(BMJ)—A woman in her 70s presented with a 3-month hx of an itchy, burning rash that began on her arms and then spread to her trunk and legs. Review of sx: heartburn, weight loss, anorexia. Exam: diffuse papular, excoriated, lichenified gray-brown rash with hint of purple. Labs: marginally raised alk phos; hep C (+). What’s the dx?
Pityriasis rosea
Secondary syphilis
Guttate psoriasis
Lichen planus
Lichen simplex chronicus
You are correct. The rash was consistent with cutaneous lichen planus associated with active hep C infection. Lichen planus is an inflammatory skin disease often characterized by violaceous (purple) pruritic papules and plaques. The risk of being positive for antibodies to hep C is much higher in patients with lichen planus vs. controls (odds ratio, 4.85; absolute risk, 14.6% in patients with lichen planus). Also, the likelihood of concurrent hep C infection is 6x higher in people with oral lichen planus.

Consider screening for hep C in patients with newly diagnosed lichen planus if they have GI or systemic sx or risk factors for HCV. Also consider lichen planus in people with a widespread, itchy rash and hx of hep C.

The patient was started on antiviral tx for hep C, and within a few weeks, she reported an improvement in her rash.

BMJ 2021;372:m4976