Urticaria pigmentosa (UP) is an allergy-mediated skin condition that causes discolored lesions and itchy skin. The condition is characterized by the presence of too many mast cells in the skin. Mast cells are part of your immune system. Their job is to produce inflammation by releasing a substance called histamine in response to germs and other invaders. In UP, there are too many mast cells in your skin.
This disease is most commonly seen in infants and children, but adults may be affected as well. The main symptom is dark-colored lesions on the skin. The lesions may be very itchy and difficult not to scratch. When rubbed or scratched, the lesions respond with a Darier’s sign. A Darier’s sign looks similar to hives. It’s caused by the release of histamine from the mast cells.
In most children, UP goes away by puberty. Complications are typically only seen in older children or adults. Rarely, UP may evolve into systemic mastocytosis in an adult. In systemic mastocytosis, mast cells can build up in other organs of the body. In extremely rare cases, this may result in mast cell leukemia or mast cell sarcoma, which are both forms of cancer.
The main symptom of UP is brownish lesions on the skin. Rubbing the lesions releases histamines which produce intense itching along with blisters or hives (Darier’s sign).
Symptoms of UP may include:
- pruritus (itching that varies in severity and intensity)
- flushing (redness of the skin)
- overpigmentation of lesions (very dark coloring of lesions)
Adults or adolsecents are more likely to have uncommon symptoms. These include:
- tachycardia (rapid heart rate)
- nausea or vomiting
The exact cause of UP is unknown. There may be a genetic cause for some cases (the child either inherits an abnormal gene from one of their parents, or there is a gene mutation), while other cases appear for no reason at all. The inherited form of UP is very rare, with only about 50 documented cases.
Doctors do know that when the lesions are rubbed, they release histamines. Histamines are chemicals that start an immune response. Ordinarily the immune system is activated in response to germs or other invaders. In UP, there is no invader. The immune response results in itchy lesions on the skin.
The diagnosis of UP is based on observation of the lesions. Darier’s sign is a classic symptom that implies UP and most lesions look similar in color. Lesions that appear different from others may be a sign of cancer.
Possible cancers may include:
- melanoma (the deadliest of skin cancers)
- basal cell carcinoma (uncontrolled growths or lesions in the outer layer of skin)
- actinic keratosis (a precancerous scaly patch of skin caused by years of sun exposure)
Your doctor will test any unusual looking lesions for cancer. This will require a small skin sample for microscopic examination and testing. A skin biopsy will be recommended for this purpose.
There are no cures for UP. Treatment focuses on easing symptoms and controlling lesions. Your doctor will recommend a specific treatment based on the number of lesions and your tolerance. For example, painless and easy-to-apply treatments might be best for young children.
Treatment options include:
- antihistamines to relieve itching and flushing of the skin
- topical corticosteroids (gel or cream with anti-inflammation properties)
- intralesional corticosteroids (injection with anti-inflammatory steroid medications)
- hydrocolloid dressings (act like a bandage to hold medication to the skin)
- fluocinolone acetonide (a synthetic corticosteroid)
- chlorpheniramine maleate (antihistamine used to control allergic reactions)
In adults, a form of light therapy called photochemotherapy using ultraviolet radiation has proven to be an effective treatment.
In order to encourage recovery:
- do not rub the skin
- do not pick at blisters (no matter how tempting)
- do not scratch the lesions (this will only send out more histamines creating a bigger reaction)
People with UP should avoid certain medications, including:
- opiates (morphine and codeine)
Alcohol intake should be limited or eliminated completely since it can be a trigger for UP.
Most cases of UP affect only the skin. Cases where UP affects other organs are generally found in older children and adults.
Organs which may be affected by UP include:
- bone marrow
Unfortunately, the treatment for UP can have some unintended side effects. Side effects of prolonged treatment include:
- red skin syndrome (corticosteroid withdrawal)
- diabetes mellitus (glucose intolerance due to chronic use of steroid therapy)
- insulin resistance (body grows immune to the presence of insulin)
Most cases of UP appear in children. As they grow older, the majority will outgrow the disease. Lesions generally fade as a child moves into adulthood. Up to 25 percent do not outgrow the disease and retain lesions into adulthood.
There is no sure way to prevent UP. The inherited form is very rare, and even when the child has the abnormal gene, they may not ever develop UP.
However, you can prevent the disorder from getting worse. Try to help your child keep from scratching or rubbing their irritated skin to prevent the lesions from spreading:
- avoid hot baths to keep from drying out their skin and making the itching worse
- bathing in lukewarm (or cool) Aveeno oil baths have been shown to control itching
- avoid itchy, irritating clothing — try cotton or other light fabrics instead
- keep their fingernails short
- have them wear light cotton gloves to bed to prevent scratching
Your pediatrician may have more tips. Most cases of UP clear up by the time the child is a teenager.