Another study involving 381 sporadic CH cases (232 trios) identified several new risk genes of CH including PIK3CA (phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha), PTEN (phosphatase and tensin homolog), mTOR (mechanistic target of rapamycin kinase), FMN2 (formin 2), and FXYD2 (FXYD domain-containing ion transport regulator 2) [19]. This evidence concerns the gene FXYD2 and cyclic hematopoiesis.