What is pityriasis rubra pilaris

Pityriasis rubra pilaris (PRP) is the name given to a group of rare skin disorders that present with reddish-orange colored scaling patches with well-defined borders. They may cover the entire body or just parts of the body such as the elbows and knees, palms and soles.

The name pityriasis rubra pilaris means scaling (pityriasis), redness (rubra) and involvement of the hair follicles (pilaris).

Often there are areas of uninvolved skin, particularly on the trunk and limbs, which are referred to as islands of sparing.

The palms and soles are usually involved and become diffusely thickened and yellowish (palmoplantar keratoderma). Pityriasis rubra pilaris is often initially mistaken for another skin condition, usually psoriasis.

Several types of pityriasis rubra pilaris are currently recognised including:

• Classical pityriasis rubra pilaris of adult onset
  • Accounts for 50% of all pityriasis rubra pilaris cases
  • Good prognosis with 80% of patients going into spontaneous remission within 3 years
  • After remission, relapses are uncommon
  • May be associated with underlying malignancy
• Atypical pityriasis rubra pilaris of adult onset
  • Accounts for 5% of all pityriasis rubra pilaris cases
  • May persist for 20 years or more
  • Often has an eczematous component
• Classical pityriasis rubra pilaris of juvenile onset
  • Accounts for 10% of all pityriasis rubra pilaris cases
  • Usually occurs between 5 and 10 years old
  • Often follows an acute infection of any type
  • Spontaneous remission within 1 year
• Circumscribed juvenile pityriasis rubra pilaris
  • Accounts for 25% of all pityriasis rubra pilaris cases
  • Occurs in prepubertal children
  • Usually confined to palms, soles, knees and elbows
  • Long term outcome unclear but possible improvement in late teens
• Atypical juvenile onset pityriasis rubra pilaris
  • Accounts for 5% of all pityriasis rubra pilaris cases
  • Sometimes inherited; may overlap with types of ichthyosis
  • Occurs at birth or early in childhood and is very persistent
• HIV-associated pityriasis rubra pilaris
  • The disease tends to be resistant to standard therapies

Figure 1. Pityriasis rubra pilaris

Can pityriasis rubra pilaris be cured?

The outlook for pityriasis rubra pilaris depends on the type. Treatment helps but it cannot be guaranteed to clear either of the two most common types. The ‘classic adult type’ often resolves after two or three years, but it may persist for longer. The classic juvenile type usually resolves on average in about one year while the circumscribed juvenile type tends to persist.

Is pityriasis rubra pilaris hereditary?

Pityriasis rubra pilaris is usually not hereditary but there is a rare genetic type.

What causes pityriasis rubra pilaris?

The cause of pityriasis rubra pilaris is unknown. Pityriasis rubra pilaris is not an infection and cannot be passed on to others. Pityriasis rubra pilaris is usually sporadic but in some forms, it may be partially inherited. Pityriasis rubra pilaris may occur in any race, and males and females are equally affected. Pityriasis rubra pilaris is occasionally precipitated by a drug, such as sorafenib, insulin, imatinib, telaprevir, and vaccinations.

Pityriasis rubra pilaris signs and symptoms

Symptoms of pityriasis rubra pilaris:

• The rash can be itchy in its early stages.
• Thick skin on the palms and soles can split and become painful. Walking may be sore.
• Shivering, heat and fluid loss may occur if the rash covers large areas of skin.

Classical adult-onset pityriasis rubra pilaris

The main features of the ‘classic adult type’ of pityriasis rubra pilaris are as follows:

• The rash usually starts suddenly on the scalp and spreads to cover much of the trunk.
• The patches are dry, scaly and red with an orange tinge and have well defined edges. Patches may join together to cover large areas of skin. Occasionally, people with pityriasis rubra pilaris become red all over; this is called erythroderma.
• ‘Spared areas’, where there is no rash, can often be seen lying inside the main patches of redness.
• Rough dry plugs in the hair follicles can often be seen or felt within the red patches, and also in the ‘spared areas’.
• The palms and soles thicken and have an orange color. The nails may thicken and may be discolored and sometimes shed.

Classical adult-onset pityriasis rubra pilaris most often starts on the head, neck and upper trunk as a red scaly rash. Often there is a solitary lesion but within a few weeks multiple patches appear and they join together to form groups of reddish-orange lesions. Over a few weeks, these spread downwards and may cover most of the body (erythroderma).

Rough, dry plugs can be felt within the patches and are due to plugged hair follicles, often most obvious on the backs of the fingers. Patients may also complain of itching in the early stages of the disease.

The palms and soles become thickened and yellow coloured in pityriasis rubra pilaris. Cracks may develop which can be painful and make walking and using the hands difficult. The nails may become thickened and discoloured at the free nail edge and may show linear black streaks (splinter hemorrhage). The hair may thin considerably.

Juvenile-onset pityriasis rubra pilaris

Pityriasis rubra pilaris in childhood can be classical (generalized) or circumscribed (limited in extent). The features of the ‘circumscribed juvenile type’ are well-defined red patches with hair follicle plugs on the fronts of the knees and a yellowish thickening of the palms and soles. The appearance is similar to in adults, with prominent thickening of the skin of the palms and soles. Other affected areas can be orange-red in color with follicular prominence.

How is pityriasis rubra pilaris diagnosed?

Pityriasis rubra pilaris diagnosis is made by examination of the skin and can be confirmed by a skin biopsy. Skin biopsy means that a small piece of skin is removed under a local anaesthetic and examined under the microscope.Your doctor will probably refer you to a skin specialist to confirm the diagnosis. There is no blood test for pityriasis rubra pilaris. The different types of pityriasis rubra pilaris may look like psoriasis and are often mistaken for psoriasis.

Pityriasis rubra pilaris treatment

The value of treatment is difficult to assess, as the clinical course is so variable for each of the different types of pityriasis rubra pilaris. Patients with classical adult onset pityriasis rubra pilaris may present very unwell with acute erythroderma and may require hospital admission for skin care, fluid replacement, and other supportive care.

Creams or ointments applied to the skin may be all that is required if the pityriasis rubra pilaris is mild. Topical medications such as emollients may be used to relieve symptoms of dryness and cracking.

• Steroid creams and ointmentssoothe but probably do not alter the duration of the rash.
• Emollients recommended by your doctor or specialist are a very important part of treatment to help dry skin and restore the barrier function of the skin. The emollient should be applied liberally.

Tablet medication may be needed if the pityriasis rubra pilaris is severe. These medications should only be prescribed by a dermatologist as monitoring of blood tests is necessary:

• Pityriasis rubra pilaris often improves if treated with a retinoid drug such as acitretin.
• Methotrexate, an immunosuppressant drug, may help pityriasis rubra pilaris.
• The ‘circumscribed juvenile type’ usually only requires the topical applications mentioned above.

Systemic treatments include:

• Methotrexate
• Acitretin
• Isotretinoin
• Pityriasis rubra pilaris has been reported to clear with etanercept and ustekinumab (IL-12/IL-23 blockade).

Pityriasis rubra pilaris prognosis

In general, the inherited forms of pityriasis rubra pilaris tend to persist throughout life whilst the sporadically acquired forms tend to resolve spontaneously eventually after one to three years.