Rapid Clinical Updates: Gell and Coombs for the Hospitalist-Handout

Handout

Pdf Summary

This document reviews the Gell and Coombs hypersensitivity framework for hospitalized patients and highlights two important skin conditions that can be confused with infection.<br /><br />It explains that hypersensitivity reactions are common in the hospital, often triggered by medications or infections, and that correct classification can prevent unnecessary antibiotic changes, ICU transfers, and incorrect lifelong drug allergy labels. The Gell and Coombs system divides reactions into four types based on immune mechanism and timing. Type III hypersensitivity, or immune complex–mediated disease, typically appears hours to days after exposure and can present as leukocytoclastic vasculitis with palpable purpura, often on the lower extremities. In hospitalized patients, infection-related antigens are increasingly recognized as triggers, not just newly started antibiotics.<br /><br />The document also describes pyoderma gangrenosum, a neutrophilic dermatosis that can mimic severe skin infection. It causes rapidly progressive, painful ulcers with violaceous, undermined borders and heavy drainage. Pathergy is common, meaning lesions worsen after trauma or debridement. It is associated with inflammatory bowel disease, rheumatologic disorders, and hematologic malignancy. Because surgical debridement can worsen the condition, treatment should focus on immunosuppression and early dermatology consultation.<br /><br />Finally, it reviews necrotizing fasciitis, a life-threatening deep soft tissue infection. Key features include pain out of proportion to exam, rapidly spreading erythema or bruising, hemorrhagic bullae, and sepsis, though skin findings may be subtle early. It is a surgical emergency, and broad-spectrum antibiotics or imaging should not delay operative exploration when suspicion is high.

Keywords

Gell and Coombs

hypersensitivity

type III hypersensitivity

leukocytoclastic vasculitis

pyoderma gangrenosum

necrotizing fasciitis

immune complex disease

palpable purpura

pathergy

hospitalized patients