Pityriasis rotunda (PR) is a rare cutaneous disorder of keratinization characterized by 1 or more scaly, well-defined, round or oval patches or thin plaques, which may be hypo- or hyperpigmented. Of note, most cases have been reported from Japan, Italy, the West Indies, South Africa, and Sardinia (familial).

Most cases are idiopathic, but PR has been associated with:

• Malignancy: multiple myeloma, acute myeloid leukemia, prostate adenocarcinoma, gastric carcinoma
• Infection: leprosy, tuberculosis, osteitis
• Autoimmune disease: scleroderma
• Systemic illness: diabetes mellitus, kidney disease, liver disease, heart disease, chronic obstructive pulmonary disease (COPD), hyperprolactinemia
• Other: glucose-6-phosphate dehydrogenase (G6PD) deficiency, malnutrition

PR has been classified into 2 distinct subtypes.

Type 1:

• Typically hyperpigmented
• Typically fewer than 30 lesions
• Predominantly in older Asian or Black adults
• 30% of cases associated with systemic illness

Type 2:

• Typically hypopigmented
• Typically numerous (30 or more) lesions
• Primarily in younger patients of Northern European descent
• Strong hereditary predisposition; believed by many to exist along a spectrum of congenital ichthyoses
• Typically no association with systemic illness or malignancy