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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:
Adults or adolsecents are more likely to have uncommon symptoms. These include:
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:
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:
In adults, a form of light therapy called photochemotherapy using ultraviolet radiation has proven to be an effective treatment.
In order to encourage recovery:
People with UP should avoid certain medications, including:
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:
Unfortunately, the treatment for UP can have some unintended side effects. Side effects of prolonged treatment include:
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:
Your pediatrician may have more tips. Most cases of UP clear up by the time the child is a teenager.
Written by: Lydia Krause
Medically reviewed on: Jan 26, 2016: Steve Kim, MD
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