SLC52A2 and neuropathy: RF transporter deficiency (RTD; also known as Brown-Vialetto-Van Laere syndrome) is a progressive inherited neuropathy with childhood onset, caused by mutations in SLC52A2 (RTD2) or SLC52A3 (RTD3), which encode the human RF transporters 2 (RFVT2) and 3 (RFVT3), respectively [2,10,20,23].