Exome and whole-genome sequencing studies have found several candidate variants possibly responsible for ET in a small number of families, in split genes such as FUS (designated as ETM4), HTRA2, TENM4 (designated as ETM5), SORT1, SCN11A, NOTCH2NLC (designated as ETM6), NOS3, KCNS2, HAPLN4, USP46, CACNA1G, SLIT3, CCDC183, MMP10, and GPR151. However, replication studies on FUS, HTRA2, TENM4, and NOTCH2NLC genes have found that these mutations are infrequent in other families and populations, while results on mutations of other genes remain to be replicated. The gene discussed is HTRA2; the disease is essential thrombocythemia.