SLC52A2 and hereditary optic atrophy: We also found a subclinical visual impairment, probably an optic atrophy which is also described in RTD but more often with SLC52A2 variants than SLC52A3. Our report demonstrates that subclinical abnormal evoked potentials can be interesting diagnostic markers of RTD, especially in adults where other markers, biochemical but also genetic, can lack diagnostic sensitivity.