Pityriasis rosea is a skin disease with a rash that can be seen at any age, but is most often encountered between the ages of 10 and 35. It is a common skin disease that can cause reddish-brown, scaly rashes. Pityriasis means scaling, and rosea means rose-coloured or pink. The rash usually heals on its own without treatment. Healing usually takes 6-8 weeks, and sometimes longer. The rash may last a few weeks or even years. The disease usually leaves no permanent mark, but in people with darker skin, brown patches may remain that fade over time.
Pityriasis rosea usually begins with an oval patch of redness called the herald patch on the chest, back, abdomen or hips, followed by other smaller rashes.
The disease is seen mostly in older children and young adults. The most common age range is 10 to 35, but it can be seen in any age group. It appears mostly in the spring and autumn months. It is twice as common in women as in men.
The disease starts as a large pink patch on the chest or back. This patch is called the herald patch. Often the patch becomes ring-shaped and fades in the centre, so it may be mistaken for a fungal infection and treated with antifungal medicines. Because the rash is not a fungal infection, these creams do not help. Within a few weeks, numerous pink lesions appear, sometimes even hundreds, on the trunk, arms and legs. The rash can be seen on the neck and, rarely, on the face. These lesions are smaller than the herald patch and, again, can be confused with a fungal disease. The lesions are oval and are distributed on the back in a pattern resembling a Christmas tree. Sometimes the disease can be very severe and widespread. Half of patients have itching, which increases especially in the heat.
Occasionally other signs such as malaise and aches may be seen. The rash usually regresses within 6-8 weeks, but it can sometimes last longer. Physical activity and hot baths can make the rash worse. In some cases, the rash can recur a few months after regressing and last for a few months.
What causes pityriasis rosea?
The cause of the disease is not known. It is not caused by a bacterial or fungal infection, nor is it an allergic reaction. It is not associated with any internal disease. It is thought that a virus may cause this rash. As with other viral infections, the patient may feel unwell and tired. However, it has not been proven that the disease results from a viral infection. Unlike other viral infections, pityriasis rosea is not passed from person to person.
Pityriasis rosea has been found to be associated with upper respiratory tract infections. It sometimes appears among family members or people in close contact. Like other viral illnesses, it is more common in the spring months. In people who have had the disease once, the risk of getting it a second time is very low. Despite all these features, no virus has been proven to cause the disease. Certain medicines are known to cause a pityriasis rosea-like rash.
It is thought that people under stress have more lesions.
Symptoms of pityriasis rosea
In 97% of patients it occurs only once in a lifetime. However, the disease has certain phases, and recovery can take weeks or even months.
In the first phase of the disease, before any signs appear on the skin, symptoms of an upper respiratory tract infection such as headache, mild fever, loss of appetite, runny nose and sore throat may be seen.
In the second phase, a large, pink, oval, scaly patch of redness (also called the herald patch or mother patch) appears on the back, abdomen or chest. This lesion is usually slightly raised and single. It grows over a few days.
In the third phase (1-2 weeks after the herald patch), the disease continues to progress and lesions smaller than the herald patch begin to appear. When located on the trunk, these lesions characteristically spread from top to sides in the shape of Christmas tree branches. This phase usually lasts 6-8 weeks.
75% of patients have itching, but it is usually mild or moderate. In 25% of patients the itching is severe.
How is pityriasis rosea diagnosed?
The clinical appearance and examination are usually enough to make the diagnosis. However, in some atypical forms it may be necessary to take a biopsy and request some blood tests to rule out other diseases.
How is pityriasis rosea treated?
The most important step of treatment is telling the patient that the disease can heal without treatment. Corticosteroid creams and medicines used in allergic conditions, called antihistamines, are used to relieve itching.
In resistant cases, ultraviolet treatment can be used to relieve itching.