Trunk rashes with central clearing

Trunk rashes with central clearing
Trunk rashes with central clearing

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A woman, aged 69 years, presented with a mildly pruritic rash on her buttocks and lower back that had appeared two weeks earlier. The woman, who had recently undergone a hip replacement, did not recall starting any new medication and had applied no topical medications to the affected area.

Examination of the skin revealed several oval-shaped plaques with a distinct erythematous rim and central clearing. In addition, a fine scale was present at the inner periphery. No other lesions were noted.


A woman, aged 26 years, noticed a slowly enlarging and itchy rash on her right flank. She denied taking any new medications and had not treated the rash with topical medications. History was remarkable only for hypothyroidism controlled with levothyroxine.

The patient had spent time outdoors on the New Jersey shore a few weeks earlier. No fever, malaise or flulike symptoms were reported. Physical exam revealed a 5-cm annular, slightly indurated and scaling rash with central clearing. There was no associated tenderness or warmth.

What is the diagnosis?

For CASE #1, click "NEXT." For CASE #2, click "3."

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.

CASE #2: Erythema migrans

Histopathologic finding of a dermal hypersensitivity reaction, along with the characteristic clinical appearance, confirmed the diagnosis of erythema migrans (EM).

Introduced in 1909, EM was described as an expanding ring-like lesion and thought to be the result of a bite of an Ixodes (deer) tick. Studies have correlated the rash of EM with early, localized Lyme disease, which is a systemic infection with the spirochete Borrelia burgdorferi.

Lyme disease is transmitted via an infected tick's salivary glands to the individual at the site of the inoculation. From there, the spirochete can either be eliminated by the host's immune system, remain localized at the site of the bite, or spread to surrounding and distant tissue.

EM is often referred to as the "bull's-eye rash" because of its clinical appearance. The rash typically starts as a red inflammatory papule that expands in a circular or oval shape over several days or weeks to an average size of 16 cm. Central clearing occurs simultaneously. At times, the primary papule or proximal redness remains, contributing to the "bulls-eye" or "target" appearance.

Several similar lesions can erupt elsewhere on the body. Although the lesions are usually macular, papular and scaly variations exist. The rash may be asymptomatic or cause mild itching or burning. Up to 50% of patients describe such mild flulike symptoms as malaise, poor appetite, and myalgia.

EM typically appears at the site of the tick bite but may start anywhere else on the body. The rash can appear one day to one month after a tick bite, with an average onset of seven to 14 days post-bite. EM typically persists for two to four weeks, and in some patients it recurs intermittently if left untreated. Unfortunately, many patients may have no evidence of the rash, and Lyme disease only presents in the later stages with extracutaneous manifestations.

Symptoms of Lyme disease result from both infection with the spirochete and from the body's immune responses to the infection. The multiple lesions of EM, when present, are most likely the results of the body's immune response.

Clinical manifestations are generally divided into three groups: early localized, early disseminated and chronic disseminated. EM is the primary manifestation of early-localized disease. (A detailed description of the symptoms of and treatment for disseminated disease is lengthy and beyond the scope of this article.)

While the classic appearance of the rash will assist in the diagnosis, it is important to consider the epidemiological context (i.e., geography, season and history of outdoor exposure). Further workup and monitoring is only indicated for those who exhibit extracutaneous manifestations and those who do not show prompt resolution of the rash with recommended treatment.

For the latter group, consider such alternative diagnoses as cellulitis or contact dermatitis, as well as co-infection with such other tick-borne illnesses as relapsing fever, tularemia, babesiosis, Rocky Mountain spotted fever and Colorado tick fever.4 Individuals presenting with an inflammatory erythematous papule at the inoculation site that appeared while the tick was still attached or within hours of the bite most likely do not have EM, but rather are showing a hypersensitivity reaction to the tick.

Patients presenting with EM and a positive history of exposure to a tick-infested area do not need serologic testing for a diagnosis of Lyme disease, and antibiotic therapy should be initiated. Empiric antibiotic therapy is also reasonable, even if the clinical diagnosis of EM is moderately probable and not certain. For other Lyme disease symptoms, such laboratory studies as B. burgdorferi antibody titers are necessary. Testing early in the course of Lyme disease is often still negative and may cause a dangerous delay in treatment.

EM generally responds and improves within a few days of starting antibiotic therapy. Controversy exists regarding optimum duration of treatment, with recommendations ranging from 10 to 30 days. Doxycycline 100 mg b.i.d. is the preferred drug for oral treatment in nonpregnant adults and children older than age 8 years. Amoxicillin 500 mg t.i.d. is the drug of choice for pregnant and pediatric patients.

Second-line drugs include erythromycin, azithromycin (Zithromax, Zmax), and cefuroxime (Ceftin) and are reserved for patient intolerant of first-line agents. With appropriate treatment, the prognosis for EM is excellent.

Early removal of ticks will lower the risk of contracting Lyme disease. Ticks need to be attached for at least 24 hours before disease transmission can occur. Individuals presenting with ticks that are not engorged do not need any treatment. Prophylactic treatment with a single dose of doxycycline 200 mg for nonpregnant adults and children older than age 8 years is recommended for such cases. Removal of the tick should be done carefully, using tweezers to grasp the tick close to the skin and pulling gently outward to detach.

Patients with EM should be educated regarding disease transmission as well as prevention strategies to avoid a repeat episode (e.g., cover exposed skin and tuck pants into the shoes when walking in wooded, brushy or grassy areas). Applying insect repellants containing DEET (N,N- diethyl-m-toluamide) will help repel ticks, however the American Academy of Pediatrics advises that children should not be exposed to products with greater than 10% concentration of DEET. Wearing light colored clothing will aid in identifying lingering insects. It is imperative to inspect the entire skin for evidence of ticks immediately after returning from outdoor exposures,5 paying special attention to body folds and the scalp. When a tick initially attaches to the human skin, it may be as small as a pinhead and difficult to see without a careful inspection. As the tick remains attached and feeds, it will become more engorged and more noticeable but may have already introduced infection by this time.

This patient was treated with doxycycline 100 mg b.i.d. for 14 days and reported resolution of the rash one week later. 

Esther Stern, NP-C, is a family nurse practitioner at Advanced Dermatology & Skin Surgery, P.C., in Lakewood, N.J.


1. Bressler GS, Jones RE Jr. "Erythema annulare centrifugum." J Am Acad Dermatol. 1981;4:597-602.

2. Weyers W, Diaz-Cascajo C, Weyers I. "Erythema annulare centrifugum: results of a clinicopathologic study of 73 patients." Am J Dermatopathol. 2003;25:451-462.

3. Kim KJ, Chang SE, Choi JH et al. "Clinicopathologic analysis of 66 cases of erythema annulare centrifugum." J Dermatol. 2002;29:61-67.

4. McGinley-Smith DE, Tsao SS. "Dermatoses from ticks." J Am Acad Dermatol. 2003;49:363-392.

5. Wormser GP, Dattwyler RJ, Shapiro ED et al. "The clinical assessment, treatment, and prevention of lyme disease, human granulocytic anaplasmosis and babesiosis: clinical practice guidelines by the Infectious Diseases Society of America." Clin Infect Dis. 2006;43:1089-1134.

All electronic documents accessed April 5, 2012.

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