An 18‐year‐old female with a history of panniculitis presented with a painful rash. Two years prior to presentation, the rash initially appeared as painful, raised, dark red/purple “bruises” over her shins, thighs and abdomen; it was associated with weight loss, fever, malaise, anemia and alopecia. A clinical diagnosis of panniculitis with erythema nodosum (EN) was made. She travelled to Mexico where she received IV corticosteroids and subsequently improved. During the year before presentation, she had recurrent episodes requiring repeated courses of oral prednisone for relief; her tuberculin skin test was positive with induration to 9 mm, ESR and CRP were elevated, her ANA was negative, and she did not receive treatment for mycobacterial infection. At the current presentation, she complained of only the rash and denied any symptoms or signs of pulmonary tuberculosis (TB). Physical examination revealed multiple 3 cm, painful, erythematous subcutaneous nodules on her bilateral upper thighs. Although her PPD was negative, a QuantiFERON Gold test was positive. A punch biopsy of the lesion showed septal panniculitis with minimal lobular involvement. She was diagnosed with EN and was treated with isoniazid (INH) for latent TB. She was later switched to INH, rifampin, pyrazinamide and ethambutol (four‐drug RIPE therapy) after developing recurrent EN while on INH monotherapy. Her EN clinically improved and did not recur with RIPE therapy.
Erythema nodosum is a delayed hypersensitivity reaction to antigens occurring secondary to streptococcal infection, autoimmune disease or fungal infections, depending on the country of the patient’s origin. Screening labs, including a complete blood count, comprehensive metabolic panel, chest roentogram, anti‐streptolysin O (ASO) titers, and TB skin testing, are recommended to elucidate etiology; a biopsy is required only in atypical cases. If a biopsy is necessary, deep excisional biopsy is preferred and typically shows panniculitis with septal inflammation in the subcutaneous fat tissue, usually without associated vasculitis. Polymerase chain reaction (PCR) detection of TB in the tissue has high sensitivity and specificity, and it should have been performed in the above case. One Chinese study demonstrated that almost all patients with primary TB presented with EN, and 20% of those with EN had tuberculosis. Females have an increased risk of developing EN from TB compared to males, but males tended to have active TB more frequently than females. A four‐drug regimen for TB is recommended for treatment; corticosteroids are discouraged for the treatment of TB‐associated EN.
Although TB is a common cause of erythema nodosum, it remains a diagnostic challenge because TB is typically only found in the biopsy specimens of those with active disease. There are very few studies regarding the treatment of EN in the context of TB, and most experts use a four‐drug TB regimen for treatment of TB‐associated EN.
To cite this abstract:Bhadriraju S, Bates J. Latent Tuberculosis Infection Causing Erythema Nodosum. Abstract published at Hospital Medicine 2014, March 24-27, Las Vegas, Nev. Abstract 347. Journal of Hospital Medicine. 2014; 9 (suppl 2). https://www.shmabstracts.com/abstract/latent-tuberculosis-infection-causing-erythema-nodosum/. Accessed April 1, 2020.