Urticaria pigmentosa

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Urticaria pigmentosa Classification and external resources
Irritation to the skin causes the mast cells to release histamine, resulting in the hives seen here.
ICD-10	Q82.2
ICD-9	757.33
DiseasesDB	7864
MeSH	D014582

Urticaria pigmentosa is the most common form of cutaneous mastocytosis. It is a rare disease caused by excessive amounts of mast cells in the skin that produce hives or lesions on the skin when irritated.

Contents 1 Cause 2 Prevalence 3 Diagnosis 4 Symptoms 5 Irritants 6 Treatments 7 See also 8 References 9 External links

[edit] Cause

The majority of urticaria pigmentosa cases are caused by a point mutation at amino acid 816 of the proto-oncogene c-kit^[1]. 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). ^[2][3]

[edit] Prevalence

Urticaria pigmentosa is an orphan disease, affecting fewer than 200000 people in the United States.

[edit] Diagnosis

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.

[edit] Symptoms

Urticaria Pigmentosa is characterized by excessive amounts of mast cells in the skin. Red or brown spots are often seen on the skin, typically around the chest and forehead. These mast cells, when irritated (e.g. by rubbing the skin, heat exposure), produce too much histamine, triggering an allergic reaction that leads to hives localized to the area of irritation, sometimes referred to as Darier's sign. Severe itching usually follows, and scratching the area only serves to further symptoms. Symptoms can range from very mild (flushing, hives, no treatment needed) to life-threatening (vascular collapse).

[edit] Irritants

The following can worsen the symptoms of urticaria pigmentosa:

1. Emotional stress
2. Physical stimuli such as heat, friction, and excessive exercise
3. Bacterial toxins
4. Venom
5. Eye drops containing dextran
6. NSAIDs
7. Alcohol
8. Morphine

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 81mg 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 recover.

[edit] Treatments

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.[1]

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.^[4] However, nifedipine has never been approved by the FDA for treatment of urticaria pigmentosa.

[edit] See also

• Mastocytosis
• Mast Cells
• Urticaria
• Dermatographic urticaria

[edit] References

1. ^ Cem Akin "Molecular Diagnosis of Mast Cell Disorders" Journal of Molecular Diagnostics, Vol. 8, No. 4, September 2006 Journal of Molecular Diagnostics
2. ^ Hirokatsu Yanagihori, Noritaka Oyama,Koichiro Nakamura, and Fumio Kaneko. "c-kit Mutations in Patients with Childhood-Onset Mastocytosis and Genotype-Phenotype Correlation" Journal of Molecular Diagnostics, Vol. 7, No. 2, May 2005 PMID1867517
3. ^ Karl Sotlar, Luis Escribano, Olfert Landt, Stefanie Mo hrle, Sonia Herrero,Antonio Torrelo, Ulrich Lass, Hans-Peter Horny, and Burkhard Bultmann. "One-Step Detection of c-kit Point Mutations Using Peptide Nucleic Acid-Mediated Polymerase Chain Reaction Clamping and Hybridization Probes" American Journal of Pathology, Vol. 162, No. 3, March 2003 PMID:1868096
4. ^ Fairley JA, Pentland AP, Voorhees JJ (1984). "Urticaria pigmentosa responsive to nifedipine". J. Am. Acad. Dermatol. 11 (4 Pt 2): 740–3. PMID 6491000. 

[edit] External links

• DermAtlas 27
• BC Health Guide
• About.com with Pictures
• Prevalence of Urticaria Pigmentosa
• AAFP
• The Skin Site

v • d • e Congenital malformations and deformations of integument (Q80-Q84, 757) Congenital ichthyosis Epidermolytic hyperkeratosis - Harlequin type ichthyosis - Ichthyosis lamellaris - Ichthyosis vulgaris - Netherton syndrome - X-linked ichthyosis - Zunich-Kaye syndrome Epidermolysis bullosa Epidermolysis bullosa simplex - Epidermolysis bullosa dystrophica Other skin disease Hereditary lymphedema - Mastocytosis - Meleda disease - Naegeli syndrome - Urticaria pigmentosa - Incontinentia pigmenti - Ectodermal dysplasia - EEM syndrome - Hay-Wells syndrome - Kindler syndrome - Port-wine stain - Cutis laxa - Darier's disease - Pseudoxanthoma elasticum - Keratosis pilaris DNA repair-deficiency disorder: Bloom syndrome - Rothmund-Thomson syndrome - Xeroderma pigmentosum Nail disease Leukonychia - Pachyonychia congenita Malformations of breast Amastia - Accessory breast - Athelia - Supernumerary nipple - Micromastia Hair disease Monilethrix - Sabinas brittle hair syndrome see also non-congenital (L, 680-709)