Erythema multiforme - Oral Mucosal Lesion
In the past, the conditions EM, Stevens-Johnson syndrome (SJS), and toxic epidermal necrolysis (TEN) were considered a continuum, but it is now recognized that EM does not progress to TEN. Therefore, EM is now considered a distinct hypersensitivity eruption, which can be distinguished from SJS/TEN based on the presence of target lesions, papular (rather than macular) atypical target lesions, and an acral distribution.
In adults, the primary trigger for EM is herpes simplex virus (HSV), which is estimated to incite about 90% of cases. In children, important additional triggers to consider include drugs (particularly penicillin), mycoplasma pneumonia, group A Streptococcus, and Epstein-Barr virus. Importantly, mycoplasma pneumonia-induced EM is associated with prominent mucositis and absent or sparse cutaneous findings, which, if present, tend to have atypical morphology, including vesicles, bullae, targetoid lesions, and atypical targets / macules. The distinct cutaneous features seen in hypersensitivity eruptions due to mycoplasma pneumonia has led to the term "mycoplasma pneumonia-induced rash and mucositis" (MIRM), which some argue should be used to refer to any severe mucocutaneous eruption associated with mycoplasma pneumonia, abandoning the previous practice of classifying mycoplasma pneumonia-associated eruptions as EM, SJS, incomplete SJS, or mycoplasma pneumonia-associated mucositis. Many other infectious agents, both viruses and bacteria, have been associated with the development of EM.
Typically, all cutaneous lesions appear within 24-72 hours and persist for 2 weeks before fading. The eruption recurs on repeated exposure to the inciting agent. While HSV is the most common etiology associated with recurrent EM, several viruses have been associated as triggers, too.
EM demonstrates classical target lesions, raised atypical target lesions, or both concomitantly on the skin. In EM minor, little or no mucosal involvement is seen. In EM major, significant mucositis is seen. Painful intraoral and lip erosions eventuate from vesicles or bullae. Secondary crusting, including hemorrhagic crusting, then develops.
L51.9 – Erythema multiforme, unspecified
22972008 – Erythema multiforme, dermal type
- Stevens-Johnson syndrome (SJS) / toxic epidermal necrolysis (TEN) – Clinically, look for irregularly shaped, dusky red necrotic macules on the trunk, face, and palms / soles. A positive Nikolsky sign can be found. Oral involvement in SJS/TEN parallels that of EM; there is mucosal involvement, including the eyes, lips, mouth, and genitalia. Look for hemorrhagic crusts and intraoral erosions. Precipitating factors are usually medications.
- Mycoplasma pneumonia-induced rash and mucositis (MIRM) – Occurs secondary to mycoplasma infection as evidenced by clinical pneumonia, imaging studies, and/or mycoplasma serologies. There is pronounced oral and ocular mucositis with absent, spare, or mild cutaneous involvement. Hemorrhagic crusting is also seen. Cutaneous lesions are most often tense vesiculobullae. Target or targetoid lesions may be present. Nikolsky sign is negative. Acute and convalescent mycoplasma titers may be employed to help to establish this diagnosis in the correct clinical scenario.
- Fixed drug eruption – May involve the lips. Has a characteristic round shape.
- Herpes simplex virus
- Lichen planus – Whitish reticulated plaques may be seen on the lips and oral mucosa. Erosive intraoral forms are less frequently seen.
- Pemphigus vulgaris – Lips are usually spared.
- Mucous membrane pemphigoid – This condition mostly affects the mucosa and almost always the gingiva, although other sites may be involved.
- Bullous pemphigoid – Intraoral erosions may be seen.
- Epidermolysis bullosa acquisita – Intraoral vesicles or bullae and ulcers occur in a minority of patients.
- Aphthous stomatitis