SLIT3 and essential thrombocythemia: The non-synonymous variant identified in SLIT3 (c.3505G>C, p.(Val1169Leu); rs144799628) is highly conserved evolutionarily, is predicted to be deleterious or damaging by several in silico tools and has an allele frequency in the ExAC database of 0.0006407 (72/112370+2 homozygotes), which is below the estimates of the disease prevalence of ET at 2–4%.