A 33-year-old woman comes to the office due to skin lesions and pain in her ankles for a week. She has had no cough, sore throat, shortness of breath, abdominal pain, or bowel symptoms. She reports no recent travel or illness. The patient has no other significant medical history and takes no medications. She does not use tobacco, alcohol, or illicit drugs. She has no history of sexually transmitted diseases and has been married to a monogamous partner for the past 8 years. Her mother was diagnosed with ovarian cancer at age 65. Temperature is 37.2 C (98.9 F) and blood pressure is 126/76 mm Hg. On examination, the patient has multiple tender pink to reddish nodules below the knee, as shown in the exhibit. Which of the following is the most appropriate next step in management?
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This image depicts erythema nodosum (EN), which is characterized by painful, subcutaneous nodules that are most common on the anterior lower legs. Arthralgias and malaise can develop alongside the nodules. EN is thought to represent a delayed hypersensitivity reaction to antigens associated with various conditions and is often relatively benign with self-resolution in several weeks. However, EN can be an early sign of more serious disease, and identification of the cause may prevent morbidity. Diseases associated with EN include streptococcal infection, sarcoidosis, tuberculosis (TB), endemic fungal disease (eg, histoplasmosis), inflammatory bowel disease (IBD), and Behçet disease.
The initial workup includes basic laboratory tests (complete blood count, liver function, renal function), antistreptolysin-O antibodies, and TB skin testing. In addition, a chest x-ray should be obtained to assess for findings consistent with sarcoidosis (eg, bilateral hilar lymphadenopathy, reticular opacities) or with TB (unlikely in the absence of symptoms). The prevalence of sarcoidosis in patients with EN is as high as 28% in some populations. The absence of pulmonary symptoms (eg, dyspnea, cough) in this patient does not rule out sarcoidosis as up to 50% of cases are diagnosed by incidental chest x-ray findings prior to symptom development.
(Choice A) Antinuclear antibodies have high sensitivity for systemic lupus erythematosus (SLE) and can be useful in ruling it out. However, SLE is not a common cause of EN.
(Choice B) Skin biopsy is not indicated in diagnosing the etiology of EN except in cases with atypical appearance or in areas where TB is endemic. In addition, in patients with sarcoidoisis, biopsy of EN lesions typically shows nonspecific panniculitis rather than the classic noncaseating granulomas associated with the disease.
(Choices D and E) EN can occur due to inflammatory bowel disease (IBD) (more commonly Crohn disease than ulcerative colitis), typically during periods of active intestinal disease. This patient has no symptoms to suggest IBD (eg, abdominal pain, diarrhea, fever), and therefore colonoscopy is not indicated. CT scan of the abdomen is generally not helpful in diagnosing the etiology of EN.
(Choice F) An association between HIV and EN is not well established, and HIV testing is not part of the initial workup.
(Choice G) Neisseria gonorrhoeae has no known association with EN, and Chlamydia trachomatis has only a rare association with EN. Testing for these organisms is not indicated in the initial workup.
Educational objective:
Erythema nodosum (EN) is a condition of painful, red or violaceous, subcutaneous nodules. It can be a sign of a more serious disease process. Even in the absence of respiratory symptoms, chest x-ray should be performed in patients with EN to assess for findings consistent with sarcoidosis.