What is erythema annulare?

Pathological reddening of the skin in a limited area is called erythema by dermatologists (from the Greek erythros – red), and annular erythema or annular (from the Latin annulus – ring) is not a disease, but a type of skin rash with pronounced focal hyperemia in the form of a ring. [ 1 ]

Epidemiology

As a rule, statistics on the occurrence of symptoms are not kept, so how often annular erythema appears is unknown.

However, it is known that with Lyme disease (after a tick bite), this type of erythema occurs in 70-80% of patients.

And in almost 70% of cases, annular erythema is a symptom of skin diseases, mainly fungal.

Approximately 10–20% of children with acute rheumatic fever develop erythema marginatum annulare.[ 2 ]

Causes What is erythema annulare?

Like other types of red spots on the skin of the body, red spots that have a ring-shaped form are symptoms of a number of conditions. Therefore, the term annular erythema syndrome combines both morphological variants of this type of rash and the accompanying manifestations, including itching, peeling, hyperkeratosis, etc.

Often, it is not possible to determine the specific causes of erythema annulare (or a specific trigger), but this does not mean that they do not exist. Such skin manifestations are often caused by infections.

If annular erythema from a mosquito bite, as well as some other insects, can only appear with increased human sensitivity, then annular erythema after a tick bite of the ixodid family, which transmits the spirochete Borrelia burgdorferi, is a pathognomonic skin symptom of Lyme disease (Lyme borreliosis).

Migratory annular erythema in borreliosis occurs a few days after the bite, has a rounded shape and quickly expands; the center of the hyperemic spot gradually becomes lighter, and there may be a point or papule at the site of the bite. At an early stage, symptoms of borreliosis are fever, general weakness, muscle and joint pain. Annular erythema and lymphadenopathy are also noted - an increase in regional lymph nodes.

Ring-shaped erythema appears on the face, body, legs and arms - in the form of smooth or scaly plaques with a light spot in the middle - with lupus vulgaris, that is, cutaneous tuberculosis, caused by Mycobacterium tuberculosis.

In secondary syphilis (caused by the spirochete Treponema pallidum), the appearance of Biett's anulare centrifugal erythema with hyperkeratosis along the edges of round spots is noted on the trunk, soles and palms of some patients.

Among viral infections, as causative factors for the appearance of red ring-shaped rashes, experts highlight the herpes virus type III (Varicella zoster virus), which leads to the development of herpes zoster, which is called shingles.

Infectious mononucleosis associated with herpes virus type IV (Epstein-Barr virus) manifests itself with symptoms such as swelling of the cervical lymph nodes, severe hyperemia of the pharynx, tonsillitis and annular erythema on the skin of the upper body, etc.

Skin reactions are also common in parasitic diseases. Thus, as a result of infection with flagellate parasites – trypanosomes (Trypanosoma cruzi), which are carried by triatomine bugs that bite people – annular erythema occurs in Chagas disease – American trypanosomiasis.

And, of course, chronic annular erythema can be associated with fungal diseases - dermatophytosis or dermatomycosis (for example, when affected by the fungus Trichophyton concentricum, Tinea pedis, Malassezia furfur). By the way, in adults, this is the most common cause of annular skin lesions.

But the etiology may not be related to infection. For example, annular erythema in SLE (systemic lupus erythematosus) most often occurs in cases of the subacute cutaneous form of this autoimmune disease - with the main localization on the trunk, in the thighs and buttocks. Details in the publication - Skin changes in lupus erythematosus.

Not everyone has annular erythema in rheumatoid arthritis, an autoimmune disease of connective tissue of an inflammatory nature. The affected areas include the skin of the trunk and limbs (from the inside), there is no itching.

In addition, erythema anulare may be iatrogenic, triggered by certain medications and vaccines.[ 3 ]

Risk factors

In addition to the diseases listed above, risk factors for the appearance of annular erythema include:

• sarcoidosis;
• hepatitis C, liver pathologies with cholestasis, biliary cirrhosis;
• diffuse toxic goiter leading to hyperthyroidism;
• Sjögren's syndrome;
• endocrine pathologies (primarily diabetes mellitus);
• oncological diseases (most often – lymphomas, leukemia, myeloma, tumors of the mammary, prostate or thymus glands);
• increased sensitivity of the body and/or tendency to allergic reactions;
• genetic predisposition;
• pregnancy.

Pathogenesis

Researchers consider the pathogenesis of this form of erythema as the development of a hypersensitivity reaction – cutaneous-vascular (with increased blood flow in the superficial capillaries of the skin), associated with an immune response to an antigen: in fungal and parasitic diseases, microbial and viral infections. [ 4 ]

An important role in the mechanism of the development of annular erythema is played by an increase in the level of eosinophils in the blood - eosinophilia.

Sometimes annular erythema is part of a paraneoplastic syndrome in oncology, and the main version of its pathogenesis is the effect of cytokines, tumor-associated macrophages and proangiogenic factors (in particular, vascular endothelial growth factor VEGF-A).

In patients with diabetes mellitus, simple annular erythema most likely occurs due to the accumulation of advanced glycation end products of proteins in tissues, which activate inflammatory reactions.

Idiopathic familial erythema annulare in infants is transmitted by genes - an autosomal dominant type of inheritance.

In pregnant women, annular erythema is explained by the same hormonal changes: an increase in the level of estrogen and progesterone in the blood.

From the histological side, with annular erythema, certain changes are observed in various layers of the skin: focal exudative inflammation and atrophy of epidermal cells (with disruption of the keratinization process), proliferation of Langerhans cells of the spinous layer, degeneration of cells of the basal layer, edema of the papillary layer. And in the tissues surrounding the skin capillaries - diffuse infiltrates of T-lymphocytes and eosinophils. [ 5 ]

Forms

There are several types of anular erythema.

