Erythema Annulare Centrifugum

Synonyms - EAC, erythema gyratum perstans, erythema exudativum perstans, erythema marginatum perstans, erythema perstans, erythema figuratum perstans, erythema microgyratum perstans, erythema simplex gyratum.

It was first described by Darrier in 1916 and the aetiology and classification are still controversial. There seems to be both a superficial and a deep type and the term is often used to cover both.¹ It is a figurate or gyrate erythema believed commonly to be due to a hypersensitivity reaction to a possible wide range of stimuli. The condition can appear before other signs of disorder by up to 2 years.

• Drugs are implicated.² It is most commonly associated with antimalarials, cimetidine, spironolactone, gold, salicylates, piroxicam, penicillin, and amitriptyline.
• Infections of many types, including tuberculosis, Escherichia coli, dermatophyte fungi such as Trichophyton spp. tinea pedis, Pityrosporum orbiculare/Malassezia furfur are associated, Candida albicans and parasites including Ascaris lumbricoides. It has also been reported in association with Epstein-Barr virus (EBV).
• Food allergy, especially blue cheese and tomatoes
• Insect bites
• Malignancy, especially lymphoma
• It has been associated with thyroid overactivity
• It may be associated with pregnancy³
• Most often no cause is found

It is rare with an estimated incidence of 1 in 100,000 population per year. It can occur at any age and the sex incidence is equal. It is a reflection of its rarity that much of the literature is case reports rather than series or RCTs.

• The lesion may be asymptomatic or there may be pruritus
• There may be symptoms of underlying diseases such as Hodgkin's lymphoma or tuberculosis such as night sweats, fever, and chills
• It may predate the diagnosis of malignancy by 2 years or more, but it can also occur with or after the diagnosis
• A new drug may have been introduced

Skin

• The primary lesion begins as an erythematous papule that spreads peripherally while clearing centrally. These lesions enlarge at a rate of approximately 2 to 5 mm per day to produce annular, arcuate, figurate, circinate, or polycyclic plaques.
• The margin, which is usually indurated, varies in width from 4 to 6 mm, and, often, a trailing scale is present on the inner aspect of the advancing edge. The diameter of the polycyclic lesions varies from a few to several centimeters. There may be vesiculation.
• The lesions tend to be on the thighs or legs, but they may occur anywhere except the palms and the soles.
• The colour of lesions is pink to red with central clear areas. Occasionally, residual hyperpigmentation of dull red, brown, or violet is present.

Nails

The toe nails may show white bands.

Lymph Nodes

Lymphadenopathy may occur in association with infection, malignancy or autoimmune processes.

Thyroid

The thyroid should be palpated for enlargement or nodules as overactivity has been associated with the lesion.

Chest

Tuberculosis, lymphoma, sarcoidosis, and malignant bronchial carcinoid have been associated with the disease.

Abdomen

The abdomen should be examined for tenderness, masses, or hepatosplenomegaly. These may represent liver disease, lymphoma or even pregnancy has been associated with EAC.

Superficial fungal infections, systemic lupus erythematosus, sarcoidosis.⁴

• Examine a sample of skin in KOH for fungal hyphae.
• Tests are indicated to discover any underlying disorder such as infection or malignancy. They may include FBC, ESR, Chest X-ray.

• Exclude or treat any underlying disorder
• Withdraw or change any offending drug
• Topical steroids will alleviate symptoms but will not prevent the appearance of new lesions
• This is a rare condition that may imply a serious underlying disease. If in doubt, refer to a dermatologist.

There are usually no complication unless from an underlying disease.

If there is no underlying disease, the prognosis is excellent. It lasts on average 11 months but can be much shorter or recur over many years. It often resolves with effective treatment of any underlying disorder. If associated with pregnancy, it resolves soon after delivery.³