Indeed, additional germline variants in KIT and in genes encoding for cytokines or their receptors (e.g., IL13, IL6, IL6R, IL31, IL4R), as well as increased copy numbers of the TPSAB1 gene encoding for α‐tryptase, have been increasingly recognized as associated with systemic mastocytosis in adults.153. Here, IL31 is linked to systemic mastocytosis.