Is Schamberg's purpura blanchable?

Schamberg's Purpura and Blanchability

Schamberg's purpura is non-blanchable, as it represents extravasated red blood cells in the dermis that cannot be displaced by pressure. 1, 2

Clinical Characteristics of Schamberg's Purpura

• Schamberg's purpura (also called progressive pigmentary dermatosis) is characterized by red-yellow lesions with "cayenne-pepper" spots, primarily affecting the lower extremities 3
• The condition presents as non-blanchable purpuric macules that may have a characteristic "cayenne pepper" appearance 2
• The purpuric lesions result from extravasation of red blood cells into the dermis, making them non-blanchable when pressure is applied 1
• Unlike erythematous conditions caused by vasodilation, purpura represents actual hemorrhage into the skin that cannot be displaced by pressure 2

Histopathological Features

• Skin biopsy of Schamberg's purpura shows a superficial perivascular mononuclear inflammatory infiltrate with extravasation of red blood cells 3
• The histopathology confirms the presence of hemosiderin deposits and extravasated erythrocytes in the dermis, explaining the non-blanchable nature of the lesions 4
• Perivascular inflammation of dermal vessels is typically visible on H&E staining 4

Differential Diagnosis

• When examining purpuric lesions, it's important to distinguish between blanchable and non-blanchable lesions to aid diagnosis 2
• Blanchable lesions typically represent active vasodilation (as in erythema), while non-blanchable purpura indicates extravasated blood 1
• Other forms of purpura that are non-blanchable include thrombocytopenic purpura, vasculitic purpura, and embolic purpura 2

Clinical Assessment

• When evaluating purpuric lesions, applying pressure with a glass slide or transparent object (diascopy) can help determine if the lesion blanches 2
• The distribution pattern of purpuric lesions can provide diagnostic clues - Schamberg's purpura typically affects the lower extremities but can be more generalized 2
• Documentation of the date when the rash first appeared and its progression is recommended for all purpuric conditions 1

Management Considerations

• Schamberg's purpura is often chronic and can persist for years without treatment 3
• Various treatment options have been reported with variable success, including PUVA therapy 3, 5, narrowband UVB therapy 6, and fractional non-ablative laser 7
• Identifying and discontinuing potential causative medications is important, as drugs can trigger pigmented purpuric dermatoses 8

Key Pitfalls to Avoid

• Misinterpreting Schamberg's purpura as a drug-induced coagulopathy, especially in patients on anticoagulants 8
• Failing to perform diascopy to confirm the non-blanchable nature of the lesions 2
• Overlooking potential medication causes, such as amlodipine, which has been reported to trigger Schamberg's disease 8