Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 23-year-old woman is evaluated for 2 weeks of painful lumps on her legs. The lumps persist for several days and make it difficult for her to go to work as a waitress. She is a college student in Ohio where she has lived her whole life. She has not traveled outside of the state for the last 2 years. She has no swollen or painful joints. She denies abdominal pain, diarrhea, weight loss, night sweats, and fever. She is sexually active with one partner for the past 2 years. She is taking oral contraceptive pills.

On physical examination, vital signs are normal. There are tender faint pink-brown nodules on the shins bilaterally. The throat and tonsils appear normal. There is no joint swelling.

Pregnancy test is negative. Complete blood count, erythrocyte sedimentation rate, and antistreptolysin O titers are pending.

Barrier contraceptive methods are recommended in lieu of oral contraceptives.

Which of the following tests should be done next?

A. Biopsy of a nodule
B. Chest radiography
C. Colonoscopy
D. Nucleic acid amplification testing for gonorrhea

MKSAP Answer and Critique

The correct answer is B. Chest radiography.

This patient needs a chest radiograph to complete the evaluation of her erythema nodosum (EN). EN is the most common form of panniculitis, or inflammation of the fat, with most inflammation concentrated on the intralobular septae. Because the inflammation is deep under the skin, the clinical manifestation seen on the surface is often tender, ill-defined erythema with some substance on palpation, which may fade from an active inflammatory red-pink to dull brown. Most commonly, EN occurs bilaterally and symmetrically on the anterior shins; however, it may also appear in any fatty area. Although lesions will often come and go, most resolve over 4 to 6 weeks. EN is a nonspecific reaction pattern occurring in response to some systemic process. EN can be idiopathic, but the most common associations are streptococcal infection, hormones (including oral contraceptives, hormone replacement therapy, or pregnancy), inflammatory bowel disease, sarcoidosis, lymphoma, and medication reactions. The diagnosis of EN can be clinically based on the acute onset of tender nodules on the bilateral shins typically in a young woman. Biopsy is not necessary in typical lesions.

Most authorities recommend a chest radiograph in the evaluation of EN to assess for the presence of lymphoma, sarcoidosis, tuberculosis, and fungal infection such as coccidioidomycosis.

In the absence of gastrointestinal symptoms, a colonoscopy for inflammatory bowel disease is unlikely to reveal a causative diagnosis. Patients with disseminated gonococcal infection and bacteremia manifest vesiculopustular or hemorrhagic macular skin lesions, not tender subcutaneous nodules as seen in this patient.

Patients with disseminated gonococcal infection present with dusky pustules or purpura, fever, chills, and polyarthralgia. Knees, elbows, and distal joints are typical sites of involvement. Subcutaneous nodules are not features of this infection

A chest radiograph is recommended in the evaluation of erythema nodosum to assess for the presence of lymphoma, sarcoidosis, tuberculosis, and fungal infection such as coccidioidomycosis.

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