Purpura

Basics

Description

Skin lesions caused by extravasation of blood into the skin or subcutaneous tissue
Can be caused by fragile capillaries, poor dermal support, and/or platelet dysfunction
The resultant lesions do not blanch completely with pressure (as seen when pressing down through a glass slide)
Nomenclature varies by the size of the lesions:
- Petechiae (≤4 mm)
- Purpuric lesions (5–10 mm)
- Ecchymoses (>10 mm)
Color determined by depth and time of onset:
- Red if superficial and recent onset
- Purple if deep
- Deep purple, brown, orange, or blue-green with later presentations
Nonpalpable purpura:
- Simple hemorrhage or microvascular occlusion with ischemic hemorrhage
- Generally due to a platelet disorder:
  - Diminished production
  - Altered distribution
  - Increased destruction
  - Abnormal function
Palpable purpura:
- Generally due to vasculitis:
  - Autoimmune, small-vessel leukocytoclastic vasculitis
  - Hypersensitivity to various antigens
  - Formation of circulating immune complexes deposited in walls of postcapillary venules; activate complement that is chemotactic for polymorphonuclear leukocytes
  - Released enzymes damage vessel walls and cause leakage of blood
  - Vasculitic lesions may not be palpable in immunocompromised patients

Etiology

Nonpalpable purpura:
- Viral:
  - Echovirus
  - Coxsackie
  - Measles
  - Parvovirus B19
- Drugs:
  - Acetaminophen
  - Allopurinol
  - Anticoagulants
  - Aspirin
  - Corticosteroids
  - Digoxin
  - Furosemide
  - Gold salts
  - Lidocaine
  - Methyldopa
  - Nonsteroidal anti-inflammatory drugs
  - Penicillin G
  - Phenylbutazone
  - Quinidine
  - Quinine
  - Rifampin
  - Steroids
  - Sulfonamides
  - Thiazides
- Nutritional deficiencies:
  - Vitamin K deficiency
  - Vitamin C deficiency (scurvy)
- Bone marrow disease
- Hypersplenism
- Idiopathic thrombocytopenic purpura (ITP)
- Disseminated intravascular coagulation (DIC)
- Thrombotic thrombocytopenic purpura
- Liver or renal insufficiency
- Thrombocytopenia (<50,000 plt/cc)
- Thrombocytosis (>1,000,000 plt/cc)
- Spiking elevations of intravascular pressure (childbirth, vomiting, paroxysmal coughing)
- Hemophilia
- Solar purpura (only on sun-exposed areas)
- Posttransfusion
Palpable purpura:
- Viral:
  - Epstein–Barr virus
  - Cytomegalovirus
  - Hepatitis B
- Bacterial:
  - Streptococcal
  - Gonococcus
  - Meningococcus
  - Pseudomonas
  - Rickettsia rickettsii (Rocky Mountain spotted fever)
- Drugs:
  - Allopurinol
  - Anti-influenza vaccines
  - Cephalosporins
  - Gold
  - Heparin
  - Hydralazine
  - Iodides
  - Levamisole
  - Metoclopramide
  - Penicillin G
  - Phenylbutazone
  - Phenytoin
  - Quinidine
  - Quinine
  - Streptomycin
  - Sulfonamides
  - Thiazides
  - Ticlopidine
- Malignancies
- Autoimmune and connective tissue diseases. In immunocompromised hosts: Candida, Aspergillus
- Occlusion due to organisms living in vessels (generally immunocompromised hosts): Mucormycosis, aspergillosis, and disseminated strongyloidiasis
- Occlusion due to microvascular platelet plugs (heparin necrosis)
- Cold-related gelling or agglutination (cryoglobulinemia)
- Local or systemic coagulation abnormalities: Scarlet fever, Vibrio vulnificus bacteremia, “malignant chickenpox,” and “black measles” (both rare in the U.S.), coumadin necrosis
- Waldenstrom macroglobulinemia
- Protein C or S deficiency
- Wegener granulomatous
- Embolization: Cholesterol, crystal, thrombus (atrial myxoma, septic endocarditis, multiple myeloma)

Pediatric Considerations

Henoch–Schönlein purpura
Hemolytic uremic syndrome
Kawasaki disease
Neonatal:
- Extramedullary erythropoiesis in rubella and cytomegalovirus (blueberry muffin baby)
- Purpura fulminans (protein C and S deficiency)
- Maternal ITP
- Wiskott–Aldrich syndrome

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