Mycoplasma pneumoniae-induced rash and mucositis in Adult
The pathophysiology underlying MIRM remains poorly defined. Direct cytotoxic injury, autoimmune-mediated injury, and immune complex-mediated vascular injury have all been proposed as potential etiological mechanisms. It is speculated that a genetic predisposition is also important. More recent work has postulated that autoantibodies produced as a result of molecular mimicry between M pneumoniae and endogenous proteins cross-react with specific self-antigens that are most abundant in mucous membranes. This theory helps explain why mucositis is such a salient feature. Chlamydia pneumoniae infection has also been suggested as a potential causative agent (C pneumoniae-induced rash and mucositis, or CIRM), sometimes without rash.
Prodromal symptoms of cough, fever, and malaise precede mucocutaneous manifestations by approximately a week. Mucositis is a prominent feature and is usually associated with a sparse, polymorphic eruption.
Complications may include hematemesis, epiglottitis, subcorneal pustulosis, pneumomediastinum, pericardial effusion, and hepatitis.
Ocular sequelae include conjunctival shrinkage, corneal ulceration, blindness, synechiae, dry eyes, and loss of eyelashes. Oral or urogenital adhesions are less common. Pulmonary complications such as restrictive lung disease and chronic obliterative bronchitis have also been observed in MIRM patients.
MIRM is very rarely fatal and has a reported mortality rate of 3%, occurring in cases with significant respiratory disease. Most patients make a full recovery, and both long-term complications and recurrences are infrequent.
B96.0 – Mycoplasma pneumoniae [M. pneumoniae] as the cause of diseases classified elsewhere
406595002 – Infection caused by Mycoplasma pneumoniae
- The cutaneous involvement of MIRM tends to be much less extensive than in SJS and TEN (<10% of body surface area is usually affected).
- The cutaneous lesions of MIRM are usually distributed in acral regions compared to SJS and TEN, which exhibit a more central distribution of lesions.
- The desquamation associated with SJS and TEN is absent in MIRM (Nikolsky sign is negative).
- MIRM has a much milder course than SJS and TEN, eg, ICU admission is less commonly required.
- Absence of exposure to a culprit drug favors MIRM, as most cases of SJS and TEN are drug-related.
- Evidence of atypical pneumonia, including respiratory symptoms, lung auscultation findings, M pneumoniae serology, polymerase chain reaction (PCR), and chest x-ray results, may help support MIRM diagnosis.
- The classic target lesions occurring in an acral distribution that are typical of EM are less common in MIRM.
- Unlike EM, cutaneous lesions may be absent in MIRM.
- Evidence of atypical pneumonia, including respiratory symptoms, lung auscultation findings, M pneumoniae serology, PCR, and chest x-ray results, may help support MIRM diagnosis.
- Typical round morphology is diagnostic.
- MIRM lacks a temporal relationship to drug exposure.