Rendu-Osler-Weber disease (hereditary hemorrhagic telangiectasia, HHT) is a rare autosomal dominant disease characterized by multiple telangiectases on the skin and mucous membranes, arteriovenous malformations of internal organs with 1 case per 5000-10 000 population incidence. The pathogenesis of HHT is associated with vessel wall anomaly and dilation of postcapillary venules, while the increase in angiogenesis markers in blood serum and vessel wall contributes to the enhancement of endothelial cells proliferation and the formation of arteriovenous fistulae. Neoangiogenesis and pathology of vessel architecture are also of significant pathogenetic importance in psoriasis development. The area of vasculature in psoriatic plaque is known to be larger than in the healthy skin, and the high levels of angiogenesis markers in blood serum are detected. We present a brief literature review devoted to the history, epidemiology, etiology, pathogenesis, manifestations, diagnosis and treatment of Rendu-Osler-Weber disease. A clinical case of psoriasis exudativa in patient with HHT has been presented. Features of medical history, clinical picture and pathomorphological study in the patient have been considered. Presumably, the features of neoangiogenesis and vasculature in Rendu-Osler-Weber disease and psoriasis led to the development of an atypical clinical picture of dermatosis. The combination of diseases caused difficulties in diagnosing psoriasis and the need for interdisciplinary interaction.