[Immunopathology of cutaneous drug eruptions]

Adverse drug reactions (ADR) are common and may present clinically and histologically in a very heterogeneous manner. The pathophysiological understanding about causal immunological and non-immunological events has developed significantly over the past years. Skin and mucosa are commonly affected and are prone for histopathological examination. Certain groups of drugs such as immune checkpoint inhibitors may cause specific adverse reactions.

To provide a comprehensive overview of the complex immunological events and the most common dermatohistopathological findings of cutaneous adverse drug reactions.

Review of the literature (PubMed), own study data and pictures obtained via routine diagnostics at the University of Bonn.

Drugs may induce a wide range of skin reactions displaying a diversity of cutaneous inflammatory patterns. Histopathological clues for drug eruptions may be: eosinophils, lichenoid infiltrate and isolated keratinocytic apoptosis; a thorough medical history and correlation of clinical findings and dermatohistopathology are most important. Knowledge of typical adverse reactions to checkpoint inhibitors and their management is of great clinical interest as their use is rising steadily.