Pityriasis rotunda, previously known as pityriasis circinata and historically referred to as tinea circinata, manifests as large circular scaly thin plaques, measuring between 10 to 30 cm. These plaques can appear hypo- or hyperpigmented and are typically found on the trunk and extremities [4].  The number of lesions has been observed to increase during the winter and decrease during the summer. The exact pathophysiology of pityriasis rotunda remains unknown. However, it is believed to involve reduced expression of filaggrin-2, particularly in the granular layer, resembling a type of acquired ichthyosis. This decreased filaggrin expression leads to increased skin thickening, resulting in the formation of scaly circles [5].  Although the term "tinea circinata" suggests a fungal origin, dermatophytes and other fungal species are not found in pityriasis rotunda lesions. The differential diagnosis for pityriasis rotunda includes tinea corporis, tinea versicolor, leprosy, and erythrasma. Potassium hydroxide testing of the scale yields negative results in pityriasis rotunda.  Although the diagnosis of pityriasis rotunda is mainly clinical, histopathological examination often reveals hyperkeratosis, hypogranulosis, and sometimes a pigmented basal layer with a mild perivascular lymphocytic infiltrate [3]. These histological features closely resemble those observed in ichthyosis vulgaris.

There are two types of pityriasis rotundas; however, some cases may not fit neatly into these categories [6]. Class 1 pityriasis rotunda presents as hyperpigmented lesions in elderly Asian or African patients, often associated with an underlying infection or malignancy, particularly gastrointestinal malignancies like hepatocellular carcinoma. Usually, fewer than 30 lesions are observed, and about 30% of cases are linked to malignancy [7]. There have been a few reported cases associated with various other cancers, including multiple myeloma [8], as well as systemic illnesses like malnutrition [9], anorexia nervosa [10], and mycobacterial diseases. Our case describes a type 1 pityriasis rotunda associated with colonic polyposis. On the other hand, class 2 pityriasis rotunda manifests as hypopigmented lesions in young adult Northern Europeans, showing a strong hereditary component and lying within the spectrum of congenital ichthyoses. In this type, more than 30 lesions are commonly seen, but it is not associated with any underlying disease.  Treatment approaches for pityriasis rotunda can be conservative since the lesions are typically asymptomatic and may resolve spontaneously. Some reported effective treatments include tretinoin cream, anti-fungal agents, lactic acid, and salicylic acids [11]. For extensive disease in type 2 pityriasis rotunda, systemic vitamin A can be used.  For cases of type 1 pityriasis rotunda, it is crucial to treat any underlying disease, as it may lead to clinical improvement of the rash.