Videocapillaroscopy in the differential diagnosis between psoriasis and seborrheic dermatitis of the scalp.

BACKGROUND: Videocapillaroscopy (VCP) can be used to explore microcirculatory modifications in skin diseases. Psoriasis shows specific capillary alterations reflecting typical histopathological changes. OBJECTIVE: To compare capillary morphology, distribution and density in psoriasis and seborrheic dermatitis of the scalp for differential diagnosis. METHODS: VCP was performed on histology-confirmed scalp lesions of 30 patients with chronic plaque psoriasis, 30 age- and sex-matched patients with seborrheic dermatitis and 30 healthy subjects. The morphology, mean density per mm(2) and mean diameter of capillary loops was measured. RESULTS: Scalp psoriasis exhibited homogeneously tortuous and dilated capillaries (bushy pattern), with a 73 +/- 17 mum (mean +/- standard deviation) diameter of capillary bushes. In contrast, scalp seborrheic dermatitis presented a multiform pattern, with mildly tortuous capillary loops and isolated dilated capillaries, but a substantial preservation of local microangioarchitecture. Mean diameter of capillary bush was significantly lower (27 +/- 4 microm; p < 0.001) and similar to that of the scalp of healthy subjects (21 +/- 5 microm). Capillary loop density was similar in patients with psoriasis (23 +/- 5/mm(2)) seborrheic dermatitis (24 +/- 2/mm(2)) and healthy scalp skin (24 +/- 3/mm(2)). CONCLUSION: VCP could be a useful noninvasive approach for differentiating between psoriasis and seborrheic dermatitis, especially when the scalp is the only affected site