A genetic mutation was detected by our clinic in two sisters in a family with low iron levels and mild symptoms. We identified this missense mutation in the FTL gene (c.473T > C; p.Pro158Leu, rs374486686) of the sisters who had weakness symptom and low serum ferritin level. This mutation causes the codon CCG changing into CTG, thus composing an amino acid substitution in which proline 158 is replaced by leucine. The patients with this mutation had unmeasurable serum ferritin levels while other iron parameters' levels are normal. As a result of this mutation, we demonstrated that ferritin connects iron however it can not store iron.