Background
Pityriasis rotunda (PR) is a rare, idiopathic, and chronic dermatosis characterized by discrete, round, scaly, pigmented patches. [1, 2, 3, 4, 5, 6, 7, 8, 9] Pityriasis rotunda may be associated with systemic diseases (eg, hepatocellular carcinoma) in certain racially predisposed groups.
Pathophysiology
The pathophysiology of pityriasis rotunda is still not completely understood. It may be a variant of ichthyosis vulgaris. Some studies have reported lower expression of loricrin and filaggrin in lesional skin. [10, 11] Concomitant occurrence of ichthyosis vulgaris may indicate a potential etiological relationship. [12]
Etiology
The cause of pityriasis rotunda is unknown. Some authors believe it is a variant of ichthyosis vulgaris because both have similar histologic findings. [13] Some authors believe pityriasis rotunda is caused by malnutrition, but this is not universally accepted. [14] In familial cases, an autosomal dominant mode of transmission has been proposed. [3, 15, 16, 17] The presence of systemic disease appears to be common in black South African and Japanese patients, but is much less likely among white patients. [18, 19, 20]
Black South African patients
In one series of 10 black South African patients with pityriasis rotunda, 7 had hepatocellular carcinoma. Pityriasis rotunda occurred in 15.9% of 63 unselected black South African patients with hepatocellular carcinoma, which is significantly greater than its prevalence in 63 matched controls with each of the following:
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Active tuberculosis (4.8%)
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Chronic benign hepatic disease (3.2%)
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Other malignancy (0%)
In South African patients, pityriasis rotunda has also been associated with the following:
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Chronic myeloid leukemia
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Squamous cell carcinoma of the hard palate
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Tuberculosis [21]
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Liver disease
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Cardiac disease
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Nutritional disease
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Various malignancies
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Pulmonary disease
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Chronic renal failure
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Osteitis
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Chronic diarrhea
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Scleroderma
Resolution of pityriasis rotunda has been noted with treatment of the underlying malignancy. [22]
Japanese patients
In the report of 181 patients (largely Japanese) in the French-language literature, 4 cases were associated with carcinoma of the stomach, 3 with carcinoma of the liver, 1 with carcinoma of the lung, 3 with unspecified malignant tumors.
In the same series, one Japanese patient with pityriasis rotunda had multiple myeloma, while another had myeloma and hepatic cirrhosis. [23]
White patients
The association with systemic disease appears much less common among white patients. However, some cases are familial, suggesting an autosomal dominant pattern of inheritance.
In one Sardinian family, pityriasis rotunda occurred in 3 siblings, whose father had typical ichthyosis vulgaris.
In another Sardinian family, 5 of 18 affected individuals had favism (deficiency of glucose-6-phosphate dehydrogenase). Such an association is likely coincidental because favism is common among individuals from the family's place of origin. [15, 24]
American patients
Pityriasis rotunda has been reported in 7 African Americans. One patient had metastatic adenocarcinoma, one had diabetes and unexplained thrombocytopenia, while another had human T-cell lymphotropic virus type 1–associated tropical spastic paraparesis. The fourth had mild hypertension. The fifth and sixth patients did not have any associated medical conditions. The sixth patient had associated sarcoidosis. [1, 25, 26, 27, 28, 29]
Epidemiology
Frequency
United States
Pityriasis rotunda is very uncommon in America. A review of English-language literature revealed only 6 case reports from America, which described 7 patients. [1, 25, 26, 27, 28, 29]
International
Pityriasis rotunda is a well-known condition in South Africa, Japan, and Italy, with the first known reported case from Japan in 1906. [7] Pityriasis rotunda was seen in 65 (1.01%) of 6388 South African medical inpatients. Japanese investigators reported 181 cases of pityriasis rotunda in 1960. Forty-two cases, all from the Italian island of Sardinia, were reviewed in 1997. [30] In 1989, one review of the English-language literature discussed 89 previously reported pityriasis rotunda patients. Cases of pityriasis rotunda have also been reported in Israel, England, Egypt, Portugal, Tanzania, and India. [2, 31, 32, 33, 34, 35, 36]
Race
Most cases of pityriasis rotunda are from South Africa, and all seven cases from America have occurred in blacks. Pityriasis rotunda in the South African Bantu population has been associated with hepatocellular carcinoma and malnutrition. [14, 37]
In the 1960 review of 181 cases in the French-language literature (performed by Japanese investigators), 175 patients were from Japan, 4 were from Korea, and 2 were from Manchuria. [38]
Cases have been reported among West Indians living in England. [33]
Other than the cluster of 42 patients (some familial) reported from the Italian island of Sardinia, pityriasis rotunda appears to be very uncommon among whites. [30, 39]
Sex
No sex predilection has been demonstrated in several large series, although some studies have noted a slight female predominance. [10] One series had 77 males and 63 females; another had 73 males and 101 females. A report of Sardinian patients had 22 males and 20 females. [30]
Age
Lesions are often first noted in adulthood, usually when aged 20-45 years, but a patient as old as 87 years has been reported. [10] In the review of 42 cases from Sardinia, the average age of onset was estimated to be 3-7 years. [30]
Prognosis
The prognosis for pityriasis rotunda is excellent. Pityriasis rotunda lesions sometimes resolve with treatment of the associated systemic disorder or malignancy. Lesions of pityriasis rotunda are not associated with mortality, and most are asymptomatic. Pityriasis rotunda can occur with serious underlying systemic diseases, such as hepatocellular carcinoma. [37, 40]
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Nearly perfectly round, slightly hyperkeratotic, hyperpigmented, asymptomatic plaque on the trunk.
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Classic histology for pityriasis rotunda demonstrating mild hyperkeratosis and a reduced granular layer in the epidermis.
