Quiz 50: What is your diagnosis?

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Diagnosis: Quiz 50

Quiz 50

Answer: Leukocytoclastic vasculitis

Criteria for diagnosis clinically: Smooth-surfaced, rust-colored papules and plaques, some of them discrete and others having become confluent, are those of leukocytoclastic vasculitis.

Differential diagnosis clinically: Although this could, conceivably, be a manifestation of a persistent pigmented purpuric dermatitis (such as that of Gougerot-Blum), the most reasonable diagnosis, especially in the context of the site anatomic, is leukocytoclastic vasculitis. For purposes practical, the lichenoid purpura of Gougerot-Blum affects lower extremities, not upper ones.

Criteria for diagnosis histopathologically: A superficial and deep, perivascular and interstitial infiltrate made up mostly of neutrophils and many fragments of nuclei of neutrophils (nuclear "dust," leukocytoclasis) in conjunction with fibrin in the wall of numerous venules of the superficial plexus computes to a diagnosis of leukocytoclastic vasculitis.

Differential diagnosis histopathologically: There is none.

Clinicopathologic correlation: The papules are formed by the infiltrates of inflammatory cells and the edema in dermal papillae, the rust color is a consequence of erythrocytes extravasated in the upper part of the dermis, and the surface is smooth because the cornified layer is normal.

Options for therapy predicated on knowledge of histopathologic findings: Treatment of leukocytoclastic vasculitis, when widespread, is delivery systemic of corticosteroid, but also requisite concurrently must be an effort to determine the cause of the vasculitis, it ranging theoretically from a hypersensitivity reaction, to a particular drug, to a manifestation of a disease systemic, such as lupus erythematosus. In the case of the former, management requires interdiction of the drug, and of the latter, an effort to control the responsible underlying systemic process.

1) Leukocytoclastic vasculitis is a singular pattern morphologic in skin that is recognizable easily for what it is, clinically and histopathologically. The causes of leukocytoclastic vasculitis are many, just as is the case for suppurative infundibulitis and urticaria. When a distinctive pattern morphologic such as those just mentioned is identified, search must be undertaken for the cause of it.

2) In both urtica and leukocytoclastic vasculitis, neutrophils predominate in the infiltrate, but in the former there is no nuclear "dust," whereas in the latter, "nuclear dust" of neutrophils is a sine qua non for diagnosis with specificity. So-called urticarial vasculitis is nothing other than leukocytoclastic vasculitis at an edematous stage prior to extravasation of erythrocytes into the dermis; it is unrelated entirely to authentic urticaria. A distinction must be made between urticaria (constituted of actual hives) and urticarial (edematous papules that merely resemble those of urtica, such as the ones that develop in dermatitis herpetiformis, bullous pemphigoid, and in response to insect "bites," they being hive-like, not true hives). Edema is evident in the papillary dermis of those urticarial conditions (just as it is in this particular lesion of leukocytoclastic vasculitis), but no edema is spotted ever in the papillary dermis of a lesion of urtica.

3) A cliché loved by dermatologists, and especially by residents in dermatology, is "palpable purpura," it being employed as a synonym for leukocytoclastic (allergic) vasculitis. In fact, "palpable purpura" is as nonspecific as the ABCDEs (advocated uncritically for identification of both melanoma and the "dysplastic nevus"), "apple jelly nodules" (seen in conditions as disparate as lupus vulgaris and tubercloid leprosy), and "butterfly blush" (encountered in both lupus erythematosus and seborrheic dermatitis). In sum and in short, platitudes should be eschewed scrupulously if one wants to avoid becoming a cliché!

4) A pustule is apparent in the epidermis of this lesion of leukocytoclastic vasculitis. That is not unexpected; leukocytoclastic vasculitis may manifest itself clinically as pustules and vesicles, as well as urticarial papules, those three expressions of many tending to be purpuric. Each presentation clinical of leukocytoclastic vasculitis has a counterpart histopathologic that is distinctive equally.

5) Although lesions of leukocytoclastic vasculitis can occur anywhere on the skin, the site most favored is the leg. That is true, too, of all small-vessel vasculitides of different kinds, including septic and livedo, as well as large-vessel vasculitides, such as thrombophlebitis and arteritis (and for panniculitides of all types). The section of tissue shown here can be told to have come from a biopsy specimen taken of a lesion on a site other than the arm because in it are undeniable changes of stasis in the papillary dermis, namely, an increase in number of thick-walled capillaries lined by plump endothelial cells.

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