Makindo Medical Notes

Related Subjects: |Nikolsky's sign |Koebner phenomenon |Erythema Multiforme |Pyoderma gangrenosum |Erythema Nodosum |Dermatitis Herpetiformis |Lichen Planus |Acanthosis Nigricans |Acne Rosacea |Acne Vulgaris |Alopecia |Vitiligo |Urticaria |Basal Cell Carcinoma |Malignant Melanoma |Squamous Cell Carcinoma |Mycosis Fungoides (Sezary Syndrome) |Xeroderma pigmentosum |Bullous Pemphigoid |Pemphigus Vulgaris |Seborrheic Dermatitis |Pityriasis/Tinea versicolor infections |Pityriasis rosea |Scabies |Dermatomyositis |Toxic Epidermal Necrolysis |Stevens-Johnson Syndrome |Atopic Eczema/Atopic Dermatitis |Psoriasis

About

• Pityriasis rosea is a common, acute, self-limiting skin condition characterized by a distinctive rash that primarily affects the trunk and upper limbs.
• The condition often starts with a single large pink, scaly patch known as the "herald" or "mother" patch, which is typically found on the chest or back. This patch can be mistaken for ringworm initially.
• After the appearance of the herald patch, a secondary rash follows, spreading across the body in a characteristic pattern.

Aetiology

• The exact cause of pityriasis rosea is unknown, but it is thought to be triggered by a viral infection, particularly reactivation of certain herpesviruses like HHV-6 or HHV-7.
• The condition can occur in outbreaks, such as in schools, army barracks, or within families, suggesting a possible contagious aspect, though direct person-to-person spread is not well-established.
• Pityriasis rosea is more frequent in colder months, possibly due to seasonal viral activity, and predominantly affects individuals between the ages of 10 and 35 years.

Clinical Features

• The initial presentation is the appearance of the herald patch, a solitary, round or oval, pink, scaly lesion that measures between 2-5 cm in diameter. It is usually found on the trunk or upper thighs.
• Within 1-2 weeks of the herald patch, a generalized rash develops, consisting of numerous smaller oval lesions, typically 1-2 cm in size, which spread across the back, chest, and abdomen.
• The secondary rash often follows skin tension lines, forming a characteristic "Christmas tree" pattern, especially on the back.
• The rash may cause mild to moderate itching, which can be more pronounced in individuals with dry skin or those exposed to heat or sweating.
• Systemic symptoms such as fatigue, low-grade fever, headache, sore throat, or body aches may occur but are usually mild and short-lived.

Investigations

• Blood Tests: Generally normal and not typically required unless other conditions are being considered, such as fungal infections or secondary syphilis.
• Skin Biopsy: Rarely needed but may be performed to exclude other conditions like psoriasis or eczema if the presentation is atypical or the rash does not respond to treatment.
• KOH Test: A scraping test to rule out fungal infections like tinea corporis (ringworm), which can mimic the herald patch in its early stages.

Management

• Treatment primarily aims to alleviate symptoms as the rash typically resolves on its own within 6 to 8 weeks without any intervention.
• Antihistamines: Oral antihistamines like loratadine or diphenhydramine can be used to manage itching and improve sleep if pruritus is bothersome.
• Topical Steroids: Mild corticosteroids, such as Hydrocortisone cream, may be applied to reduce inflammation and itchiness in localized areas.
• Moisturizers: Regular use of emollients can help soothe the skin, especially if the patient experiences dryness or irritation.
• Phototherapy: UVB phototherapy may be considered for patients with severe or persistent cases, as it can help speed up the resolution of the rash and reduce itching.
• Patient Education: Informing patients that the condition is self-limiting and generally does not recur can help alleviate anxiety about the rash.
• Avoidance of Irritants: Patients are advised to avoid hot showers, vigorous rubbing of the skin, and wearing tight clothing to reduce irritation.

Prognosis

• Pityriasis rosea is a benign condition that usually resolves without treatment over 6 to 8 weeks, although in some cases, it may persist for up to 12 weeks.
• Most patients recover fully without complications, and the rash generally does not leave any scarring or permanent skin changes.
• Post-inflammatory hyperpigmentation or hypopigmentation may occur, especially in individuals with darker skin tones, but this typically fades over time.
• Recurrence is rare, occurring in less than 3% of cases.

Differential Diagnosis

• Tinea corporis (Ringworm): Can resemble the herald patch but usually lacks the characteristic secondary rash pattern of pityriasis rosea.
• Secondary Syphilis: May present with a widespread rash that can mimic pityriasis rosea; testing for syphilis may be warranted in sexually active individuals.
• Eczema: The rash of eczema can also appear red and scaly but is often more pruritic and associated with a history of atopic conditions.
• Psoriasis: Psoriatic plaques are typically thicker and more persistent than the lesions of pityriasis rosea and are often found on the elbows, knees, and scalp.

Conclusion

Pityriasis rosea is a benign skin disorder that typically resolves without treatment over several weeks. While the condition is self-limiting, appropriate symptom management can help alleviate discomfort during its course. Education about the natural history of the condition is important to reassure patients and prevent unnecessary worry about its appearance and course.

References

• Harmon, A. J., & Gupta, A. K. (2004). Pityriasis rosea: an update. Dermatology, 208(2), 145-152.
• Mayo Clinic. Pityriasis rosea. Available at: https://www.mayoclinic.org
• National Institutes of Health (NIH). Pityriasis Rosea. Available at: https://www.ncbi.nlm.nih.gov
• World Health Organization (WHO). Skin Conditions. Available at: https://www.who.int