Arl6IP1 and protrudin are also known as SPG (spastic paraplegias) 61 and SPG33, respectively, because hereditary spastic paraplegias, a group of inherited neurological disorders whose pathology is characterized by axonal degeneration of corticospinal motor neurons, is caused by pathogenic mutations in Arl6IP1 and Protrudin genes (35, 36, 37, 38). This evidence concerns the gene ZFYVE27 and hereditary spastic paraplegia.