Laboratory Studies

Scrapings of pityriasis rotunda skin lesions can be examined using potassium hydroxide mount and sent for fungal culture to rule out tinea corporis and other dermatomycoses.^[10]Examination with a Wood light is useful in cases suggestive of extraflexural erythrasma.

Imaging Studies

For pityriasis rotunda, use history and physical examination findings directed toward any underlying systemic diseases to guide further laboratory and imaging studies.

Consider investigations into the possibility of hepatocellular carcinoma in black South African patients with pityriasis rotunda.^[42]

Procedures

Skin biopsy is often useful to help exclude other diseases listed in Differentials.

Histologic Findings

Histopathological features vary, but they primarily consist of hyperkeratosis and basal layer hyperpigmentation.^[42]Hyperkeratosis may present as orthokeratotic or parakeratotic. Other findings may include plugs within hair follicles, a diminished or absent granular layer, pigmentary incontinence, mild spongiosis, elongated rete ridges, and lymphocytic perivascular infiltrate.^[10]See the image below.

Classic histology for pityriasis rotunda demonstrating mild hyperkeratosis and a reduced granular layer in the epidermis.

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Treatment & Management

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Hashimoto Y, Suga Y, Chikenji T, Matsuba S, Mizoguchi M, Kakuta M, et al. Immunohistological characterization of a Japanese case of pityriasis rotunda. Br J Dermatol. 2003 Jul. 149 (1):196-8. [QxMD MEDLINE Link].
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Media Gallery

Nearly perfectly round, slightly hyperkeratotic, hyperpigmented, asymptomatic plaque on the trunk.
Classic histology for pityriasis rotunda demonstrating mild hyperkeratosis and a reduced granular layer in the epidermis.

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Author

Jaggi Rao, MD, FRCPC Clinical Professor of Medicine, Division of Dermatology and Cutaneous Sciences, Director of Dermatology Residency Program, University of Alberta Faculty of Medicine and Dentistry, Canada

Jaggi Rao, MD, FRCPC is a member of the following medical societies: American Academy of Dermatology, American Society for Dermatologic Surgery, American Society for Laser Medicine and Surgery, Canadian Dermatology Association, Canadian Medical Association, Canadian Medical Protective Association, Pacific Dermatologic Association, Royal College of Physicians and Surgeons of Canada

Disclosure: Nothing to disclose.

Coauthor(s)

Kaushik P Venkatesh, MBA MD Candidate, Harvard Medical School

Disclosure: Nothing to disclose.

Specialty Editor Board

Richard P Vinson, MD Assistant Clinical Professor, Department of Dermatology, Texas Tech University Health Sciences Center, Paul L Foster School of Medicine; Consulting Staff, Mountain View Dermatology, PA

Richard P Vinson, MD is a member of the following medical societies: American Academy of Dermatology, Texas Medical Association, Association of Military Dermatologists, Texas Dermatological Society

Disclosure: Nothing to disclose.

Chief Editor

Dirk M Elston, MD Professor and Chairman, Department of Dermatology and Dermatologic Surgery, Medical University of South Carolina College of Medicine

Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology

Disclosure: Nothing to disclose.

Additional Contributors

James W Patterson, MD Professor of Pathology and Dermatology, Director of Dermatopathology, University of Virginia Medical Center

James W Patterson, MD is a member of the following medical societies: American Academy of Dermatology, American College of Physicians, American Society of Dermatopathology, Royal Society of Medicine, Society for Investigative Dermatology, United States and Canadian Academy of Pathology

Disclosure: Nothing to disclose.

Andrew Lin, MD, FRCPC  Associate Professor, Department of Internal Medicine, Division of Dermatology, University of Alberta

Andrew Lin, MD, FRCPC is a member of the following medical societies: American Academy of Dermatology, Royal College of Physicians and Surgeons of Canada

Disclosure: Nothing to disclose.

Andrei I Metelitsa, MD, FRCPC Assistant Clinical Professor, Section of Dermatology, University of Calgary Faculty of Medicine, Canada

Andrei I Metelitsa, MD, FRCPC is a member of the following medical societies: American Academy of Dermatology, American Society for Dermatologic Surgery, American Society for Laser Medicine and Surgery, Canadian Medical Protective Association, Canadian Dermatology Association

Disclosure: Nothing to disclose.

Pityriasis Rotunda Workup

Laboratory Studies

Imaging Studies

Procedures

Histologic Findings

References

Tables

Contributor Information and Disclosures

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