ISSN 2398-2977      

Dermatographism

pequis

Synonym(s): Pressure-induced urticaria, Dermographism, Dermatographia, Dermatographic urticaria, Urticaria factitia


Introduction

  • Cause: pressure applied to the skin. In some cases, certain foods may sensitize the skin’s reaction to pressure.
  • Signs: wheals or edema in areas of skin where an external source produced pressure, eg tack.
  • Diagnosis: history, typical clinical presentation, exclusion of differentials, confirmation “drawing” in the patient with a blunt object.
  • Treatment: avoidance of etiologic factors when possible. Standard treatment for urticaria, eg antihistamines, corticosteroids, fatty acids. Allergen specific immunotherapy.
  • Prognosis: favorable as general health is not usually compromised.

Pathogenesis

Etiology

  • The etiology is unknown, it can be associated with atopy Skin: atopy.
  • Pressure applied on skin evokes the reaction.
  • In some cases, some foods may trigger the reaction if administered before the pressure.
  • In humans, respiratory tract infections, hepatitis, diabetes mellitus, stress and drug reactions are associated with dermatographism.

Predisposing factors

General

  • Food reactions, drug reactions and environmental factors are thought to predispose the skin to this response.

Specific

  • Specific underlying factors can often be difficult to identify.

Pathophysiology

  • Cutaneous reaction following a suspected mechano-immunologic trigger.
  • Regardless of the cause, mast cell degranulation occurs. Sensitization by IgE is suspected in humans.
  • Basophils, macrophages and other cells release bioactive molecules, eg histamine, platelet-activating factor and prostaglandins.
  • Their effects include vascular smooth muscle relaxation and retraction of endothelial cells that result in plasma extravasation → edema (wheal).

Timecourse

  • Lesions appear within minutes following the exposure to pressure.
  • Delayed dermatographism reported in humans (not horses) when urticaria takes hours to develop.

Epidemiology

  • Urticarial reactions are usually specific to the individual.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • van den Brom-Spierenburg A J, Theelen M J P & Sloet van Oldruitenborgh-Oosterbaan M M (2019) Dermatographism in a horse, responsive to cetirizine treatment. Equine Vet Educ 31 (4), 191-194 VetMedResource.
  • Rashmir-Raven A M (2019) A review of physical urticarias in the horse. Equine Vet Educ 31 (4), 195-197 VetMedResource.
  • Pilsworth R C & Knottenbelt D (2007) Skin diseases refresher urticaria. Equine Vet Educ 19 (7), 368-369 WileyOnline.
  • Cornick J L & Brumbaugh G W (1989) Dermatographism in a horse. Cornell Vet 79, 109-116 PubMed.

Other sources of information

  • Fadok V A (2014) Equine Urticaria. In: Veterinary Allergy. Eds: Noli C, Foster A & Rosenkrantz W. Wiley Blackwell, UK. pp 338-343.
  • Scott D W & Miller W H Jr (2011) Skin Immune System and Allergic Skin Diseases. In: Equine Dermatology. 2nd edn. Saunders, USA. pp 263-313.
  • Knottenbelt D C (2009) Immune-Mediated/Allergic Diseases. In: Pascoe’s Principles and Practice of Equine Dermatology. 2nd edn. Saunders, USA. pp 253-297.

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