TBCE and proximal spinal muscular atrophy: The motoneuron disease of non-5q-SMA patients is caused by a spontaneous point mutation (c.1682T>G) in the tubulin-specific chaperone E (TBCE) gene on chromosome 13 (4), where tryptophan is exchanged to glycine (W524G) at the C-terminal of the protein (5, 6).