Pityriasis rotunda

Pityriasis rotunda is a rare skin disease characterized by round, scaly, pigmented patches that mainly occur on the trunk, arms and legs. There are two types of pityriasis rotunda. Type 1 is seen mainly in East/Southeast Asian and South African individuals older than 60 years, and is often associated with internal disease or malignancy (cancer). Type 2 occurs in lighter skinned individuals younger than 40 years, and often in several members of the same family. Type 2 pityriasis rotunda is not associated with internal disease or malignancy. The cause of pityriasis rotunda is unknown, but it may be a variant of ichthyosis vulgaris. Type 1 most often occurs with liver and stomach cancer.^[1]

Pityriasis rotunda is very uncommon in the United States. A review of the English-language literature revealed only 5 case reports from the United States, which described 6 African American patients. However, pityriasis rotunda is a well-known condition in South Africa, Japan, and Italy. Cases of pityriasis rotunda have also been reported in Israel, England, Egypt, Portugal, Tanzania, and India.^[2]

The lesions that result from pityriasis rotunda usually do not cause specific symptoms and/or lead to serious complications. However, pityriasis rotunda can occur with serious underlying systemic diseases and cancers, such as stomach cancer and liver cancer.^[2]

Affected individuals usually have several lesions, ranging from 4 to 80, that are commonly found on the buttocks, thighs, abdomen, trunk, and upper and lower extremities. The patches are often almost perfectly circular and sharply defined with dry ichthyosis-like scaling. The lesions range between 0.5 and 20 cm in diameter and are generally isolated, although merging of lesions can create a polycylic shape. Colors range from pink to light-brown. Once the lesions develop, they usually remain unchanged throughout life unless the underlying internal disease or malignancy is treated, in which case, they resolve or improve.^[1][2]

There appear to be two types of pityriasis rotunda. Type 1 pityriasis rotunda usually affects South African and East/Southeast Asian individuals older than 60 years who tend to have associated malignancies (cancers) or systemic disease. The lesions found in those with type 1 are usually darker (hyperpigmented) than the surrounding skin; and other family members are not affected. Type 2 affects people with lighter skin who are younger than 40 years. These individuals do not have any associated malignancy or systemic diseases, but have multiple lesions that are lighter (hypopigmented) than the surrounding skin. Type 2 also tends to run in families.^[2]

The exact cause of pityriasis rotunda is unknown, but some researchers believe that it may be a variant of ichthyosis vulgaris.^[1][2] Other researchers believe that pityriasis rotunda is caused by malnutrition, but this is not universally accepted. The presence of systemic disease, which is characteristic of type 1 pityriasis rotunda, appears to be most common in South African and Japanese individuals, but is less common among Caucasians.^[2] Type 1 most often occurs with stomach cancer and liver cancer. Other conditions that type 1 pityriasis rotunda has been associated with include:^[1][2]

• Other malignancies (chronic myeloid leukemia, squamous cell carcinoma, multiple myeloma)
• Liver disease
• Tuberculosis
• Heart disease
• Lung disease
• Chronic kidney disease
• Malnutrition
• Chronic diarhhea
• Scleroderma

It has been proposed that type 2 pityriasis rotunda, which is typically inherited in families and seen in lighter skinned individuals, is inherited in an autosomal dominant manner.^[1]

There is no specific treatment for pityriasis rotunda. People diagnosed with this condition usually need to undergo medical and physical examinations and have appropriate laboratory and radiographic tests to check for internal disease or malignancies. The lesions usually improve or resolve with treatment of the underlying internal disease or malignancy. Symptomatic treatment of lesions using topical retinoids, salicylic acid ointment, and lactic acid lotion has been used.^[1] However, the lesions can be resistant to therapy.^[2]