Three patients (Patients E1, E6 and E7) were part of a cohort of 63 unrelated individuals with cranial neuropathies and sensorimotor neuropathy ± respiratory insufficiency that were Sanger sequenced for mutations in SLC52A1, SLC52A2 and SLC52A3. Seven patients (Patients A3–A7, U1 and U2; three probands and four affected siblings) had SLC52A2 mutations found through exome sequencing. Here, SLC52A2 is linked to Respiratory insufficiency.