A Case of Mycoplasma pneumoniae-Induced Rash and Mucositis: A Histologic and Clinical Mimic of Erythema Multiforme and Stevens-Johnson Syndrome

Summary: Mycoplasma pneumoniae-induced rash and mucositis (MIRM) is challenging to distinguish as it is a clinical and histologic mimic of erythema multiforme (EM), Stevens-Johnson syndrome (SJS), and toxic epidermal necrolysis (TEN). Early identification and distinction from EM/SJS/TEN is paramount for prompt and appropriate care. Herein, we present a case study and literature review of M. pneumoniae induced rash and mucositis. A 17-year-old girl presented with a 3-day history of lip edema, bronchospasm, and few tender oral ulcers with a reported history of self-resolving oral ulcers. A course of oral steroids and steroid mouthwash were prescribed to treat the suspected allergic reaction and aphthous ulcers. The patient returned with symptom exacerbation including additional oral ulcers, pharyngeal exudate, severe inflammatory conjunctivitis, targetoid vesicles on the hands, vulvar ulcers, and hematuria. The patient was admitted to the hospital and IV acyclovir initiated, suspecting EM. A punch biopsy was performed from the thumb, revealing interface dermatitis pattern with numerous dyskeratotic keratinocytes. Corresponding DIF was negative. The patient did not respond to antiviral treatment with continued disease progression. Re-review of patient history revealed a recent mild respiratory illness and M. pneumoniae IgM was positive while HSV I/II was negative; ultimately confirming the diagnosis of MIRM.