Urticaria pigmentosa
2734770
221408251
2008-06-24T11:09:15Z
76.119.240.107
{{Infobox_Disease
| Name = {{PAGENAME}}
| Image = Urticaria2.JPG
| Caption = Irritation to the skin causes the mast cells to release histamine, resulting in the hives seen here.
| DiseasesDB = 7864
| ICD10 = {{ICD10|Q|82|2|q|80}}
| ICD9 = {{ICD9|757.33}}
| ICDO =
| OMIM =
| MedlinePlus =
| eMedicineSubj =
| eMedicineTopic =
| MeshID = D014582
}}
'''Urticaria pigmentosa''' is the most common form of cutaneous [[Mastocytosis|mastocytosis]]. It is a [[rare disease]] caused by excessive numbers of [[mast cells]] in the skin that produce [[Hives|hives]] or lesions on the skin when irritated.
== Cause ==
The majority of urticaria pigmentosa cases are caused by a [[Point_mutation|point mutation]] at [[Amino_acid|amino acid]] 816 of the [[Proto-oncogene|proto-oncogene]] [[C-kit|c-kit]]<ref>Cem Akin "Molecular Diagnosis of Mast Cell Disorders" Journal of Molecular Diagnostics, Vol. 8, No. 4, September 2006 [http://jmd.amjpathol.org/cgi/reprint/8/4/412 Journal of Molecular Diagnostics]</ref>. 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|aspartate]] normally at position 816 in the c-kit protein has been replaced with [[Phenylalanine|phenylalanine]] or [[Valine|valine]] respectively) have been associated with early manifestation of the disease (mean age of onset: 1.3 and 5.9 months respectively).
<ref>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 [http://www.pubmedcentral.nih.gov/picrender.fcgi?tool=pmcentrez&artid=1867517&blobtype=pdf PMID1867517]</ref><ref>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 [http://www.pubmedcentral.nih.gov/picrender.fcgi?tool=pmcentrez&artid=1868096&blobtype=pdf PMID:1868096]</ref>
== Prevalence ==
Urticaria pigmentosa is an [[Rare disease|orphan disease]], affecting fewer than 200000 people in the [[United States]].
== 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.
== Symptoms ==
Urticaria Pigmentosa is characterized by excessive amounts of [[mast cell]]s 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).
== Irritants ==
The following can worsen the symptoms of urticaria pigmentosa:
# Emotional stress
# Physical stimuli such as heat, friction, and excessive exercise
# Bacterial toxins
# [[Venom (poison)|Venom]]
# Eye drops containing [[dextran]]
# [[NSAID]]s
# [[Alcoholic beverage|Alcohol]]
# [[Morphine]]
The classification of NSAIDs can be disputed. [[Aspirin]], for example, causes the mast cells to [[degranulation|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.
== Treatments ==
There are no permanent cures for urticaria pigmentosa. However, treatments are possible. Most treatments for [[Mastocytosis#Treatment|mastocytosis]] can be used to treat urticaria pigmentosa. Many common [[Antihistamine|anti-allergy medications]] are useful because they reduce the mast cell's ability to react to histamine.[http://dermnetnz.org/colour/urticaria-pigmentosum.html]
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.<ref name="pmid6491000">{{cite journal |author=Fairley JA, Pentland AP, Voorhees JJ |title=Urticaria pigmentosa responsive to nifedipine |journal=J. Am. Acad. Dermatol. |volume=11 |issue=4 Pt 2 |pages=740–3 |year=1984 |pmid=6491000 |doi=}}</ref> However, nifedipine has never been approved by the FDA for treatment of urticaria pigmentosa.
== See also ==
*[[Mastocytosis]]
*[[Mast cell|Mast Cells]]
*[[Urticaria]]
*[[Dermatographic urticaria]]
== References ==
<references/>
==External links==
* {{DermAtlas|27}}
*[http://www.bchealthguide.org/kbase/nord/nord192.htm BC Health Guide]
*[http://adam.about.com/encyclopedia/001466.htm About.com with Pictures]
*[http://www.wrongdiagnosis.com/c/cutaneous_mastocytosis/prevalence.htm Prevalence of Urticaria Pigmentosa]
*[http://www.aafp.org/afp/990600ap/3047.html AAFP]
*[http://www.skinsite.com/info_urticaria_pigmentosa.htm The Skin Site]
{{Congenital malformations and deformations of integument}}
[[Category:Rare diseases]]
[[Category:Dermatology]]