What are the different morphological clinical forms of purpura and how do they relate to underlying diseases?

Different Morphological Clinical Forms of Purpura and Their Disease Associations

The morphological characteristics of purpura are critical diagnostic indicators that can help identify underlying diseases, with specific patterns often suggesting particular etiologies that guide clinical management.

Types of Purpuric Lesions and Their Morphological Characteristics

Palpable Purpura

• Characterized by raised, palpable hemorrhagic lesions that don't blanch with pressure 1
• Most commonly associated with leukocytoclastic vasculitis (LCV), which can be seen in:
  • ANCA-associated vasculitides
  • IgA vasculitis (formerly Henoch-Schönlein purpura)
  • Cryoglobulinemic vasculitis
  • Drug-induced vasculitis 1
• Histopathologically shows neutrophilic infiltrate with fibrinoid necrosis and nuclear fragmentation ("leukocytoclasia") 1

Non-palpable Purpura

• Flat, non-raised hemorrhagic lesions that don't blanch with pressure 2
• Often associated with:
  • Thrombocytopenia (as in idiopathic thrombocytopenic purpura)
  • Platelet dysfunction
  • Coagulation disorders 2

Petechial Purpura

• Pinpoint hemorrhagic lesions (<2mm) 2
• Common in:
  • Thrombocytopenia (platelet count <30,000) 3
  • Platelet function disorders
  • Early stages of some vasculitides 2

Ecchymotic Purpura

• Larger hemorrhagic patches (>2mm) 4
• Associated with:
  • Coagulation disorders
  • Severe thrombocytopenia
  • Vascular fragility disorders 4

Retiform Purpura

• Irregular, branching or stellate pattern of purpura 4
• Highly suggestive of:
  • Occlusive vasculopathies
  • Embolic phenomena
  • Antiphospholipid syndrome 3

Pigmented Purpura

• "Cayenne pepper"-like brown macules with petechiae 5
• Associated with:
  • Benign pigmented purpuric dermatoses (Schamberg's disease)
  • Cutaneous collagenous vasculopathy 5

Disease Associations Based on Purpura Morphology

Thrombocytopenic Purpura

• Characterized by non-palpable, often widespread petechiae and ecchymoses 3
• Key features:
  • Platelet count typically <30,000 3
  • Normal red and white blood cell morphology on peripheral smear 3
  • Absence of splenomegaly (splenomegaly suggests alternative diagnosis) 3
• Associated conditions:
  • Idiopathic thrombocytopenic purpura (ITP)
  • Drug-induced thrombocytopenia
  • Thrombotic thrombocytopenic purpura (TTP) 3

Vasculitic Purpura

• Typically palpable purpura, often symmetrically distributed on dependent areas 1
• May be accompanied by:
  • Systemic symptoms (fever, arthralgia)
  • Organ involvement (kidney, GI tract) 3
• Associated conditions:
  • IgA vasculitis (Henoch-Schönlein purpura) - characterized by palpable purpura, arthralgia, abdominal pain, and renal involvement 6
  • Mixed cryoglobulinemia syndrome - presents with the clinical triad of purpura, weakness, and arthralgias, along with low C4 complement 3
  • ANCA-associated vasculitides 1

Purpura in Mixed Cryoglobulinemia

• Typically presents as orthostatic purpura (appearing in dependent areas) 3
• Associated with:
  • HCV infection (in majority of cases)
  • Low complement C4 fraction
  • Cutaneous leukocytoclastic vasculitis 3
• May be part of a multisystem disorder affecting joints, kidneys, and peripheral nerves 3

Diagnostic Approach to Purpura

Initial Assessment

• Determine if purpura is palpable or non-palpable (fundamental first step) 1
• Assess distribution pattern (symmetric, dependent, retiform) 4
• Note associated symptoms (fever, joint pain, abdominal pain) 3, 6

Laboratory Evaluation

• Complete blood count with platelet count (essential first test) 2
• Peripheral blood smear examination 3
• Coagulation studies (prothrombin time, activated partial thromboplastin time) 2
• For suspected vasculitis:
  • Urinalysis (to detect renal involvement)
  • Autoantibodies (ANA, ANCA)
  • Complement levels
  • Hepatitis B and C testing 1

Histopathologic Evaluation

• Skin biopsy is essential for diagnosing vasculitic purpura 1
• Look for:
  • Leukocytoclastic vasculitis (neutrophilic infiltrate, nuclear dust, fibrinoid necrosis)
  • IgA deposits (in IgA vasculitis)
  • Vascular wall abnormalities 1

Special Considerations

• In HCV-positive patients, evaluate for mixed cryoglobulinemia syndrome 3
• In children with ITP, bone marrow examination is not routinely required unless there are atypical features 3
• In adults with suspected ITP, additional testing may include:
  • HIV testing
  • Helicobacter pylori testing
  • Antiphospholipid antibodies 3

Management Approach Based on Purpura Type

Thrombocytopenic Purpura

• For ITP with platelet counts >30,000 and minimal symptoms:
  • Observation without specific treatment is appropriate 3
• For ITP with platelet counts <20,000 and significant mucous membrane bleeding:
  • Treatment with IVIg or glucocorticoids 3
• For life-threatening bleeding:
  • Hospitalization
  • High-dose parenteral glucocorticoids
  • IVIg
  • Platelet transfusions 3

Vasculitic Purpura

• For skin-limited leukocytoclastic vasculitis:
  • Rest (avoiding standing or walking)
  • Low-dose corticosteroids
  • Colchicine 1
• For systemic vasculitis:
  • Higher doses of corticosteroids
  • Immunosuppressive agents based on organ involvement 1
• For drug-induced vasculitis:
  • Discontinuation of the culprit drug 1

Mixed Cryoglobulinemia Syndrome

• Comprehensive evaluation for HCV and other associated conditions 3
• Treatment directed at underlying cause (e.g., HCV therapy) 3
• Immunosuppression for severe organ involvement 3

Pitfalls and Caveats

• Splenomegaly is uncommon in ITP (<3% of cases) and should prompt consideration of alternative diagnoses 3
• Drug-induced thrombocytopenia must always be considered, with common culprits including quinidine, heparin, sulfonamides, and alcohol 3
• Pseudothrombocytopenia due to EDTA-induced platelet clumping occurs in about 0.1% of adults and should be ruled out by examining the peripheral blood smear 3
• The absence of serum cryoglobulins does not exclude mixed cryoglobulinemia syndrome; repeated testing may be necessary 3
• Purpura in children often represents benign, self-limited conditions, while in adults it more commonly indicates serious underlying disease 2