Multibranched Acquired Periungual Fibrokeratoma

decompression. Another possible explanation includes induction of nitric oxide synthase by sildenafil, stimulating further cGMP-mediated vasodilation,5 permitting lymphatic dilatation and enhanced lymphatic drainage; endothelial nitric oxide synthase has also been shown to mediate lymphangiogenesis.6 Novel effects of sildenafil on LM tissue should also be considered. A lack of PDE5 expression in LM endothelium in our study suggests that sildenafil is likely to produce decompression of LM via indirect effects on adjacent smooth muscle. We propose that sildenafil may mediate relaxation of perivascular smooth muscle in LM tissue, allowing decompression of dilated lymphatic spaces; additional studies to elucidate specific physiologic effects of sildenafil in LM are warranted.