Purpura

Purpura
Petechiae and purpura on the lower limb due to medication induced vasculitis
Classification and external resources
ICD-10	D69
ICD-9	287
DiseasesDB	25619
MedlinePlus	003232
MeSH	D011693

Purpura (from Latin: purpura, meaning "purple") are red or purple discolorations on the skin that do not blanch on applying pressure. They are caused by bleeding underneath the skin usually secondary to vasculitis or dietary deficiency of vitamin C (scurvy).^[1] Purpura measure 0.3–1 cm (3–10 mm), whereas petechiae measure less than 3 mm, and ecchymoses greater than 1 cm.^[2]

This is common with typhus and can be present with meningitis caused by meningococci or septicaemia. In particular, meningococcus (Neisseria meningitidis), a Gram-negative diplococcus organism, releases endotoxin when it lyses. Endotoxin activates the Hageman factor (clotting factor XII), which causes disseminated intravascular coagulation (DIC). The DIC is what appears as a rash on the affected individual.

Classification

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

• Platelet disorders (thrombocytopenic purpura)
  • Primary thrombocytopenic purpura
  • Secondary thrombocytopenic purpura
  • Post-transfusion purpura
• Vascular disorders (nonthrombocytopenic purpura)
  • 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
• Coagulation disorders
  • Disseminated intravascular coagulation (DIC)
  • Scurvy (vitamin C deficiency) - defect in collagen synthesis due to lack of hydroxylation of procollagen results in weakened capillary walls and cells
• Meningococcemia
• Cocaine use with concomitant use of the one-time chemotherapy drug and now veterinary deworming agent levamisole can cause purpura of the ears, face, trunk, or extremities, sometimes needing reconstructive surgery.^[3] Levamisole is purportedly a common cutting agent.
• Decomposition of blood vessels including purpura is a symptom of acute radiation poisoning in excess of 2 Grays of radiation exposure. This is an uncommon cause in general, but is commonly seen in victims of nuclear disaster.

Cases of psychogenic purpura are also described in the medical literature,^[4] some claimed to be due to "autoerythrocyte sensitization". Other studies^[5] suggest the local (cutaneous) activity of tissue plasminogen activator 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

• Bruise, which is a hematoma caused by trauma
• Petechia, which is a small type of hematoma (<3mm)
• Ecchymosis, which is a large type of hematoma (>1 cm)
• Purpura secondary to clotting disorders
• Purpura haemorrhagica in horses
• Pigmented purpuric dermatosis
• Schamberg disease (progressive pigmentary purpura)

References

1. ↑ "UCSF Purpura Module". 
2. ↑ 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. 
3. ↑ "Toxic Effects of Levamisole in a Cocaine User". New England Journal of Medicine. 
4. ↑ 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. doi:10.1097/00006565-199902000-00014. PMID 10069314. 
5. ↑ 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.  CS1 maint: Explicit use of et al. (link)

External links

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