Contrast media and cutaneous reactions. Part 2: Delayed hypersensitivity reactions to iodinated contrast media.

Contrast media (CM) are an indispensable part of modern medical imaging. Adverse reactions to CM are uncommon, but frequently involve cutaneous symptoms. This two-part article reviews adverse events secondary to CM that are relevant to the practising dermatologist. Part 1 covers the classification of CM, immediate hypersensitivity reactions to CM and the newly described condition, gadolinium deposition disease. Given that there has only been two case reports to our knowledge of a delayed adverse reaction to gadolinium-based CM, this second part will focus on cutaneous delayed reactions caused by iodinated CM (ICM). Delayed hypersensitivity reactions to ICM commonly present as maculopapular exanthems, but more rarely, they can manifest as fixed drug eruptions, acute generalized exanthematous pustulosis, drug-related eosinophilia and systemic symptoms, Stevens-Johnson syndrome/toxic epidermal necrolysis, symmetrical drug-related intertriginous and flexural exanthema, graft-versus-host disease, vasculitis and iododerma. Delayed reactions to ICM may be underdiagnosed, as cutaneous symptoms may be attributed to oral medications, particularly if patients are on multiple drugs.