PGAP1 and hemochromatosis type 4: When applying the above mentioned filtering steps, we were by both affected children once again left with the variants in PGAP1 and SLC40A. Since mutations in SLC40A cause hemochromatosis of type 4 and have no effect on cognition (MIM 606069) [26], [27], we focused on the variant in PGAP1, NM_024989.3:c.589_591delCTT, NP_079265.2:p.Leu197del.