"This sign is seen in hereditary spastic paraplegia with thin corpus callosum (HSP-TCC), the commonest form of which is spastic paraplegia 11 (SPG11), a form of hereditary spastic paraplegia associated with mutations of the identically-named spastic paraparesis gene 11 (SPG11) on chromosome 15 which codes for spatacsin 1,2."
"SPG15, another cause of "hereditary spastic paraplegia with thin corpus callosum", which is caused by a mutation in the zinc finger five domain-containing protein 26 (ZFYVE26) gene, encoding spastizin"