Pityriasis rotunda is an uncommon acquired dermatosis related to a disorder of keratinization that was described first in 1906. This dermatosis was also called pityriasis circinata and "pseudo-ichtyose acquise en taches circulaires." It is characterized by hyperpigmented or hypopigmented, sharply defined, circular or oval scaly plaques of variable size, which develop on the trunk and proximal parts of the limbs. Pityriasis rotunda, not commonly encountered in some regions of the world, is not always easy to diagnose.
The etiology of pityriasis rotunda is not established. Authors have attached it to various disorders of keratinization such as ichthyosis vulgaris, late-onset congenital ichthyosis, and acquired ichthyosis. Pityriasis rotunda is also considered a potential paraneoplastic dermatosis since it may be observed during certain malignancies, mainly hepatocellular carcinoma in South African black patients but also in the following:
Pityriasis rotunda is also associated with several systemic diseases, such as:
Pityriasis rotunda affects both genders equally, although certain authors noticed a slight female predominance. The age for the diagnosis ranges from 20 to 45 years, with extremes of 2 and 87 years. There is a particular racial and geographic distribution for pityriasis rotunda. Most cases are reported in Japan and among West Indian and South African blacks. Case reports of pityriasis rotunda in black Americans are less common, and the frequency of the disease on the North American continent is not known. Cases of pityriasis rotunda among Caucasians are also rare. Mainly, cases are reported in Mediterranean patients, especially from Sardinia, Italy. Familial cases may also be observed and likely have a hereditary determinism which may be an autosomal dominant transmission.
Hashimoto et al. described a diminished expression of loricrin and filaggrin in pityriasis rotunda lesions. According to Yoneda et al., a complete absence of the profilaggrin-N terminus domain is observed in the lesional skin. Makino et al. reported a decrease in expression of epidermal filaggrin 2, as seen in ichthyosis vulgaris, atopic dermatitis, and psoriasis vulgaris.
Histopathology of pityriasis rotunda lesions can reveal variable findings including hyperkeratosis which is mainly ortho-keratotic but can be para-keratotic, with plugs observed within hair follicles, elongated rete ridges, a diminished or absent stratum granulosum, slight spongiosis, enhanced pigmentation of the basal layer, pigmentary incontinence, and perivascular infiltrate of small lymphocytes. Periodic acid-Schiff (PAS) stain for fungus is negative. These changes are similar to those observed in ichthyosis vulgaris. However, the histopathological aspect may be normal.
Grimalt et al. performed an ultrastructural study on biopsies from pityriasis rotunda lesional skin. They noted the existence within the epidermis of vacuoles of lipid and crystal-like inclusions. Granules of keratohyalin were normal, and keratinosomes were increased. The stratum granulosum was reduced to one layer. The cementing substance connecting corneocytes was abundant. These findings were suggestive that pityriasis rotunda was more related to congenital ichthyosis than to ichthyosis vulgaris.
The diagnosis of pityriasis rotunda usually is based on clinical examination. Skin lesions are generally asymptomatic or mildly symptomatic. Pityriasis rotunda plaques are scaly, dry, sharply defined and round with prominent hair follicles but no inflammatory erythema. Scales may be highlighted by scratching the plaques. The lesions appear hypopigmented in fair-skinned patients and hyperpigmented in dark-skinned patients. The plaques of pityriasis rotunda may be confluent. Their size is variable (1 cm to more than 20 cm), and their number ranges from one to dozens but rarely exceeds 100. Pityriasis rotunda affects mainly the trunk (back and abdomen), buttocks and proximal parts of the limbs (thighs and arms). The face, hands, and feet are usually not involved. In some patients, associated skin lesions of ichthyosis vulgaris may be observed. A familial history of ichthyosis vulgaris has been reported in certain patients with pityriasis rotunda.
Grimalt et al. proposed a classification of pityriasis rotunda. A first subtype consists of less than 30 hyperpigmented patches, occurring mainly in black and Asian persons. In this subtype, no similar familial cases are seen, but associated diseases are frequently described, for example, malignancies (solid tumors and hemopathies), systemic diseases, and infections. A second subtype is characterized by more than 30 hypopigmented patches, occurring mainly in white patients who have a familial history of similar skin lesions. There usually is no underlying disease. This classification is schematic since overlap cases have been reported.
The clinical differential diagnosis includes tinea versicolor, erythrasma, tinea corporis, nummular eczema, early-stage mycosis fungoides, fixed drug reaction, pityriasis rosea, pityriasis alba, figurate erythema, and leprosy.
Mycological examination of scaly material removed from lesional skin (direct microscopy using potassium hydroxide, and fungal culture) is useful to rule out a dermatomycosis. Wood light examination is used if erythrasma is suspected.
Management of pityriasis rotunda is often challenging. Topical corticosteroids, antifungal agents, emollients, tars, and keratolytic topicals (salicylic acid and lactic acid) are poorly efficient. Retinoids, either topicals (retinoic acid and tazarotene) or oral (etretinate) have been used with little or no success in pityriasis rotunda. Treatment with vitamin D3 analogs such as calcipotriol leads to a progressive improvement in the lesions in a small number of patients.
However, for patients with comorbidities, successful treatment of the underlying disease often leads to remission of pityriasis rotunda lesions.
Skin lesions of pityriasis rotunda have a chronic course and can persist for months to years, with alternating periods of exacerbation (especially during winter or pregnancy) and remission.
Follow-up of pityriasis rotunda skin lesions without treatment is the other option because of possible spontaneous resolution. Since underlying diseases, mainly malignancies, have been associated with pityriasis rotunda, physicians should be aware of the importance to rule out such diseases based on anamnesis, physical examination, and the appropriate investigations.
Pityriasis rotunda is a rare skin disorder which is not easy tp diagnose. The condition may be seen by the primary care provider or nurse practitioner but because of the complexity in diagnosis, it is best managed by a dermatologist. Once diagnosed, the management of pityriasis rotunda is often challenging. Topical corticosteroids, antifungal agents, emollients, tars, and keratolytic topicals (salicylic acid and lactic acid) are poorly efficient. Retinoids, either topicals (retinoic acid and tazarotene) or oral (etretinate) have been used with little or no success in pityriasis rotunda. Treatment with vitamin D3 analogs such as calcipotriol leads to a progressive improvement in the lesions in a small number of patients. The skin condition can take months or even years to disappear.
However, for patients with comorbidities, successful treatment of the underlying disease often leads to remission of pityriasis rotunda lesions. Because of the few cases, there are no evidence based guidelines on the management of this disorder.
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