Pityriasis Rosea

Pityriasis rosea - What is pityriasis rosea?

Pityriasis rosea is a common skin condition that is manifested by a distinctive skin rash that appears red, scaly and in patches all over the body. The rashes are often itchy and may be severe in three fourths of the cases.

The condition usually goes away without treatment in three months or so. The rash begins as one single large patch called the “herald patch” and this is followed by a spread to other sites like chest, back, arms and legs. 1-7

This patient presented with a generalized rash due to the skin ailment “pityriasis rosea”, the etiology of which is unknown. Pityriasis rosea is a harmless, yet itchy, scaly skin disease often found in people 10–35yrs of age. Initially, most people develop one large scaly “herald patch”, and within 1-2wks, smaller pink patches can occur on the trunk, arms and legs. Image Credit: CDC/Richard O. Deitrick

When to seek help for pityriasis rosea

Although not harmful or complicated, the itching may be irritating and may cause disturbance in sleep and daily activities. Physicians may be contacted for evaluation of the situation if the itching is severe and patient is unable to cope.

In addition, those who have symptoms for more than three months, or who have a rapidly spreading rash or develop bleeding or pus leakage from the skin lesions need to consult with their physicians as soon as possible.

Causes of pityriasis rosea

The exact cause of this skin condition is unknown. Some studies show that the cause may be viral in origin. It occurs most often in the fall and spring. Although no bacteria, virus, or fungus has ever been found in these rashes it is thought that herpes viruses 6 and 7 may play a role.

Studies have suggested that some drugs may lead to drug-induced pityriasis rosea. These include:

  • barbiturates (sedatives)

  • bismuth

  • captopril (used in high blood pressure)

  • gold (used in rheumatoid arthritis)

  • metronidazole (antibiotic)

  • D-penicillamine (chelating agent used in certain poisonings)

  • isotretinoin (anti-aging skin preparation)

However, despite the infection theory, pityriasis rosea is not contagious and does not spread from person to person by mere physical contact. It may still occur in more than one person in a household at a time.

Who gets pityriasis rosea?

Pityriasis rosea is quite common in people. Some estimates show that 1 in 50 people who visit a skin specialist present with pityriasis rosea. Around 0.15% of the population is affected by this condition.

The common age group affected are older children and younger adults between 10 and 35 years of age. However, extremes of ages like in infants less than a year or in eighty year olds have been reported. Women are affected twice as much as men and the reason for this gender difference is unknown.

Usually people get the condition only once in their lifetime. However, one in 50 may develop the condition more than once or repeatedly.

Diagnosis of pityriasis rosea

Diagnosis is made by clinical presentation and appearance of the rash in most cases. In some patients blood may be tested for other conditions like Syphilis that may manifest with a similar rash. Sometimes a skin biopsy is advised to check the skin cells and detect abnormal histology or pathology in the cells.

Treatment of pityriasis rosea

Most of the cases of pityriasis rosea clear up with no therapy within three months. The rash may disappear in 3 months or 12 weeks or so. In some it may last up to 6 months.

Treatment consists of moisturisers or emollient creams. These soothe the skin and prevent itching. For itching and inflammation control creams with Corticosteroids or pills with Antihistamines (antiallergy medications) may be prescribed.

If there is secondary bacterial infection of the skin rashes, an antibiotic antibacterial cream or ointment may be prescribed. Ultraviolet ray exposure may help some people with the condition. These however need to be performed under supervision.

Causes of pityriasis rosea

Pityriasis rosea is a common skin condition that affects 0.15% of the general population. The condition often occurs in older children and young adults between ages 10 and 40 years and is rare among elderly and infants.

The condition has been described for more than two centuries and has a characteristic rash that begins with a small patch called the “herald patch”. This is followed by spread of a red, scaly, itchy rash to the chest, back, arms and legs. Women are at a slightly higher risk of this condition. 1-7

Is pityriasis rosea an infection?

The exact cause of this condition is still unknown. There are certain factors that lead to the belief that this may be caused by a viral infection.

The reasons for this belief is that pityriasis rosea tends to occurs in epidemics and affects large groups of persons together in a community especially during spring and autumn seasons. This could mean an infectious agent is responsible for the condition. In addition, recurrence is rare and this means that persons getting the rash may develop long lasting immunity to the infectious agent responsible for the condition.

