This study was done to investigate the phenotype and prognosis of RTD patients with late-onset MN.

The data for the analysis was obtained retrospectively collected clinical, biological and electrophysiological data from all French RTD 6 patients with MN onset after the age of 10 years and extracted data from 19 other similar RTD patients from the literature.

Adult RTD patients with MN had heterogeneous clinical presentations, potentially mimicking amyotrophic lateral sclerosis or distal hereditary motor neuropathy (56%), multineuritis with cranial nerve involvement (16%), Guillain-Barré syndrome 8%) and mixed motor and sensory neuronopathy syndromes (20%, only in SLC52A2 patients). Deafness was often diagnosed before MN (in 44%), but in some patients, onset began only with MN (16%). The pattern of weakness varied widely, and the classic pontobulbar palsy described in BVVL was not constant. Biochemical tests were often normal. The majority of patients improved under riboflavin supplementation (86%).

This study concluded that the late-onset RTD may mimic different acquired or genetic causes of motor neuropathies, it is a diagnosis not to be missed since high-dose riboflavin per oral supplementation is often highly efficient.