Erythema nodosum is a condition where red lumps appear across the patient’s shins. Erythema means red and nodosum directly translates from Latin as “knots”, referring to lumps.
It is caused by inflammation of the subcutaneous fat on the shins. Inflammation of fat is called panniculitis. It is caused by a hypersensitivity reaction. In around half of patients there is no identifiable cause. It is associated with a number of triggers and underlying conditions.
Associations
Erythema nodosum is caused by a hypersensitivity reaction, and there is often an identifiable cause:
- Streptococcal throat infections
- Gastroenteritis
- Mycoplasma pneumoniae
- Tuberculosis
- Pregnancy
- Medications, such as the oral contraceptive pill and NSAIDs
It is also associated with chronic diseases:
- Inflammatory bowel disease
- Sarcoidosis
- Lymphoma
- Leukaemia
TOM TIP: Erythema nodosum often indicates inflammatory bowel disease or sarcoidosis in exams.
Presentation
Erythema nodosum presents with red, inflamed, subcutaneous nodules across both shins. The nodules are raised and can be painful and tender. Over time the nodules settle and appears as bruises.
When you suspect someone has erythema nodosum it is important to look for signs and symptoms of potential triggers and underlying medical conditions.
Investigations
The diagnosis of erythema nodosum is based on the clinical presentation. Investigations can be helpful in assessing the underlying cause:
- Inflammatory markers (CRP and ESR)
- Throat swab for streptococcal infection
- Chest xray can help identify mycoplasma, tuberculosis, sarcoidosis and lymphoma
- Stool microscopy and culture for campylobacter and salmonella
- Faecal calprotectin for inflammatory bowel disease
Further imaging and endoscopy may be required under specialist guidance.
Management
Management mainly involves investigating for an underlying condition and treating the underlying cause.
Erythema nodosum is managed conservatively with rest and analgesia. Steroids may be used to help settle the inflammation.
Most cases will fully resolve within 6 weeks, however it can last longer.
Last updated January 2020