Another significant sign that there could be an infectious agent behind pityriasis rosea is that more than 50% of the patients have some symptoms of feeling unwell before the appearance of the herald patch. This precedence of rash with general feeling of being unwell (termed prodromal symptoms) is common in cases of other viral infections. The course of the disease is also well defined and similar for most affected persons and follows a pattern much like other viral infections like measles or chicken pox.

In addition, some patients also show an increase in B lymphocytes and a decrease in T lymphocytes along with increase in Erythrocyte sedimentation rate (ESR). Lymphocytes are white blood cells that fight against infections so their rise is also significant. In addition, many infections show a rise in the ESR.

What may be causing pityriasis rosea?

Some studies have suggested that a virus may be causing pityriasis rosea. When seen under an electron microscope viral changes and virus particles have been noticed. However ,blood tests for antibodies against the viruses or special tests like polymerase chain reaction for viruses have not been positive to pinpoint a specific virus causing the condition.

Some studies have implicated Human Herpes Virus 6 and 7 in causation of pityriasis rosea. Other infections that need to be considered as causative agents of this condition include Legionella pneumoniae, Chlamydia pneumoniae and Mycoplasma pneumonia. However, these have not been proved.

Studies have suggested that some drugs may lead to drug-induced pityriasis rosea. These include:

  • barbiturates (sedatives)
  • bismuth
  • captopril (used in high blood pressure)
  • gold (used in rheumatoid arthritis)
  • metronidazole (antibiotic)
  • D-penicillamine (chelating agent used in certain poisonings)
  • isotretinoin (anti-aging skin preparation)

Despite these speculations, and occurrence of the rash in more than one person in a household at a time and more than one person in the community at a time, the disease is not contagious and does not spread from one person to another by touching.

Symptoms of pityriasis rosea

Ptyriasis rosea is a common skin condition and the symptoms often progress in three distinct stages. The first and second stages may be missed or may not occur in many patients.

The condition commonly affects older children and adults between ages 10 to 40 and peaks in age groups of 25 to 30. There is a slightly higher incidence among women but the reasons for this are unclear.

Elderly over eighty and young infants below 1 year of age are seldom affected. The exact cause of this condition is unclear but it is suspected that this may be caused by a viral infection. 1-7

Symptoms may be outlined according to the stage of the condition.

Prodromal (initial) symptoms of ptyriasis rosea

These occur in less than half of the affected individuals. These symptoms may last a week or so in these individuals. It includes:

  • a high temperature or fever of 38ºC or 100.4ºF or above

  • an upset stomach

  • headache

  • loss of appetite

  • pain in the joints

  • a general feeling of being unwell called malaise

Second stage symptoms of ptyriasis rosea

The second stage is the beginning of the rash stage. There is beginning of a red, oval patch of scaly skin that ranges from a size of 2 to 10 cm (0.8-4 inches) called the “herald patch”. This appears typically on the trunk over the abdomen or the chest.

The herald patch may also occur less commonly at other sites like genitals, scalp or face. The herald patch grows progressively over days.

Generalized skin rash

Thereafter a generalized skin rash appears. This usually takes a few days to two weeks from the first appearance of the herald patch.

These rashes are small, raised and red patches that are between 0.5 - 1.5cm in size. These appear over the chest, abdomen, arms, legs (thighs), neck etc. The face is usually unaffected.

The patches are commonly distributed in a ‘Christmas tree pattern’ on the upper back and a V shaped distribution over the chest. The rash extends as downward slanting triangular lines over the sides that give it an appearance of a Christmas tree or a fir tree.

In Caucasians and light skinned patients the rash appears pinkish or reddish in color. In dark skinned individuals these patches may appear grey, dark brown or black. The rash is usually not painful but in three fourths of all cases it may be itchy.

Itchiness may be mild in some but may range in severity and some people may develop severely itchy lesions. Itchiness worsens when the person is hot, sweating, wearing tight clothing or comes in contact with water.

