SPG7 and cerebellar ataxia: In the homozygous context of our patients, the reduced levels of homo-oligomeric m-AAA proteases and the almost complete absence of hetero-oligomeric m-AAA isoenzymes explain the striking combination of clinical features of both SPG7 and SCA28, including spastic paraplegia, ptosis, and cerebellar ataxia [2], [4], [6], [22].