• Erythema annulare rheumatica

It is distinguished separately according to the etiological principle.

• Erythema annulare migrans

It is considered chronic, is compared with manifestations of dermatological diseases of various genesis and in many cases is associated with infections and oncology. In particular, such erythema occurs with Lyme borreliosis.

• Erythema annulare centrifugum

Synonyms: annular erythema Darier, annular marginal erythema. The first signs appear as a small pink papule, which gradually increases to a hyperemic spot (or thin plaque) of a round or oval shape. The increase occurs centrifugally - from the middle to the edges, which on the inside may be covered with scales of exfoliated skin. At the same time, the redness in the center gradually decreases and disappears.

• Erythema multiforme annulare

These are non-itchy, sharply defined hyperemic spots that gradually increase in size to form plaques. The central part of the erythema clears or changes structure and color.

In addition, some experts distinguish: necrolytic migratory erythema annulare (with the formation of blisters, which after their resolution are covered with a scab) and persistent paraneoplastic - in oncological diseases.

Annular erythema in children

In infancy, annular erythema is rare, and, as practice shows, the most common at this age is idiopathic annular erythema. [ 6 ]

Parvovirus B19 (family Parvoviridae, genus Erythroparvovirus) that affects children causes not only the usual erythema on the cheeks; within one to two weeks, so-called Chamer's erythema annulare may appear on the trunk and limbs, in which the central part of the rash elements gradually begins to fade. After a few weeks, it spontaneously disappears, but during the first year of the child's life it can recur - without any consequences. [ 7 ]

As a complication after streptococcal tonsillitis or inflammation of the pharynx in children and adolescents, annular erythema may appear in rheumatic fever - one of its main signs associated with the activation of inflammation of the joints or heart muscle. For more details, see - Rheumatic fever.

In this case, the ring-shaped erythematous plaques with a clear center that do not cause any sensations quickly increase in size and quickly disappear, but repeated outbreaks are possible.

It is also important to keep in mind such equally serious diagnostic options as neonatal lupus erythematosus, herpes zoster in children, and juvenile rheumatoid arthritis. [ 8 ]

Complications and consequences

In some cases, annular erythema disappears spontaneously (sometimes with periodic relapses), in others, if the infection is severe or the disease is systemic, consequences and/or complications arise.

Thus, in late-stage Lyme borreliosis, erythema leads to chronic atrophic acrodermatitis, affecting the outer surfaces of the upper and lower extremities.

If erythema causes severe itching, then scratched skin may become secondary infected, leading to inflammation. [ 9 ]

Diagnostics What is erythema annulare?

Although at least half of cases of red, ring-shaped skin rashes are still considered idiopathic, diagnosis begins with a visual examination, a review of the patient's medical history (including all medications and recent vaccinations), and a skin examination.

For laboratory tests, blood tests are taken: general clinical and detailed, for rheumatoid factor, ELISA for antibodies (to viruses, tuberculosis mycobacteria, streptococcus), for the C3 component of complement in the blood, for eosinophils, for thyroid-stimulating hormones. General urine and feces tests are also taken. Allergy tests may be required.

To rule out a fungal infection, a skin scraping is performed, and a skin biopsy and histological examination may be required to confirm the diagnosis.

Instrumental diagnostics may be limited to dermatoscopy.

Differential diagnosis

Annular erythema is a non-specific symptom, therefore the tasks that differential diagnostics must solve are to verify the causal factors and differentiate other morphological types of rashes, for example, in granulomatous and atopic dermatitis and dermatomycosis, vulgar (plaque) psoriasis, mastocytosis, erysipelas, etc. [ 10 ]

Treatment What is erythema annulare?

Once the disease that caused the appearance of annular erythema is identified, the main treatment is aimed at it.

If this symptom is associated with the third type of herpes virus, treatment for shingles is necessary.

In severe rheumatoid arthritis in patients over 18 years of age, Etanercept (Enbrel) can be used, which is administered subcutaneously. This drug is prescribed with caution and only in the absence of acute and chronic infections. The list of its side effects includes: the development of infectious inflammations of various localizations and skin manifestations; negative effects on the nervous, cardiovascular and urinary systems and the gastrointestinal tract.

Read also – Treatment of rheumatoid arthritis

Dermatomycosis can be treated with topical agents - effective antifungal ointments.

There are also medications to relieve itching: antihistamines taken orally or topical anti-itch ointments.

Local therapy traditionally uses ointments of various compositions for skin rashes, and in many cases these are ointments and creams with corticosteroids. However, non-hormonal agents are also recommended: Protopic ointment (with tacrolimus) or Elidel cream (with pimecrolimus).

In the absence of fungal diseases, systemic corticosteroids can be prescribed: Methylprednisolone, Betaspan (Betamethasone, Diprospan), etc., the appropriateness and regimen of use of which with the exact dosage is determined exclusively by the attending physician.

Can antibiotics be used for erythema annulare? Treatment with antibacterial drugs against streptococcal infection is carried out for rheumatic fever, for more details see - Treatment of streptococcal infection.

Antibiotics are also used after a tick bite. And in cases of annular erythema in American trypanosomiasis, the disease itself is treated with antimicrobial agents based on nitrofuran derivatives, which include Nifurtimox. The drug is contraindicated in cases of kidney and liver problems, and the side effects it causes can include nausea and vomiting, dizziness and headache. [ 11 ]

Prevention

There are no measures to prevent the appearance of this symptom.

Forecast

Even when the cause of erythema anulare is not determined, it may resolve spontaneously.

In other cases, this symptom is present for quite a long time - from three months to a year or more, but in itself it does not affect the prognosis of the outcome of the disease. However, possible relapses of skin manifestations of chronic diseases negatively affect the general well-being and reduce the quality of life.