Urticaria pigmentosa is a skin disease, which is a form of urticaria as well as mastocytosis, in which you find brown, intensely itching patches on the skin. On rubbing the spots, one gets hives or urticarial patches.
It is one of the forms of mastocytosis. For understand mastocytosis, we need to understand a bit about mast cells. Mast cells are normal cells found in the skin all over the body. Mast cells contain certain granules which when activated or stimulated, leading to the release of histamine and other such chemicals, leading to the condition called mastocytosis. You may say, mast cells are inflammatory cells.
Urticaria pigmentosa is most commonly seen in infants and children but can also be found in adults.
The exact cause of this uncommon disease is unknown but recent research suggests a genetic change in a protein (called c-kit) on the surface of mast cells may result in the abnormal proliferation of these cells.
Variety of factors can cause or worsen the symptoms of urticaria pigmentosa:
- Physical stimuli such as heat, friction, and excessive exercise
- Bacterial toxins
- Eye drops containing dextran
- Emotional stress
- Brownish lesions on the skin are seen typically around chest and forehead.
- Rubbing the skin sore causes hive-like bump.
- A fluid-filled blister may form if it is scratched, especially seen in younger children.
- The face may become flushed.
- In severe cases, diarrhea, headache, and palpitation may be seen.
A typical presentation called Darier’s sign is observed in Urticaria pigmentosa. By rubbing one of the brown patches the rubbed area becomes reddened, swollen and itchy. This confirms the presence of mastocytosis
Something about mast cells:
Mast cells are normally widely distributed in the skin. They contain granules that contain histamine and other chemicals. When the mast cell is disturbed, these chemicals are released into the surrounding skin. The chemicals make the blood vessels leaky, resulting in localized itching, swelling, and redness.
Diagnosis and Investigations:
- The disease is most often diagnosed clinically
- Doctors can confirm the presence of mast cells by rubbing the skin. If hives appear, it most likely signifies the presence of urticaria pigmentosa.
- Skin biopsy shows an increase in mast cells and confirms the diagnosis.
If there are any symptoms suggesting internal involvement the following tests may be helpful
- X-rays of skull and long bones may show areas of bone thinning or a diffuse ground glass appearance
- Urinary histamine levels or 1,4-methylimidazole acetic acid may be elevated
- It goes away on its own until the time of puberty in 50% of the cases but medication is required as it is a troublesome disease.
- In adults, it may develop into a more serious condition called systemic mastocytosis.