Topical Imiquimod Induces Severe Weakness and Myalgias After Three Applications: A Case Report

Imiquimod can be used to treat superficial basal cell carcinoma, actinic keratosis, genital warts, and other skin conditions. The adverse events associated with this topical agent commonly include application site irritation, primarily erythema, as well as headache, myalgia, and fatigue. There are usually minimal systemic symptoms. We report the case of a patient who used topical imiquimod 5% cream on nine basal cell carcinoma lesions daily for three days and developed severe muscle weakness and the inability to walk. He fell twice, went to the emergency department, and was given 125mg injection of methylprednisolone. The imiquimod was then discontinued and he recovered almost back to baseline in 48 hours. We hypothesize the patient's reaction to the imiquimod was due to an immune etiology, potentially involving TLR7 and NF-κB as precipitators of this myopathy. Overall, this report demonstrates a potential severe and rapid adverse reaction to topical imiquimod administration not previously reported in the literature.