Let's watch this brief 3:23 clip, to get the gist of Urticaria Pigmentosa (UP). The video transcript is below, as the commentator is not easy to understand.
Urticaria pigmentosa is an uncommon rash that usually affects the neck, arms, legs and trunk of children and young adults.
The rash consists of reddish brown spots that turn into hives when they are rubbed or scratched. Sometimes, the spots will blister.
It is a type of mastocytosis, in which there are brown patches on the skin due to an abnormal collection of mast cells.It is caused by excessive numbers of inflammatory mast cells within the skin.
UP most often affects infants, with the first patches appearing at a few months of age. They are often confused with insect bites at first, but persist and gradually increase in numbers for several months or years. They can appear in any part of the body, inclusing the scalp, the face, trunk and limbs.In young children it is common for the patches to blister when rubbed. If many patches are activated at the same time, the infant may become irritable, but it is uncommon for severe symptoms to arise. Over the next few years, the UP becomes less irritable and eventually the patches fade away. By the teen-age years, most patches will have gone. In adults, UC can develop for the first time. Few or many patches appearing may be unsightly as well as itchy. Unfortunately, in adults, UP tends to be long-term. It is also more likely to be associated with internal symptoms. To check for symptoms of UP, check for the presence of mast cells. One can test for these symptoms by rubbing one of the brown patches. within a few minutes, the rubbed area becomes red, swollen and itchy. This is known as the Darier's sign and confirms the presence of Mastocytosis.
The main symptom is brownish patches on the skin. Rubbing the skin causes the hives … Younger childres may develop a fluid-filled blister through the scratch. The face may also become flushed. UP is not serious and does not require any treatment in most cases, however, the following can be helpful:
- Mast Cell Stabilisers
- Low-dose aspirin: This can help some patients, but must be taken cautiously, as aspirin can also worsen symptoms.
- Topical steroids: steroid creams applied for several months can reduce itching, but the patches tend to re-occur after a few months. Topical steroids are only valuable for limited areas.
- And lastly, photo-chemo-therapy: This form of UV radiation is the most effective treatment for adults with UP. Two or Three treatments each week are required for several months. Photo-chemo-therapy lessens the itch and improves the appearance.The UP is likely to re-occur in 6 to 12 months, but the treatment can be repeated.
Now, lets get into a bit more detail and specifics:
The majority of urticaria pigmentosa cases are caused by a point mutation at amino acid 816 of the proto-oncogene c-kit. c-kit is a transmembrane protein which, when bound to Mast Cell Growth Factor (MCGF), signals the cell to divide. Mutations in position 816 of c-kit can result in a constant division signal being sent to the mast cells, resulting in abnormal proliferation. Different mutations have been linked to different onset times of the disease. For example, the Asp816Phe and Asp816Val mutations (the aspartate normally at position 816 in the c-kit protein has been replaced with phenylalanine or valine respectively) have been associated with early manifestation of the disease (mean age of onset: 1.3 and 5.9 months respectively).
Several factors can worsen the symptoms of urticaria pigmentosa:
- Emotional stress
- Physical stimuli such as heat, friction, and excessive exercise
- Bacterial toxins
- Eye drops containing dextran
The classification of NSAIDs can be disputed. Aspirin, for example, causes the mast cells to degranulate, releasing histamines and causing symptoms to flare. However, daily intake of 81 mg aspirin may keep the mast cells degranulated. Thus, while symptoms may be worsened at first, they can get better as the mast cells are unable to recharge with histamine.
The disease is most often diagnosed as an infant, when parents take their baby in for what appears to be bug bites. The bug bites are actually the clumps of mast cells. Doctors can confirm the presence of mast cells by rubbing the baby's skin. If hives appear, it most likely signifies the presence of urticaria pigmentosa.
There are no permanent cures for urticaria pigmentosa. However, treatments are possible. Most treatments for mastocytosis can be used to treat urticaria pigmentosa. Many common anti-allergy medications are useful because they reduce the mast cell's ability to react to histamine.
At least one clinical study suggested that nifedipine, a calcium channel blocker used to treat high blood pressure, may reduce mast cell degranulation in patients with urticaria pigmentosa. A 1984 study by Fairly et al. included a patient with symptomatic urticaria pigmentosa who responded to nifedipine at dose of 10 mg po tid. However, nifedipine has never been approved by the FDA for treatment of urticaria pigmentosa.
Another mast cell stabilizer Gastrocrom, a form of cromoglicic acid has also been used to reduce mast cell degranulation.
Urticaria pigmentosa is a rare disease, affecting fewer than 200,000 people in the United States.