Only mutations (not haploinsufficiency due to 15q11.2 BP1-BP2 microdeletions including the NIPA1 gene) have thus far been associated with autosomal dominant spastic paraplegia 6 / SPG6- linked hereditary spastic paraplegia: HSP (https://www.genecards.org/cgi-bin/carddisp.pl?gene=NIPA1&keywords=NIPA1). The gene discussed is IGFBP2; the disease is autosomal dominant complex spastic paraplegia.