Mycoplasma pneumoniae infection commonly manifests as an upper or lower respiratory tract infection with associated fever, dyspnea, cough, and coryza. However, patients can present with extrapulmonary complications with dermatologic findings including mucocutaneous eruptions. M. pneumoniae–associated mucocutaneous disease has prominent mucositis and typically sparse cutaneous involvement. The mucositis usually involves the lips and oral mucosa, eye conjunctivae, and nasal mucosa and can involve urogenital lesions. It predominantly is observed in children and adolescents. This condition is essentially a subtype of Stevens-Johnson syndrome, with a specific infection-associated etiology, and has been called “Mycoplasma pneumoniae–induced rash and mucositis,” shortened to “MIRM.”
Severe reactive mucocutaneous eruptions include erythema multiforme (EM), Stevens-Johnson syndrome (SJS), and toxic epidermal necrolysis (TEN). While there has been semantic confusion over the years, there are some distinctive characteristics.
EM is characterized by typical three-ringed target papules that are predominantly acral in location and often without mucosal involvement. The lesions are “multiforme” in that they can appear polymorphous and evolve during an episode, with erythematous macules progressing to edematous papules, sometimes with a halo of pallor and concentric “target-like” appearance. Lesions of EM are fixed, meaning individual lesions last 7-10 days, unlike urticarial lesions that last hours. EM classically is associated with herpes simplex virus infections which usually precede its development.
SJS and TEN display atypical macules and papules which develop into erythematous vesicles, bullae, and potentially extensive desquamation, usually presenting with fever and systemic symptoms, with multiple mucosal sites involved. SJS usually is defined by having bullae restricted to less than 10% of body surface area (BSA), TEN as greater than 30% BSA, and “overlap SJS-TEN” as 20%-30% skin detachment.1 SJS and TEN commonly are induced by medications and on a spectrum of drug hypersensitivity–induced epidermal necrolysis.
MIRM has been highlighted as a distinct, common condition, usually mucous-membrane predominant with involvement of two or more mucosal sites, less than 10% total BSA, the presence of few vesiculobullous lesions or scattered atypical targets with or without targetoid lesions (without rash is called MIRM sine rash), and clinical and laboratory evidence of atypical pneumonia.2 Other infections can cause similar eruptions (for example, Chlamydia pneumoniae), and a recent proposal by the Pediatric Dermatology Research Alliance has suggested the term “Reactive Infectious Mucocutaneous Eruption” (RIME) to include MIRM and other infection-induced reactions.
Laboratory diagnosis of M. pneumoniae is via serology or polymerase chain reaction. Antibody titers begin to rise approximately 7-9 days after infection and peak at 3-4 weeks. Enzyme immunoassay is more sensitive in detecting acute infection than culture and has sensitivity comparable to the polymerase chain reaction if there has been sufficient time to develop an antibody response.
The differential diagnosis between RIME/MIRM, SJS, and TEN may be difficult to distinguish in the first few days of presentation, and consideration of infections and possible medication causes is important. DRESS syndrome (drug reaction with eosinophilia and systemic symptoms) also is in the differential diagnosis. DRESS usually has a long latency (2-8 weeks) between drug exposure and disease onset.
Treatment of RIME/MIRM is supportive care and treatment of any underlying infection. Steroids and intravenous immune globulin (IVIG) have been used to treat reactive mucositis, as well as cyclosporine and biologic agents (such as etanercept), in an attempt to minimize the extent and duration of mucous membrane vesiculation and denudation. While these drugs may help shorten the duration of the disease course, controlled trials are lacking and there is little comparative literature on efficacy or safety of these agents.
Dr. Eichenfield is chief of pediatric and adolescent dermatology at Rady Children’s Hospital–San Diego. He is vice chair of the department of dermatology and professor of dermatology and pediatrics at the University of California, San Diego. Dr. Bhatti is a research fellow in pediatric dermatology at Rady Children’s Hospital and the University of California, San Diego. They said they have no financial disclosures. Email Dr. Eichenfield and Dr. Bhatti at email@example.com.