What’s the Diagnosis? By Jake Barr, MS3

The patient is a 40-year-old male with no past medical history who presents with concerns of a rash on his hands. He states that the lesions appeared two days ago, but had a fever, muscle aches, and pruritis two days before that. He does not have a history of hives or contact dermatitis. He does not take any medications, but states he recently developed “cold sores.” His temperature is 100.6^oF, but his other vitals are within normal limits. The cutaneous rash is demonstrated below. When looking in his mouth, blistering lesions are also present. What the diagnosis and management?

Answer: Erythema Multiforme

• Erythema multiforme is the result of a T-cell mediated hypersensitivity reaction resulting in a characteristic pruritic, targetoid papules, with a hazy-center, and surrounding erythematous rings.
• 90% of cases are associated with infectious etiologies, with HSV-1 being most common in adults and Mycoplasma pneumonia in children.
  • Remaining 10% are due to drugs (NSAIDs, antiepileptics, antibiotics), malignancy, and autoimmune diseases. Their mechanism of rash formation is unknown.
• There are two specific subtypes:
  • Erythema multiforme minor: rash without mucosal involvement or constitutional symptoms
  • Erythema multiforme major: rash with mucous membrane involvement and constitutional symptoms (fever, malaise, myalgias etc.)
• Diagnosis is often clinical, but immunofluorescence can be helpful if uncertain.
  • PCR testing for both HSV and Mycoplasma pneumoniae should be done if suspected.
• Treatment is mostly symptomatic, and the rash is usually self-limited.
  • Antihistamines are useful for pruritis.
  • Systemic steroids maybe be used, but the impact on long-term outcomes and symptom duration is unclear.
  • Acyclovir may be used to prevent recurrent HSV infections.
  • Macrolides may be used in Mycoplasma pneumoniae is suspected.

References:

1. Baluzy Matthew, Karaze Tallib. Maculopapular Rashes. In: Mattu A and Swadron S, ed. CorePendium. Burbank, CA: CorePendium, LLC. https://www.emrap.org/corependium/chapter/recvFPlc0BmXxYuzp/Maculopapular-Rashes#h.til8vwjxmfh6. Updated June 21, 2023. Accessed January 24, 2024.
2. Sokumbi O, Wetter DA. Clinical features, diagnosis, and treatment of erythema multiforme: a review for the practicing dermatologist. Int J Dermatol. 2012;51(8):889-902. doi:10.1111/j.1365-4632.2011.05348.x
3. Trayes KP, Love G, Studdiford JS. Erythema Multiforme: Recognition and Management. Am Fam Physician. 2019;100(2):82-88.
4. J. Brady W, Pandit A, R. Sochor M. Generalized Skin Disorders. In: Tintinalli JE, Ma O, Yealy DM, Meckler GD, Stapczynski J, Cline DM, Thomas SH. eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 9e. McGraw-Hill Education; 2020. Accessed January 24, 2024. https://accessemergencymedicine.mhmedical.com/content.aspx?bookid=2353&sectionid=221180403
5. DermNet. https://dermnetnz.org/topics/erythema-multiforme-images