Morbilliform Eruptions: Differentiating Low-Risk Drug Eruptions, Severe Cutaneous Adverse Reactions, Viral Eruptions, and Acute Graft-Versus-Host Disease

Morbilliform eruptions, which are a clinical reaction pattern characterized by erythematous macules and papules coalescing into patches that cover most of the skin surface, are one of the most common cutaneous findings in the inpatient setting. In the hospital setting, most causes are benign and due to low-risk drug exanthems; however, morbilliform eruptions may also be a sign of high-risk diseases, including Stevens–Johnson syndrome/toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms/drug-induced hypersensitivity syndrome, acute generalized exanthematous pustulosis, and graft-versus-host disease. Proper identification of the etiology and risk stratification of a morbilliform eruption is critical to ensure proper management and optimize patient outcomes. In this review, we discuss the key features that differentiate high-risk from low-risk morbilliform eruptions, as well as specific characteristics that differentiate the different high-risk eruptions. Additionally, we offer a clinical algorithm that may be applied in the management of a patient who presents with a morbilliform rash.