Pityriasis rotunda is also known as ‘pityriasis circinata’ and ‘acquired pseudo-ichthyosis’.
What is pityriasis rotunda?
Pityriasis rotunda is a rare disease characterised by round or oval scaly, pigmented patches that mainly occur on the trunk, arms and legs. There appear to be two types of pityriasis rotunda.
Type I is seen mainly in oriental and black patients older than 60 years, and is often associated with internal disease or malignancy.
Type II occurs in patients less than 40 years, and often in several members of the same family. To date no cases of type II pityriasis rotunda have been associated with internal disease or malignancy.
The appearance of lesions is the same regardless of the type of pityriasis rotunda. It is uncommon in people that have white skin.
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
Colours range from pink to light-brown. Lesions are usually darker than surrounding skin (hyperpigmented) in patients with dark skin and lighter (hypopigmented) in patients with light skin.
Several lesions are usually present, ranging from 4 to 80
Commonly situated on the buttocks, thighs, abdomen, trunk, and upper and lower extremities
Once lesions develop they usually remain unchanged throughout life unless the underlying internal disease or malignancy is treated, in which case they resolve or improve.
What is the cause of pityriasis rotunda?
The cause of pityriasis rotunda is unknown but it may be a variant of ichthyosis vulgaris. Type I pityriasis rotunda (paraneoplasticpityriasis rotunda) most often occurs with liver and stomach cancer. Other conditions that type I pityriasis rotunda has been associated with include:
Other malignancies (chronic myeloid leukaemia, squamous cell carcinoma, multiple myeloma)
Chronic renal failure
In familial cases, it has been proposed that the condition is inherited via an autosomal dominant manner.
What is the treatment for pityriasis rotunda?
Patients with pityriasis rotunda need to undergo medical and physical examinations and appropriate laboratory and radiographic tests to check for internal disease or malignancies.