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Petechial spots over the back
Purpura (from the Latin, purpura, meaning "purple") is the appearance of red or purple discolorations on the skin that do not blanch on applying pressure. They are caused by bleeding underneath the skin. Purpura measure 0.3-1 cm, whereas petechiae measure less than 3 mm, and ecchymoses greater than 1 cm.[1]
This is common with typhus and can be present with meningitis caused by meningococcal meningitis or septicaemia. In particular, meningococcus, a Gram-negative diplococci organism, releases endotoxin when it lyses. Endotoxin activates the Hageman factor (clotting factor XII), which causes disseminated intravascular coagulation. The DIC is what appears as a rash on the affected individual.
[edit] Classification
Purpura is a common and nonspecific medical sign, however the underlying mechanism commonly involves one of the following:
There are also cases of psychogenic purpura described in the medical literature,[2] some claimed to be due to "autoerythrocyte sensitization." Other studies[3] suggest, that local (cutaneous) activity of tPA can be increased in psychogenic purpura, leading to substantial amounts of localized plasmin activity, rapid degradation of fibrin clots, and resultant bleeding. Petechial rash is also characteristic of a rickettsial infection.
[edit] See also
[edit] References
- ^ Mitchell RS; Kumar V; Robbins SL; Abbas AK; Fausto N (2007). Robbins basic pathology (8th ed.). Saunders/Elsevier. pp. 10–11. ISBN 1-4160-2973-7.
- ^ Anderson JE, DeGoff W, McNamara M (1999). "Autoerythrocyte sensitization (psychogenic purpura): a case report and review of the literature". Pediatric emergency care 15 (1): 47–8. PMID 10069314.
- ^ Lotti T, Benci M, Sarti MG, Teofoli P, Senesi C, Bonan P, et al. (1993). "Psychogenic purpura with abnormally increased tPA dependent cutaneous fibrinolytic activity". Int J Dermatol 32 (7): 521–3. doi:10.1111/j.1365-4362.1993.tb02840.x. PMID 8340191.
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