the collagen bundles of the dermis Fig. 2 . Sometimes the number of spindled melanocytes is sparse thus lesions of phakomatosis pigmentovascularis may be misinterpreted as nevus .
