Expressions of progressive pigmented purpuric dermatitis
The clinical expressions of progressive pigmented purpuric dermatitis are varied but distinctive. At times, there are features in common grossly with leukocytoclastic vasculitis. A biopsy specimen can then be obtained in order to resolve the issue.
Histopathologically, the denominators common to all expressions of progressive pigmented purpuric dermatitis are an infiltrate of lymphocytes, extravasated erythrocytes, and, in time, siderophages. Earlier lesions contain more extravasated erythrocytes, whereas later ones show fewer extravasated red blood cells but more and more siderophages. The notion of “capillaritis” in progressive pigmented purpuric dermatitis is erroneous because no changes of vasculitis (fibrin within vessel walls and/or thrombi within lumen) are ever present.
The most common clinical presentation of pigmented purpuric dermatitis is Schamberg’s disease, which consists of pinpoint red to brown macules on the legs, usually bilaterally. Histopathologically, Schamberg’s disease is characterized by a superficial perivascular and interstitial infiltrate of lymphocytes accompanied by variable numbers of extravasated erythrocytes and siderophages (Fig. 1A). In lesions that have erupted, erythrocytes even may be found in the epidermis (as is the case, too, for acute lesions of other variants of progressive pigmented purpuric dermatitis and for acute lesions of all superficial perivascular dermatitides).
The eczematoid purpura of Ducas and Kapetanakis is not identifiable clinically, but is diagnosable histopathologically by virtue of changes indistinguishable from those of Schamberg’s disease with the addition of the presence of spongiosis focally (Fig. 1B). Clinically, the lesions resemble those of Schamberg’s disease.
The lesions of lichenoid purpura of Gougerot and Blum also are found most often on the legs, but also rarely on the trunk. They consist of red-brown papules and small plaques. Lichen aureus is one clinical variation of this condition in which lesions possess a distinctive golden hue because they are replete with siderophages. Histopathologically, lichenoid purpura of Gougerot and Blum shows a moderately dense bandlike infiltrate of lymphocytes that usually spares the dermo-epidermal junction (Fig. 1C). Extravasated erythrocytes and siderophages are present in variable numbers, depending on the duration of the lesion. In long-standing lesions, the altered papillary dermis is thickened and contains wiry collagen bundles like those found in long-standing patches and plaques of mycosis fungoides. The lymphoma, by contrast, usually lacks extravasated erythrocytes and siderophages.
Another clinical manifestation of persistent pigmented purpuric dermatitis consists of annular patches on the legs (purpura annularis telangiectoides of Majocchi). The histopathologic findings in this variant are indistinguishable from those in Schamberg’s disease and, on occasion, from those in the eczematoid purpura of Ducas and Kapetanakis. In sum, all of the variants of progressive pigmented purpuric dermatitis are dermatitis, unrelated to vasculitis of any kind and to lymphoma.
From the Institute. Reviewed by A. Bernard Ackerman, M.D. and Kenneth S. Resnik, M.D.