Dermatology
Purpura Mechanisms and Differential Diagnosis
Built from Dermatology, 5th Edition
What’s inside
14 sections · 76 slides
Overview
- What this topic covers
Approach to the Patient with Purpura
Sorting purpura by lesion number, distribution, and shape before naming a diagnosis
- Purpura: definition and scope
- Three mechanisms behind purpura
- Diagnostic approach by lesion pattern
- Distribution patterns: what each one suggests
- Multi-dependent pattern
- Clinical examples of petechiae and purpura
- Two families of purpura by shape
- Differential diagnosis of purpura by morphology
Retiform Purpura
A network-shaped bleed that marks blocked or inflamed small vessels
- What "retiform" means
- The shape of a retiform lesion
- Inflammatory vs non-inflammatory retiform purpura
- Vasculitic retiform lesions have their own signature
- The "many round, few retiform" pattern
- Retiform purpura with bullae in sepsis-associated DIC
Time Course of Purpuric Lesions
How a bruise fades, and why an aging lesion can mimic the wrong diagnosis
- Simple hemorrhage: a predictable fade
- Why timing matters for diagnosis
Macular Purpura: Differential Diagnosis
Petechiae, intermediate purpura, and ecchymoses, sorted by size
- The macular group is sorted by size alone
- Differential diagnosis of macular petechiae (≤4 mm in diameter).
- Differential diagnosis of intermediate macular purpura (5–9 mm).
- Differential diagnosis of macular ecchymoses (≥1 cm).
Palpable and Retiform Purpura: Differential Diagnosis
Raised or net-shaped lesions, split by inflammatory vs occlusive mechanism
- Palpable and retiform purpura: what sets this group apart
- Palpable purpura: inflammatory purpura with prominent early erythema.
- Palpable purpura: inflammatory purpura with prominent early erythema. (continued)
- Differential diagnosis of non-inflammatory retiform purpura.
- Differential diagnosis of non-inflammatory retiform purpura. (continued)
- Differential diagnosis of inflammatory retiform purpura.
Hemostasis and Coagulation
How the body stops bleeding, and how that system can misfire into purpura
- Primary hemostasis: the platelet plug
- Why low platelets cause petechiae, not bruises
- Secondary hemostasis: forming a clot
- Keeping clotting under control
- The brakes on clot formation
- The protein C pathway: critical for small vessels
- Clotting and inflammation overlap
Testing for Coagulation Problems
What a basic clotting work-up shows, and how to interpret it
- A basic clotting work-up
- Interpretation of prothrombin time (PT) and activated partial thromboplastin time (aPTT).
- Reading a prolonged clotting time
Antiplatelet and Anticoagulant Agents
Drugs that act on hemostasis, and how to reverse them
- Antiplatelet agents dermatologists use
- Anticoagulants: warfarin vs the newer agents
- Anticoagulants.
- Anticoagulants. (continued)
- Sites of action of anticoagulant medications
- Reversal agents in development
Selected Purpura Syndromes
Named syndromes not covered under microvascular occlusion or classic vasculitis
- Six syndromes covered in this section
- Pigmented purpuric dermatoses: overview
- Pigmented purpuric dermatoses: pathogenesis
- Types of pigmented purpuric dermatoses.
- Types of pigmented purpuric dermatoses. (continued)
- Schamberg disease vs venous hypertension
- Less common forms of pigmented purpuric eruptions
- Pigmented purpuric eruption: histopathologic features
- Pathology across the variants
- Schamberg disease with pinpoint petechiae
- Linear pigmented purpura
- Purpura annularis telangiectodes of Majocchi
- Purpura annularis telangiectodes of Majocchi, second example
- Capillaritis-like plaques in an elderly patient
- What else can look like pigmented purpura
- Treating pigmented purpuric dermatoses
Hypergammaglobulinemic Purpura of Waldenstrom
Recurrent macular vasculitis in a setting of high immunoglobulin levels
- Waldenstrom purpura: introduction
- What drives Waldenstrom purpura
- Clinical picture and disease course
- Diagnosis and treatment of Waldenstrom purpura
Other Selected Purpura Syndromes
Gardner-Diamond syndrome, paroxysmal finger hematoma, onyalai, and Mondor disease
- Gardner-Diamond syndrome
- Managing Gardner-Diamond syndrome
- Paroxysmal finger hematoma (Achenbach syndrome)
- Onyalai
- Mondor disease: introduction and cause
- Mondor disease: clinical picture and course
- Mondor disease: differential diagnosis and treatment
Summary
Pulling the pattern-based approach to purpura together
- Key takeaways
References
Source citations from the chapter
- References
- References (continued)
- References (continued)
- References (continued)
- Dermatology, 5th Edition (2-Volume Set)