purpura

Purpura
Classification and external resources
ICD-10	D69.
ICD-9	287
DiseasesDB	25619
MeSH	D011693

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.

Classification

Purpura is a common and nonspecific medical sign, however the underlying mechanism commonly involves one of the following:

• Platelet disorders
  • Primary thrombocytopenic purpura
  • Secondary thrombocytopenic purpura
  • Post-transfusion purpura
• Vascular disorders
  • Microvascular injury, as seen in senile (old age) purpura, when blood vessels are more easily damaged
  • Hypertensive states
  • Deficient vascular support
  • Vasculitis, as in the case of Henoch-Schönlein purpura or[?] Hepatitis C
• Coagulation disorders
  • Disseminated intravascular coagulation (DIC)
  • Scurvy (vitamin C deficiency) - defect in collagen synthesis due to lack of hydroxylation of procollagen. It results in weakened capillary walls.

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.

See also

• Petechia
• Ecchymoses
• Purpura secondary to clotting disorders
• Food-induced purpura

References

1. ^ 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. 
2. ^ 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. 
3. ^ 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. 

External links

• Evaluating the Child with Purpura from American Academy of Family Physicians