Diagnostic Considerations
Pigmented purpuric dermatoses must be distinguished from early cutaneous T-cell lymphoma, purpuric clothing dermatitis, stasis pigmentation, scurvy, leukocytoclastic vasculitis, purpuric generalized lichen nitidus, [7] and drug hypersensitivity reactions (eg, allergy to rituximab, carbamazepine, meprobamate, bufexamac, chlordiazepoxide, furosemide, nitroglycerin, vitamin B-1, or injection with medroxyprogesterone acetate). [8, 9, 10, 11, 12, 13, 14]
A case of glipizide-induced pigmented purpuric dermatosis has been reported. [15]
Topical fluorouracil and eutectic mixture of local anesthetics (EMLA) have been implicated in a pigmented purpuric dermatitislike skin eruption.
Pharmacologically induced regressed Kaposi sarcoma lesions may be misdiagnosed clinically and histologically as pigmented purpuric dermatitis. [16]
Buckthal-McCuin and Mutasim described macular arteritis mimicking pigmented purpuric dermatosis. [17]
Differential Diagnoses
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Vasculitis
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Pigmented purpuric dermatitis affecting the trunk. Some of the lesions show the characteristic orange-brown, speckled, cayenne pepper–like discoloration that is the hallmark clinical sign of a capillaritis. Men are more frequently affected than women. If the lesions are pruritic, then the term itching purpura is sometimes used. Early cutaneous T-cell lymphoma, purpuric clothing contact dermatitis, and drug hypersensitivity reactions should be considered in the differential diagnosis.
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Lichen aureus is the name given to localized pigmented purpuric dermatitis or capillaritis. In this patient, the skin on the extensor surface of the elbow is affected.
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Histologic features of a skin biopsy sample obtained from a patient with lichen aureus shows extravasation of erythrocytes and a perivascular T-cell infiltrate.
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Endothelial cell swelling is a histologic feature of capillaritis. This biopsy sample was obtained from a patient with lichen aureus.
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Hemosiderin deposition is seen in dermal macrophages in this biopsy sample obtained from a patient with lichen aureus.
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Capillaritis affecting the lower legs is known as Schamberg disease. In Schamberg disease, irregular plaques and patches of orange-brown pigmentation develop on the lower limbs.
