Overview

Erythema marginatum is a distinctive type of skin rash characterized by pink or red, non-itchy, ring-shaped lesions with clear central areas and slightly raised edges. It is most commonly associated with rheumatic fever, a complication that can arise after untreated or poorly treated streptococcal throat infections. Though relatively rare, erythema marginatum serves as an important clinical indicator, particularly in diagnosing acute rheumatic fever. The rash typically appears on the trunk and limbs, sparing the face, and may come and go over several days or weeks without leaving any scars.

Causes

The primary cause of erythema marginatum is the body’s autoimmune response following a Group A Streptococcus infection. It is most commonly linked to:

• Rheumatic Fever: Erythema marginatum is one of the major Jones criteria used for diagnosing acute rheumatic fever, a condition caused by an abnormal immune reaction to a streptococcal throat infection.
• Streptococcal Infections: Untreated strep throat or scarlet fever increases the risk of developing erythema marginatum as part of rheumatic fever.
• Other Rare Associations: Though rare, erythema marginatum has occasionally been linked with other autoimmune or inflammatory conditions, though its primary association remains with rheumatic fever.

Symptoms

The main symptom of erythema marginatum is the appearance of a characteristic rash, often accompanied by other symptoms of rheumatic fever:

• Rash Appearance: Pink or red circular lesions with a pale or normal-colored center and a raised, well-defined outer margin.
• Location: Typically found on the trunk, upper arms, and thighs, while sparing the face.
• Non-Itchy: The rash generally does not cause itching or discomfort.
• Transient Nature: Lesions may appear, fade, and reappear in different areas over several hours or days.
• Associated Rheumatic Fever Symptoms: May include joint pain (arthritis), fever, fatigue, heart inflammation (carditis), and sometimes involuntary movements (Sydenham chorea).

Diagnosis

Diagnosing erythema marginatum involves a thorough clinical evaluation, especially in the context of suspected rheumatic fever:

• Physical Examination: Identification of the characteristic rash pattern during a clinical examination.
• Jones Criteria: Erythema marginatum is classified as a major criterion in the Jones criteria for diagnosing acute rheumatic fever.
• Throat Swab Culture: Testing for Group A Streptococcus bacteria to confirm recent infection.
• Antistreptolysin O (ASO) Titer: A blood test to detect antibodies indicating a recent streptococcal infection.
• Echocardiogram: To assess for rheumatic heart disease or carditis if other rheumatic fever signs are present.
• Additional Blood Tests: Elevated inflammatory markers like ESR (erythrocyte sedimentation rate) and CRP (C-reactive protein) may support the diagnosis.

Treatment

The treatment of erythema marginatum focuses on addressing the underlying cause, primarily rheumatic fever, rather than the rash itself:

Antibiotics

• Penicillin: The first-line treatment for eradicating Group A Streptococcus infection and preventing recurrence of rheumatic fever.
• Alternative Antibiotics: For those allergic to penicillin, options include azithromycin or erythromycin.

Anti-Inflammatory Medications

• NSAIDs: Nonsteroidal anti-inflammatory drugs like aspirin or naproxen are used to manage joint pain and inflammation.
• Corticosteroids: In severe cases of carditis, corticosteroids may be prescribed to reduce heart inflammation.

Long-Term Prophylaxis

• Secondary Prophylaxis: Long-term antibiotics (usually monthly penicillin injections) are recommended to prevent recurrent rheumatic fever, especially in individuals with carditis.

Supportive Care

• Rest: Adequate rest is recommended during the acute phase to promote recovery.
• Monitoring: Regular follow-up is essential to monitor heart health and prevent complications.

Prognosis

The prognosis for erythema marginatum itself is generally favorable, as the rash typically resolves without leaving permanent marks or causing direct harm. However, since it is a marker of acute rheumatic fever, the overall prognosis depends on the severity and treatment of the underlying condition. Early diagnosis and prompt treatment of streptococcal infections significantly reduce the risk of rheumatic fever and its complications, including rheumatic heart disease.

With appropriate treatment and preventive care, most individuals recover fully from the initial illness. Long-term antibiotic prophylaxis is crucial to prevent recurrences and protect against heart-related complications associated with rheumatic fever.