Pityriasis rotunda L85.01

Vidal 1886; Toyama 1906

Rare, etiologically unexplained, chronic, aphlegmatic dermatosis characterized by ideally round, sparsely infiltrated, frequently solitary, more rarely confluent ichthyosiform plaques. The clinical picture was first described in Japan under the name "pityriasis circinata". A familial cluster has been described.

Type I: Colored and Asian patients. Number of foci <30; no familial clustering. Association with malignancy in 1/3 of cases (e.g., acute myeloid leukemia).

Type II: Caucasian patients. Number of foci >30; occasionally familial cluster. No associated malignancies (Lefkowitz EG et al. 2016).

w:m=3:1; several hundred patients have been described worldwide (Al-Refu et al. 2018).

Unknown; likely "pseudoichthyosis." PR primarily affects young adults of African descent and has no gender preference. It also occurs in the Asian population.

Ages 9 to 38; PR primarily affects young adults of African descent and has no gender preference. It also occurs in the Asian population.

Occurring singly or in groups, more rarely disseminated, 3-10cm to a maximum of 20cm in size, perfectly round or oval, but also coalescing into circular figures, brown to brown-black, sharply circumscribed, dry scaling, otherwise asymptomatic, only slightly raised plaques. No itching.

Little specific image.

Discrete changes of the surface epithelium with moderate ortho-hyperkeratosis and follicular hyperkeratosis. No formation of a keratohyalin layer.

Immunohistology: Decrease of fillagrin and loricrin expression in lesional epidermis (= indication of disturbance of keratinocyte differentiation).

Pityriasis versicolor: mutiple small focal brownish plaques, often also light spots (pityriasis versicolor alba), fungal detection easily possible.

Pityriasis rosea: exanthematous, inflammatory, small focal plaques with typical scaling

Nummular dermatitis: derb infiltrated, itching, scaly, possibly weeping. Subacute disease.

Erythrasma: intertriginous, disc-like, brownish, positive intrinsic fluorescence.

Fixed drug reaction: acute inflammatory plaque resembling an erythema multiforme, possibly blistering.

Bland, greasy externals (e.g. Linola Fett, Asche Basis Creme, Linola Fett N Ölbad). Lactic acid-containing externs are preferred.

Sometimes self-limited course after months. But also chronic course over years possible; improvement in summer.

Remark. An increased incidence of carcinoma and lymphoma has been reported. An association with acute myeloid leukemia has been described (Suzuki Y et al. 2018).

The 38-year-old African American woman with a history of hyperprolactinemia, has been treated with cabergoline for 7 months. For 9 months, she noticed sharply outlined, circumscribed hyperpigmented plaques with ichthyosiform aspect. These plaques had a diameter of 3 to 15 cm. (see Fig.). The first lesions appeared on the chest and then gradually increased in size and number. The abdomen, buttocks, and upper and lower extremities were affected. The patient did not report any accompanying symptoms, especially pruritus.

Histopathological examination revealed hyperpigmentation, hyperkeratosis, parakeratosis, flattening of the str. granulosum with flattening of the papillary body; mild perivascular lymphocytic infiltrate.

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