Musculoskeletal events such as arthralgia and myalgia may be partly explained by immune activation and cytokine release induced by HER2-targeted therapies [55], whereas dermatological symptoms like erythema and pruritus could be related to EGFR/HER family cross-inhibition [56], a mechanism known to underlie skin toxicity in targeted therapies. This evidence concerns the gene ERBB2 and Erythema.