Urticaria pigmentosa (UP) is a skin condition that causes lesions and itching. It 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 the skin.
This disease is most commonly seen in infants and children but adults can 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, they respond with a Darier’s sign. A Darier’s sign looks similar to hives. This is 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 this condition, mast cells can build up in other organs of the body. In extremely rare cases, mast cell leukemia or mast cell sarcoma may result.
The exact cause of UP is unknown. However, doctors 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 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 children in late childhood are more likely to have uncommon symptoms. These include:
The diagnosis of UP is based on observation of the lesions. Darier’s sign is a classic symptom that implies UP. Most lesions look similar in color and give the impression of belonging to one disease. Lesions which appear different than 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 on 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 properties)
- 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)
Patients with urticaria should avoid certain medications such as:
- opiates (morphine and codeine)
Alcohol intake should be limited or eliminated completely since it can be a trigger for urticaria.
Ninety percent of all cases affect only the skin (Ritambhra et al. 2001). 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.