We all know that I am not a “fan” of rashes and this is why I have a general “approach to pediatric rashes.” Part of this approach is perception of “sick vs not sick” and an assessment of the mucous membranes as we are looking for signs of significant systemic illness. With a child who appears ill and has mucous membrane involvement, our Ddx quickly populations with conditions like Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN); however, there is another entity that may be the etiology and can require alteration in our management plan. Let us take a moment to consider Mycoplasma pneumoniae Induced Rash and Mucositis:

Mycoplasma pneumoniae Induced Rash and Mucositis: Basics

Mycoplasma pneumoniae causes more than community acquired pneumonia.

Mycoplasma pneumoniae is a common cause of upper and lower respiratory tract infections in both children and adults.

It also, however, leads to extrapulmonary complications: [PMID 33094121: Gandelman, 2020; PMID 31517420: Chowdhury, 2019]
- Pericarditis
- Myocarditis
- Hepatitis
- Thrombocytopenic Purpura
- Autoimmune Hemolytic Anemia
- Acute Cerebellar Ataxia
- Dermatologic Eruptions occur in >20% of patients with it: [PMID 31851288: Sauteur, 2020]
  - Urticaria
  - Erythema Nodosum
  - Cutaneous Leukocytoclastic Vasculitis
  - Maculpapular Eruptions
  - Erythema Multiforme -> SJS -> TEN spectrum

While it may cause Stevens Johnsons spectrum of illness, it can also lead to a distinct entity known has Mycoplasma pneumoniae Induced Rash and Mucositis (MIRM).
- MIRM was first classified in 2015. [PMID 25592340l: Canavan, 2015]
- MIRM has a better predicted clinical course. [PMID 33094121: Gandelman, 2020; PMID 25592340l: Canavan, 2015]
- MIRM is often misdiagnosed as EM / SJS / TEN. [PMID 31517420: Chowdhury, 2019]

MIRM is different than EM / SJS / TEN

Compared to EM/SJS/TEN, MIRM will present with: [PMID 33094121: Gandelman, 2020; PMID 25592340l: Canavan, 2015]
- Limited or even No skin involvement
  - If present, it often is limited to extremities.
  - May be vesiculobullous.
  - Can be atypical targetoid (3 zones of different colors are seen with erythema multiforme).
  - Skin detachment, if present, is < 10% of body surface area.
- Prominent mucositis (at least two regions)
  - Oral surfaces
  - Ocular surfaces (ex, conjunctival injection, pseudomembrane formation, ulceration)
  - Genital surfaces (ex, urethral meatus)
  - Nares surface
  - Anal surfaces (essentially, mouth to anus and may cause GI irritation … look for occult blood in stool!) [PMID 26184002: Norton, 2015]
- Evidence of atypical pneumonia.
  - MIRM will often be preceded by a 1-week prodrome of cough, malaise, and fever.
  - Chest x-ray may show findings consistent with atypical pneumonia… but we know that that is not sensitive enough. [PMID 26184002: Norton, 2015]
  - Serologic testing, PCR testing, and/or Culture results may help define the diagnosis. [PMID 33094121: Gandelman, 2020]

Clinical findings of MIRM have also been associated with Chlamydia pneumoniae infection as well as viral infections. [PMID 28568680: Mayor-Ibarguren, 2017]
- Debate over how these fit together, but they also appear to be distinct from EM / SJS / TEN.
- Proposal to use term Reactive Infectious Mucocutaneous Eruption (RIME) instead of MIRM.

MIRM Management

Compared to EM / SJS / TEN, MIRM has an excellent prognosis.
- 81% of cases may a full recovery. [PMID 33094121: Gandelman, 2020]
- 3% morality rate. [PMID 33094121: Gandelman, 2020]

MIRM is most often seen in children who are ~12 years of age, although can occur in adults and younger children as well. [PMID 33094121: Gandelman, 2020; PMID 25592340l: Canavan, 2015]

Like EM / SJS / TEN, primary management is Supportive. [PMID 33094121: Gandelman, 2020; PMID 31517420: Chowdhury, 2019]
- No universally accepted guidelines.
- Reports of success with IVIG, steroids, and even cyclosporine.
- Good wound care is paramount.
- Ophthalmologists often are required for ocular care.

Unlike EM / SJS / TEN, antibiotics directed against atypical infections are useful. [PMID 33094121: Gandelman, 2020; PMID 31517420: Chowdhury, 2019]

Moral of the Morsel

All mucous membrane involvement does not equal SJS! The mucositis can be a very prominent feature of MIRM.
MIRM is not SJS, but may look the same initially. Ask more questions and look for evidence of recent or concurrent atypical pneumonia.
SJS = Stop the offending agent, while MIRM = Start the Macrolide. MIRM management should include antibiotics aimed at atypical infections!