Pityriasis Rotunda

Etiology

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 Black patients from South African, but also the following:

• Immunoglobulin G myeloma, multiple myeloma
• Acute myeloid leukemia
• Chronic myeloid leukemia
• Adenocarcinoma of the prostate
• Esophagus carcinoma
• Gastric carcinoma
• Squamous cell carcinoma of the palate

Pityriasis rotunda is also associated with several systemic diseases, such as:

• Malnutrition
• Diabetes mellitus
• Infections (tuberculosis, leprosy, osteitis)
• Hepatic diseases such as cirrhosis
• Chronic obstructive pulmonary disease and recurrent pulmonary infections
• Heart disease
• Female genital tract anomalies (ovarian cysts and fibroids)
• Glucose-6-phosphate dehydrogenase deficiency (favism)
• Chronic diarrhea
• Scleroderma
• Sarcoidosis
• Hormonal disorders such as hyperprolactinemia

However, researchers have not eliminated the idea that the association of some of these conditions associated with pityriasis rotunda, especially favism, could be due to chance.[4][5][6][7]

Epidemiology

Pityriasis rotunda affects both sexes 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 Black individuals in South Africa. 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.

Pathophysiology

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 the expression of epidermal filaggrin 2, as seen in ichthyosis vulgaris, atopic dermatitis, and psoriasis vulgaris.

Histopathology

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 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 pityriasis rotunda lesional skin biopsies. 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 1 layer. The cementing substance connecting corneocytes was abundant. These findings suggest that pityriasis rotunda was more related to congenital ichthyosis than ichthyosis vulgaris.

History and Physical

The diagnosis of pityriasis rotunda is usually 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 1 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.[8][9]

Grimalt et al proposed a classification of pityriasis rotunda. The first subtype consists of less than 30 hyperpigmented patches, mainly in black and Asian persons. No similar familial cases are seen in this subtype, but associated diseases are frequently described, such as 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 with 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.

Evaluation

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.

Treatment / Management

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 few patients. However, for patients with comorbidities, successful treatment of the underlying disease often leads to remission of pityriasis rotunda lesions.

Differential Diagnosis

The differential diagnoses for pityriasis rotunda include the following:

• Erythrasma
• Leprosy
• Parapsoriasis
• Pityriasis alba 
• Pityriasis rosea
• Plaque psoriasis
• Sarcoidosis
• Tinea corporis
• Tinea cruris
• Tinea versicolor