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. The gene discussed is IL13; the disease is systemic mastocytosis.