Trunk rashes with central clearing

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Trunk rashes with central clearing
Trunk rashes with central clearing

CASE #1: Erythema annulare centrifugum

Although it is the most prevalent of the figurate or gyrate erythemas, erythema annulare centrifugum (EAC) is a rare condition. The gyrate erythemas represent a group of rashes that are believed to be a cutaneous response to several agents, including medications, infection, systemic malignancy and stress.

These rashes can be classified as a superficial or deep gyrate erythema.1 There is much controversy in the literature regarding classification, but the common presentation of EAC is typically classified as a superficial gyrate erythema.2

EAC presents with several erythematous annular, polycyclic or oval lesions that slowly enlarge centrifugally at an estimated rate of 2 mm to 4 mm per day. The lesions simultaneously clear centrally. The characteristic sign and diagnostic clue of EAC is a faint trailing scale present at the inner periphery of the lesions. Occasionally, particularly in the deep form of EAC, the scale is not present. EAC typically appears on the trunk and extremities, with greatest incidence on the thighs. The palms, soles, and mucus membranes are usually spared.

Middle-aged adults are most often affected, but EAC has been described in neonates and children, too. There does not appear to be any racial or sex preference. 

The pathogenesis of EAC remains unknown, but an increasing number of studies supports the theory of EAC representing a hypersensitivity reaction to a variety of causes. Although many cases are idiopathic, underlying causes must be ruled out. A concurrent dermatophytosis is likely the most common etiology. One study that found 48% of patients with EAC had an associated cutaneous fungal infection.3 Tinea pedis is the most common of the dermatophytoses.

Such medications as penicillin, finasteride (Propecia, Proscar), hydroxychloroquine (Plaquenil, Quineprox), amitriptyline (Elavil, Endep, Vanatrip) and spironolactone (Aldactone) have been implicated. When associated with medications, EAC typically appears within a few weeks of starting the prescription.

Herpes zoster and HIV infection are also reported to occur with EAC. Ingestion of molds and tomatoes has been reported as a possible etiology as well. Systemic diseases associated with EAC include hepatic disease, lupus, thyroid disorder and Sjogren's syndrome. EAC may occur in pregnancy and subsequently resolve postpartum. Underlying malignancy has been reported to trigger EAC and must be investigated and ruled out. 

In most studies, a causal relationship is rarely established, primarily because the temporal relationship between EAC and the underlying disorder is variable, with EAC appearing before, during or after diagnosis. With malignancy, however, the course of EAC tends to parallel that of the underlying cancer, with rash resolution occurring with tumor suppression and recurring with relapse. 

The differential diagnosis of EAC includes subacute cutaneous lupus, discoid lupus, erythema migrans, pityriasis rosea, tinea corporis and erythema multiforme.

A skin punch biopsy is often performed to confirm the diagnosis. In the superficial type of EAC, a nonspecific perivascular lymphohistiocytic infiltrate is seen around the dermal vasculature in a tight "coat sleeve" pattern, along with papillary dermal edema. Epidermal changes of parakeratosis and spongiosis are often seen.

A thorough physical exam should be performed. Laboratory workup should be done based on the exam findings. An extensive workup searching for malignancy is unnecessary, given that the association with EAC is not definite. Very often, no cause is identified, and the rash resolves spontaneously.

EAC is mostly self-limiting, with a mean duration of 11 months and a range of duration from four weeks to 34 years. For many patients, however, EAC may be a chronic and relapsing disorder. Treatment must be directed at the underlying cause (if discernible). A topical medium potency steroid, such as triamcinolone acetonide 0.1%, may be prescribed for localized pruritus. Although this cream may lead to resolution of the treated lesions, it does not prevent the appearance of new lesions. If pruritus is severe, a short course of oral prednisone may be prescribed. Case reports have shown success with treatment with calcipotriol, hyaluronic acid, metronidazole and etanercept (Enbrel). 

The patient in this case underwent a skin biopsy, which confirmed the diagnosis of EAC. She was referred to her internist for a complete physical exam and routine, age-appropriate labwork. The rash resolved spontaneously within approximately six months. Although no underlying cause was definitively indentified, consideration was given to a new medication given during hospitalization for her hip surgery.

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