What is Erythema Marginatum?
Erythema marginatum is a skin reaction caused by inflammation. It is most often noticed during an episode of acute rheumatic fever. Although it’s uncommon, it’s extremely valuable in diagnosing conditions like acute rheumatic fever and a few other rare diseases. The rash can be described as transient (meaning it comes and goes), able to turn white when pressure is applied, doesn’t itch, and is characterized by flat, discolored areas. The rash is usually on the trunk (the body excluding the head, neck, and limbs) and limbs. It can also occur in rare genetic conditions such as hereditary angioedema and an infectious disease known as psittacosis.
What Causes Erythema Marginatum?
Erythema marginatum is often linked to certain conditions like acute or chronic rheumatic fever, psittacosis, and C1esterase inhibitor deficiency, which is also known as hereditary angioedema. Acute rheumatic fever is mainly connected with an infection caused by a group of bacteria known as beta-hemolytic streptococcus. But, it has also been found with another bacteria group called group C streptococcus.
Two specific types of group A beta-hemolytic streptococcus, known as M3 and M18, which are associated with acute rheumatic fever, have been connected with the creation of antibodies against a component of our body called collagen IV. These antibodies are believed to lead to a condition known as post-streptococcal rheumatic disease, which occurs after a streptococcus infection.
However, how these antibodies are formed is not clearly understood. But, a theory called molecular mimicry has been proposed as a probable explanation, especially applicable in the case of acute rheumatic fever. According to this theory, our body’s immune system is fooled into attacking healthy cells, mistaking them for harmful invaders, due to their similar appearance.
Risk Factors and Frequency for Erythema Marginatum
Erythema marginatum, a condition connected to acute rheumatic fever, doesn’t favor any particular sex. It is more frequently seen in children aged 5 to 15 years old rather than adults. However, it’s worth noting that only a small percentage of individuals with acute rheumatic fever (about 6%) have been reported to have Erythema marginatum.
Signs and Symptoms of Erythema Marginatum
Acute rheumatic fever typically affects children between the ages of 5 and 15. After a sore throat caused by the streptococcus bacteria, it takes about 2 to 5 weeks for heart inflammation to start. A rash known as erythema marginatum could occur before, during, or after heart inflames. This rash can also appear in patients with chronic heart inflammation.
The rash usually starts as a painless red spot that grows outward and merges with other spots to form ring-like or snake-like patches. These patches appear in groups over days to weeks and are temporary. The spots move at a speed of 2 to 12 mm over several hours.
The spots usually become more noticeable when exposed to heat and fade away leaving a slight discoloration without any thinning or flaking of the skin. The rash is most common on the torso, armpits, and the upper part of the arms and legs, while the face is typically spared. The rash may last from a few hours to a few weeks and is often more visible in the afternoon.
Testing for Erythema Marginatum
Erythema marginatum is a type of skin rash that is diagnosed by visually assessing the red, ring-like patches on the skin. Identifying this rash can lead to diagnosing diseases like acute rheumatic fever, a serious disease that can result from untreated strep throat or scarlet fever.
Diagnosis of acute rheumatic fever relies on a set of criteria known as the Jones criteria. These are divided into major and minor factors.
The major factors include:
- Polyarthritis: Inflammation and pain in many joints.
- Sydenham’s chorea: A disorder characterized by rapid, uncoordinated, jerking movements.
- Clinical and subclinical carditis: Obvious or subtle inflammation of the heart muscle.
- Erythema marginatum: The aforementioned skin rash.
- Subcutaneous nodules: Lumps under the skin.
The minor factors are:
- Fever above 38 Celsius (100.4 Fahrenheit).
- Polyarthralgia: Pain in multiple joints.
- High levels of inflammation markers such as ESR (erythrocyte sedimentation rate) and CRP (C-reactive protein).
- Prolonged PR interval: A specific pattern seen on an electrocardiogram (a test that measures the electrical activity of the heart).
For a diagnosis of acute rheumatic fever, you must have either two major factors or one major factor plus two minor factors. In addition, there should be evidence of a recent strep infection, detected by a high anti-Streptolysin O titer (a blood test that measures antibodies against streptococcal bacteria) or a throat swab culture positive for group A streptococcus (the bacteria that cause strep throat).
Besides these criteria, other lab tests might be performed, such as a complete blood count, or an echocardiography which uses sound waves to create a picture of the heart. When erythema marginatum is associated with hereditary angioedema, a genetic disorder that causes swelling, tests for specific proteins in the blood could also be performed.
