Definition

Pityriasis rosea is a skin disorder marked by the appearance of oval-shaped patches on various parts of the body. This condition is relatively common and can affect individuals of all ages, though it most frequently occurs between the ages of 10 and 35. Characterized by a large, oval rash, often found on the chest, abdomen, or back, this initial mark is known as the "Herald patch." Within a few weeks, smaller, scaly, red oval spots may emerge, spreading in a pattern that resembles a Christmas tree, giving pityriasis rosea its alternative name: the "Christmas tree rash." Pityriasis rosea typically resolves on its own within six to ten weeks and is non-contagious, rarely leaving any marks or scarring upon healing.

Causes

The exact cause of pityriasis rosea remains unclear. However, several possible causes include:

• Viral infections

Human herpesvirus 6 and 7 (HHV-6/7) are the most strongly associated with pityriasis rosea. These viruses are not the same types that cause genital herpes. They are fairly common, especially in early childhood, where they can spread through sneezing or close contact. Once contracted, these viruses remain in the body but are typically controlled by the immune system. Pityriasis rosea may occur when immunity is weakened, allowing the virus to increase and affect the body more widely.

• Drug-induced Reactions
  

Certain medications, including angiotensin-converting enzyme inhibitors (ACE inhibitors), NSAIDs, hydrochlorothiazide, captopril, barbiturates, atypical antipsychotics, D-penicillamine, imatinib, metronidazole, isotretinoin, clozapine, and clonidine, have been linked to pityriasis rosea.

• Vaccination

Vaccines such as BCG, H1N1, diphtheria, smallpox, hepatitis B, pneumococcus, and COVID-19 may also trigger pityriasis rosea.

Risk factor

Factors that may heighten the risk of developing pityriasis rosea include:

• Age
  Most commonly affects adolescents and young adults between 10 and 35 years, though it can occur in all ages.
• Gender
  More frequently found in women.
• Seasonality
  Cases tend to peak in the winter months.
• Pregnancy
  The risk may increase during pregnancy.

Symptoms

Before the rash appears, individuals often experience flu-like symptoms, including:

• Headache
• Fatigue
• Fever
• Sore throat
• Cough
• Swollen neck glands
• Loss of appetite
• Nausea
• Trouble sleeping

Early signs typically include a single, oval, raised, and scaly patch (the "Herald patch") measuring 2 to 5 cm, usually found on the back, chest, or abdomen. Within 10 days, additional smaller scaly spots, 1 to 3 cm in diameter, often spread from the upper to the lower body, forming a pattern resembling a pine tree. The rash is uncommon on the face, scalp, palms, or soles but can cause considerable itching.

In darker skin tones, the rash may appear purple-brown to dark brown, while lighter skin tends to display pinkish or salmon-colored spots.

Diagnosis

Diagnosis typically involves a consultation and physical examination. The physician will inquire about symptom onset, progression, and rash locations and will examine and feel the skin to assess any scaly areas. Generally, the diagnosis is confirmed based on the presence of the Herald patch and Christmas tree distribution. In specific cases, further tests, such as skin scrapings, blood tests, or skin biopsy, may be conducted.

Management

Pityriasis rosea usually resolves without specific treatment. Most rashes fade within 6 to 8 weeks, but full recovery may take up to five months. Management can be categorized into:

• General Care
  

The primary goal is to alleviate itching, which can be severe in about 25% of cases. Recommendations include:

• • Applying moisturizing creams for dry skin.
  • Bathing in regular water and using gentle, soap-free cleansers.
  • Cautiously exposing the skin to sunlight.

• Specific management

For relief and to speed recovery, options include:

• Medium-strength steroid creams/ointments and oral antihistamines to manage itching.
• For severe itching, zinc oxide, calamine lotion, and even oral steroids (though not recommended long-term due to recurrence risk) may help.
• Acyclovir for seven days can hasten rash healing and relieve severe itching.
• Extensive or persistent cases may respond to narrowband UVB phototherapy.

Complications

Complications are rare as the condition usually resolves spontaneously. However, intense itching can lead to excessive scratching, causing skin lesions prone to infection. In individuals with darker skin, dark brown spots may persist even after the rash has healed.

Prevention

There is no definitive way to prevent pityriasis rosea due to its uncertain cause. However, complications can be minimized by avoiding vigorous scratching.

When to see a doctor?

Most cases of pityriasis rosea resolved without intervention. However, if symptoms worsen or persist beyond three months, medical consultation is advised.

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