Luciano Schiazza M.D.
Also called psoriasis alba, it’s an atypical, distinct form of psoriasis localized between the toes.
First described in 1961.
It appears as a whitish, firm, pliant plaque in intertoe areas much more between 4th and 5th digit. It is rare between the fingers.
A skin biopsy reveales histopathological findings of psoriasis, such as: iperparakeratosis with stratum granulosum usually absent or intermittent, psoriasiform hyperplasia of the epidermis, subcorneal micropustule.
White psoriasis is often mistaken for interdigital fungal infection for the macerated appearance of white patche: but palpating it, the skin is dry, firm and flexible. Sometimes there are painless fissures between and beneath the toes. Itching is usually absent.
Psoriasis patches may be present in other body sites.
White psoriasis is not a fungal infection, but secondary fungal infection can develop on it; but white psoriasis may be secondary to infection (“koebner phenomenon”).
Avoiding skin biopsy, the diagnosis of white psoriasis needs negative fungal culture or history of unsuccessfully treatments with antimycotics. Together psoriasis may be observed in other body areas.
The treatment of white psoriasis is based on drugs usually prescribed for intertriginous psoriasis (e.g. topical steroids, calcitriol ointment).