Erythema Induratum

Erythema Induratum – 3 Interesting Facts

1. Erythema Induratum is more common in clinical populations with a strong exposure to tuberculosis.
2. The treatment of choice is to identify any underlying cause (e.g., tuberculosis) and treat that disorder or withdraw any potentially offending drug.
3. Untreated lesions tend to persist for months or even years and when the lesions resolve, they may heal with atrophy and variable scarring.

Introduction

• The term erythema induratum (of Bazin) is often used interchangeably with the term nodular vasculitis, although some dermatologists reserve the former for cases that are tuberculosis-associated and the latter term for those that are not.

What causes Erythema Induratum?

• The pathogenesis is not entirely understood, although in cases associated with tuberculosis, polymerase chain reaction (PCR) studies have demonstrated Mycobacterium tuberculosis DNA in more than 75% of cases, suggesting that it is a hypersensitivity reaction.

What are the Risk Factors?

• Less common associations have included Crohn disease, other infections, and, very rarely, medications (e.g., propylthiouracil).

Workup

History

• Regarding the clinical presentation, be particularly suspicious in a patient with a known history of tuberculosis or exposure to individuals with active tuberculosis.
• It usually affects young and middle-aged women, although any age or gender can be affected.
• It is more common in clinical populations with a strong exposure to tuberculosis.

Physical Examination

• It is usually located on the calves and shins, although the trunk, upper extremities, and even the face can be affected.
• The primary lesion is comprised of one or more painful, erythematous, subcutaneous nodules.
• Ulceration is frequently present in one or more lesions, a finding that is not found in erythema nodosum.

Imaging Studies

• Chest x-rays are strongly recommended in all cases to exclude evidence of tuberculosis.

Diagnostic Procedures

• The diagnosis is typically established by a 5- to 8-mm punch biopsy or incisional biopsy. It is critical that the biopsy includes adequate subcutaneous fat. The histologic findings may be strongly suggestive or diagnostic. Cases associated with tuberculosis are culture negative and do not demonstrate organisms with special stains; they can only be demonstrated by PCR assay, which is not routinely available.
• A purified protein derivative (PPD) skin test is strongly recommended in all cases to exclude evidence of tuberculosis. If tuberculosis is strongly suspected, consider diluting the PPD to 1 : 10, because patients may demonstrate very exuberant reactions.

Differential Diagnosis

• Erythema nodosum
• Lupus panniculitis
• Polyarteritis nodosa
• Other rare forms of panniculitis

Treatment

Approach to Treatment

• The treatment of choice is to identify any underlying cause (e.g., tuberculosis) and treat that disorder or withdraw any potentially offending drug.

Drug Therapy

• Use oral prednisone, starting at a dose of 10 to 40 mg/day, that is tapered as quickly as possible as the patient responds to therapy. Prednisone is not recommended until active tuberculosis has been excluded.
• Oral potassium iodide (SSKI) is an alternate therapy, starting at two drops three times per day and increasing up to six drops three times per day.
• NSAIDs may be used to reduce pain and inflammation.

References

1.Gilchrist H, Patterson JW. Erythema nodosum and erythema induratum (nodular vasculitis): diagnosis and management. Dermatologic therapy. 2010;23(4):320-327.

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