Quiz 23: What is your diagnosis?

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Diagnosis: Quiz 23

Quiz 23

Answer: Nummular dermatitis

Criteria for diagnosis histopathologically: The constellation of a moderately dense superficial perivascular infiltrate of lymphocytes joined by eosinophils, edema of the papillary dermis, spongiosis in loci of an unevenly hyperplastic epidermis, and scale-crust tallies to a diagnosis of nummular dermatitis.

Differential diagnosis histopathologically: Changes identical to those shown in these photomicrographs may be encountered in allergic contact dermatitis. In an id reaction, in contrast, the infiltrate of inflammatory cells is not as dense and in dyshidrotic dermatitis. In contradistinction, the stratum corneum is that of a palm or sole, or of a site very near it. A response to a "bite" of an insect tends to be associated with an infiltrate, wedge-shaped and both superficial and deep, in which many eosinophils are scattered in the interstitium of the reticular dermis in addition to their being huddled around venules in conjunction with lymphocytes usually preponderant there.

Criteria for diagnosis clinically: Pink papules, some of them topped by a subtle scale-crust and, in loci, arranged in a cluster, some of the papules having become confluent, is consonant with nummular dermatitis. Note on the legs that several coin-shaped lesions are made up of similar papules, an appearance typical of nummular dermatitis.

Differential diagnosis clinically: In the context of all the lesions visualizable, there is none. 

Clinicopathologic correlation: A papule came into being by virtue of the infiltrate of inflammatory cells coupled with edema in the papillary dermis and, to a lesser extent, hyperplasia of the epidermis. The redness resulted from dilation wide of venules of the superficial plexus and, especially, capillaries in edematous dermal papillae, they, in vivo, having been filled with erythrocytes. The hint of scale-crust is an expression of elongate mounds of parakeratosis that house serum.

Options for therapy predicated on knowledge of histopathologic findings: Options for therapy predicated on knowledge of histopathologic findings

1) Although the lesions pictured clinically "close-up" could be intuited to be those of nummular dermatitis by virtue of what could be construed to be an incipient coin-shaped plaque, the diagnosis is fortified by inspection gross of lesions on the legs that have assumed the shape of coins of different sizes. The diagnosis is established firmly by correlation of features clinical with findings histopathologic, to wit, papules in proximity close to one another, forming plaques in the shape of a coin in conjunction with a spongiotic psoriasiform dermatitis that houses some eosinophils in addition to lymphocytes.

2) The changes captured in the photomicrographs in this section of tissue from a biopsy specimen taken of a papule in this patient with nummular dermatitis are indistinguishable from those of allergic contact dermatitis. Although clinically the two conditions are very different from one another, the fact that individual papules, papulovesicles, and vesicles of both conditions cannot be distinguished from one another and, moreover, that the findings histopathologic in them are the same raises the possibility that nummular dermatitis is related pathogenetically to allergic contact dermatitis. Sometimes attributes clinical of both allergic contact dermatitis and nummular dermatitis appear together in a single patient. Unlike the situation in allergic contact dermatitis, however, the cause of nummular dermatitis is not known.

3) An individual papule of nummular dermatitis shown here cannot be told apart not only from one of allergic contact dermatitis, but also from a solitary papule of an id reaction. In some instances, the findings histopathologic in an id reaction are indistinguishable from those of nummular dermatitis and of allergic contact dermatitis. Practically never, however, is the infiltrate of inflammatory cells in an id reaction as dense as it is in this example of nummular dermatitis. Moreover, the spongiosis in all three conditions may eventuate in spongiotic vesicles that can be appreciated clinically as overt blisters. Last, in regard to individual lesions clinical and alterations histopathologic, dyshidrotic dermatitis is indistinguishable from allergic contact dermatitis, nummular dermatitis, and an id reaction. In dyshidrotic dermatitis, lesions develop invariably on, or very close to, volar skin, whereas that is not the usual case for nummular dermatitis. When nummular dermatitis, allergic contact dermatitis, and id reactions do develop on volar skin, they cannot be told apart histopathologically from dyshidrotic dermatitis. In instances rare, all four "entities" clinical may be manifest concurrently in the same patient, that again suggesting an association pathogenetic of them.

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