Although knowledge of tissue response to pressure is important for understanding the mechanism of the pressure ulcer development few previous reports describe histopathological investigations on pressure ulcers. We performed skin biopsies from erythematous sites in four patients to exclude other diseases. Case 1 underwent a biopsy of an erythema of the buttocks caused by chronic pressure in the sitting position. The histopathological features were accompanied by vascular ectasia and diffuse hemorrhage, which showed the characteristics of both an erythema and a purpura. The skin biopsy of Case 2 was performed from an erythema with a bulla on the right thigh It was caused by mechanical stimulation with the rehabilitation equipment. The histopathological observation showed extensive necrosis from the epidermis to the subcutaneous fat layer. We performed a biopsy on Case 3 of an erythema with an alopecic lesion in the left temporal area resulting from prolonged sleep on that side. Inflammatory cell infiltration and fibrosis were observed around hair follicles. The skin specimen in Case 4 was obtained from an erythema of a great trochanter lesion caused by chronic pressure in the sleeping position. The epidermis became increasingly thicker, and newly formed vessels were observed at the papillary dermis. In conclusion, although each erythema looks similar macroscopically, there are various histopathological changes in the microscopical analysis. In addition, we reviewed the previous reports on the histopathological analysis of pressure ulcers.
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