Rarely some patients may develop plaques of patches and ulcers within their mouth. Both the herald patch as well as the secondary rash usually clears within three months or around 12 weeks. In some, the symptoms may persist for up to six months. Once the rash has healed there may be a darkening or lightening of the skin. This usually normalizes without treatment in a few months. There is no scarring with pityriasis rosea.

When to seek medical help

Medical help should be sought if the symptoms of itchiness are troublesome or if they are interfering with sleep or daily activities.

Medical help should be sought promptly if any of the following are the case:

  • those who have symptoms for over five months

  • those with rash that covers arms and legs but spares the trunk

  • those with a rash that is spreading rapidly over the body

  • the patches are leaking blood, clear fluid or pus

This is because these symptoms may indicate that this may be a different rash than pityriasis rosea.

Commonly skin conditions like psoriasis, sexually transmitted infection (STI) and skin manifestations of syphilis may need to be ruled out in these cases.

Diagnosis of pityriasis rosea

Pityriasis rosea is a common skin condition affecting 0.15% of the general population. This condition is more often than not diagnosed clinically by appearance and symptoms.

The lesions of the condition often start with a herald patch over the chest or abdomen followed by a more generalized rash over the chest, abdomen, legs and arms. The characteristic appearance of the rash is alike a Christmas tree with triangular lines extending from the center of the back to the sides. (1-5)

Atypical appearances of pityriasis rosea

Other atypical appearances of pityriasis rosea include; (1-5)

  • Inverse pityriasis rosea - In this the arms and legs may be affected but the trunk may be spared. In children face may be involved and the armpits and groin are involved.

  • Localized pityriasis rosea - In this condition the lesion is highly localized to a single place and this makes diagnosis difficult.

  • Gigantean pityriasis rosea shows large lesions which are lesser in number.

  • Pityriasis rosea Urticata shows itchy lesions and urticarial or itchy patches all over the skin.

Other types include:

  • Pustular pityriasis rosea (with pus oozing from the lesions)

  • Vesicular pityriasis rosea (with blisters)

  • Purpuric pityriasis rosea (with bleeding spots over the lesions)

  • Pityriasis rosea that appear like erythema multiforme

Diagnosis of pityriasis rosea

Routine blood counts are prescribed. In most cases they are normal. Some patients may show a rise in white blood cell counts. In addition, there may be selective rise of lymphocytes (B lymphocytes) indicating that pityriasis rosea may be caused by an infection. There is also a raised Erythrocyte sedimentation rate (ESR) that is another marker of disease.

Sometimes a skin biopsy may be undertaken to look at the cells of the lesion more closely. The skin area is cleaned and numbed with a local anaesthetic. Then a small tissue sample is cut off from the lesion. The area is dressed with bandages.

Under the microscope the skin tissues with pityriasis rosea reveal infiltration of the skin cells with lymphocytes, histiocytes and rarely eosinophils. There are changes in the superficial cells of the skin called the epidermis with increased keratosis or dyskeratosis. In addition, some red blood cells may also be seen in the superficial skin layers.

Ruling out alternative diagnoses

While diagnosing pityriasis rosea other conditions that may lead to similar lesions need to be ruled out. This includes:

  • Drug rashes that appear as pityriasis rosea. Some drugs like Arsenic compounds, barbiturates (sedatives), bismuth, captopril (used in high blood pressure), gold (used in rheumatoid arthritis), metronidazole (antibiotic), D-penicillamine (chelating agent used in certain poisonings), sotretinoin (anti-aging skin preparation), Clonidine (used in high blood pressure), Interferon (used in viral infections), Ketotifen fumarate, Hepatitis B vaccine and Bacillus Calmette-Guérin vaccine (BCG vaccine used against tuberculosis) need to be ruled out.

  • To rule out syphilis that may lead to similar skin lesions, tests like VDRL test and Fluorescent Trepenomal Antibody test are prescribed.

  • To rule out fungal infections that may mimic pityriasis rosea. The skin lesion is scraped with a sterile blunt edge of the scalpel and the scrapings are placed on a microscope glass slide. These are then stained with special dyes and examined under the microscope.

Other conditions that need to be ruled out include:

  • Pityriasis versicolor

  • Erythema multiforme

  • Guttate Psoriasis

  • Para psoriasis

  • Seborrhoeic dermatitis

  • Nummular Eczema

  • Lichen planus