Prurigo chronica multiformis: Expert consensus of the Japanese Dermatological Association.

Prurigo chronica multiformis is a commonly used diagnostic designation for a peculiar subtype of prurigo in Japan, although the disease entity might not be well-recognized in other countries. Experts approved by the Japanese Dermatological Association attempted to build a common consensus on prurigo chronica multiformis, agreeing that it is a unique and important disease entity in elderly patients. Skin lesions are characterized by intensely pruritic, edematous, urticarial papules, or small macules, which gradually become solid papules/small nodules. The papules tend to aggregate and occasionally coalesce into polygonal lichenified plaques. The most commonly affected sites are the lower abdomen and lower back, although the chest, thighs, and upper back might also be involved. Common histopathological features of prurigo chronica multiformis include infiltration of lymphocytes and eosinophils in the upper dermis, with minimal epidermal changes. Basophil infiltration is also observed. The epidemiological incidence, differences in clinical manifestations by geographical location, and disease placement among other forms of prurigo and/or related skin diseases need to be further elucidated. Dermatologists should be aware of the clinical characteristics of prurigo chronica multiformis.