Erythema nodosum

Question 1

Define erythema nodosum. Which parts of the body does it affect?

Answer 1

Erythema nodosum (EN) is a common cutaneous hypersensitivity reaction consisting of erythematous, tender nodules most commonly located over the shins, but also reported over the thighs, upper extremities, calves, buttocks, and face. Fever and arthralgia may also be present.

Question 2

How common is erythema nodosum?

Answer 2

Peaks between 20-30yrs

More common in Europe than North America

Women affected 3-6 times more than men

Common in women of childbrearing age, pregnancy and lactation.

Question 3

What are the causes of/risk factors for erythema nodosum?

Answer 3

Usually idiopathic in 60%

• Bacterial
• Fungal
• Viral and chlamydial
• Drug-induced e.g. sulfonamides, COCP
• UC and GI disease e.g. IBD, Behcet’s
• Malignancy - lymphoma, leukaemia
• Miscellaenous e.g. sarcoid

Question 4

Which layer of skin is affected by erythema nodosum?

Answer 4

Subcutaneous fat

Question 5

Which common GI inflammatory disease manifests as erythema nodosum?

Answer 5

Erythema nodosum is the most common cutaneous manifestation of inflammatory bowel disease.

Can be soceondary to these ulcerative diseases of the gastrointestinal tract:

• Crohn’s disease
• Ulcerative colitis
• Behcet’s disease.

Question 6

What are the clinical features of erythema nodosum?

Answer 6

• Lesions are red, tender, non-ulcerated, immobile nodules
• Typically resolving in 8 weeks
• Nodules on shins or other areas
• Patients with brucellosis or histoplasmosis may have an enlarged spleen and abnormal retinal examination
• Joint pains - generalised and may suggest underlying rheumatological cause
• Fever
• Inflammation of the throat and tonsil may suggest streptococcal infection even in absence of ASO

Question 7

What investigations would you do for erythema nodosum?

Answer 7

Erythema nodosum is primarily a clinical diagnosis

Bloods: do on initial presentation and 2-4 weeks later

• FBC
• Anti-streptolysin-O (ASO)
• ESR - elevated
• Tuberculin
• Serology - If no TB but hilar enlargement. Coccidioidin or histoplasmin skin tests, serological testing for blastomycosis, and serological testing for brucellosis or psittacosis may be indicated.
• Stool cultures - Yersinia

Imaging:

• CXR - indicated in all patients. Bilateral hilar adenopathy in sarcoidosis and unilateral hilar node enlargement in tuberculosis, coccidioidomycosis, and brucellosis.

Invasive:

• Endoscopy - for IBD
• Skin biopsy - if lesions are atypical; ulceration/abnormal distribution/unresponsive. Need adequate sample of subcutaneous fat.

Question 8

What is the presentation of Lofgren’s syndrome?

Answer 8

Lofgren’s syndrome is the presentation of uveitis, arthralgias, and fever with EN nodules. Serum ACE is elevated in about 60% of sarcoidosis patients.

Question 9

How is erythema nodosum managed?

Answer 9

Treat underlying cause

1. Bed rest and leg elevation + analgesia- NSAIDs (aspirin or ibuprofen) preferred

2. Potassium iodine - 300mg TDS (6 drops) PO; for severe cases, if no response to initial therapy. The mechanism is unclear.

3. Intralesional corticosteroid injection - for painful persistent nodules.

Question 10

What are the complications of erythema nodosum?

Answer 10

Ulceration - very rare. Consider other diagnoses if this occurs.

Question 11

What is the prognosis with erythema nodosum?

Answer 11

Spontaneous recovery within 1-2 months

Usually no scarring

Older patients may have persistent swelling especially if they also have venous insufficiency