In the case of psittacosis, a rare infectious disease often transmitted by infected birds, its diagnosis might rely on the detection of chlamydia psittaci bacteria in respiratory samples or evidence of an immune response against this bacteria in the blood.
Lastly, a skin biopsy—a test that involves taking a small sample of skin for examination under a microscope—can provide additional insights. In erythema marginatum, the biopsy typically shows inflammation around blood vessels and red blood cells leaking out of the blood vessels, though this finding can vary from person to person.
Treatment Options for Erythema Marginatum
There isn’t a specific treatment for this skin condition because it goes away on its own. Even if you treat the related rheumatic fever, the skin rash will still go through its normal course.
For people with a genetic condition called hereditary angioedema, conventional treatment involves the use of fresh frozen plasma, a blood product, during flares of the condition as well as for prevention. New treatments like icatibant and ecallantide are now available, but these medicines only work during an acute attack. A strategy that has shown promise is to use plasma-derived or recombinant C1 esterase inhibitor, a protein from the blood, when the very first signs of the skin rash appear.
Doxycycline, a type of antibiotic, is considered the top choice for treating an infection called psittacosis. It’s usually taken every 12 hours for 2 weeks. However, if a person can’t take tetracyclines like doxycycline, alternatives might include antibiotics from the macrolide class, like azithromycin, or fluoroquinolones as a third option.
What else can Erythema Marginatum be?
Erythemas—redness on the skin caused by increased blood flow in the capillaries—are diagnosed using a combination of clinical examination and laboratory tests.
For a clinical condition known as erythema marginatum, there are several possible diagnoses, including:
- Annular urticaria
- Annular erythema of infancy
- Erythema annulare centrifuged (EAC)
- Autoinflammatory diseases like TNF receptor-associated periodic syndrome and Still disease
- Erythema multiforme
- Erythema marginatum hemorrhagicum—a type of erythema with bleeding and the formation of crusts, usually seen in patients taking a medication called sorafenib
From a laboratory perspective, figurate erythemas (erythemas with particular shapes and patterns) can be identified by examining the type of inflammation present in skin samples. This includes the presence of:
- Lymphocytes
- Neutrophils and eosinophils
- Granulomas (collections of immune cells)
- Plasma cells
Each type of inflammation is associated with certain conditions. For example, inflammation with neutrophils and eosinophils is seen in conditions like annular psoriasis and urticaria multiforme. In contrast, lymphocyte inflammation is characteristic of erythema annulare centrifugum, chronic erythema migrans, among others.
The presence of granulomas is a key feature of conditions like granuloma annulare, sarcoidosis, and borderline tuberculoid leprosy. Additionally, syphilis, which is sometimes called the “great mimicker” due to its varied skin presentations, is often diagnosed by the presence of lymphocytes, plasma cells, and a skin change called lichenoid interface dermatitis.
Apart from these observations, specialized staining techniques can be used to identify certain organisms or to detect immune reactions in the skin. For example, silver staining can be used to detect spirochetes in skin affected by secondary syphilis and erythema migrans. In some cases, the substances present in the skin can suggest a link with another condition. For instance, with erythema marginatum linked with hereditary angioedema, a substance called bradykinin is often found in the skin.
What to expect with Erythema Marginatum
The skin changes, known as erythema marginatum, often resolve on their own and can come and go or stick around for a few days during or after an outbreak of acute rheumatic fever. Acute rheumatic fever is a disease that can develop as a complication of untreated strep throat or scarlet fever. Erythema marginatum is a rash that is often associated with this condition.
Possible Complications When Diagnosed with Erythema Marginatum
The skin lesions caused by erythema marginatum generally have a straightforward progression. However, these could signal the beginning of heart inflammation in patients with sudden onset rheumatic fever. Unfortunately, a small percentage of these patients could also develop rheumatic heart disease.
Key Points:
- Erythema marginatum causes skin lesions
- These skin lesions can signal the start of heart inflammation in cases of sudden rheumatic fever
- A small percentage of patients can progress to rheumatic heart disease
Preventing Erythema Marginatum
The best way to prevent acute rheumatic fever, a severe form of strep throat, is to avoid living in overcrowded conditions, as this has been found to be the most significant risk factor. However, this isn’t a practical solution, especially in developing countries, because the costs outweigh the benefits.
Most people with rheumatic heart disease, a complication of acute rheumatic fever, have previously experienced a severe sore throat that was either untreated or unnoticed. Therefore, in regions where this disease is prevalent, it’s advised for individuals and their caregivers to seek medical advice if symptoms such as fever, a sore throat, a rash, or joint pain develop.
