The examples chosen for discussion here can be classified into two categories: (a) the hereditary spastic paraplegia (HSP) together with the hypomyelinating leukodystrophy (HLD) associated with mutations in the gene encoding the chaperonin of Group I, Hsp60, namely SPG13 and MitCHAP-60 (or hypomyelinating leukodystrophy 4 (HLD4) (OMIM #612233)) disease [4]; and (b) the distal sensory neuropathy associated with a mutation in the gene encoding one of the eight subunits of the Chaperonin of Group II, CCT [5,6]. This evidence concerns the gene HSPD1 and hypomyelinating leukodystrophy 4.