Another notable feature of the case described in this study is the presence of a thinning corpus callosum (TCC; Fig. 1A), which has been described as a subcategory of complex HSP, most commonly attributed to autosomal recessive mutations in SPG11 (spatacsin), with fewer cases caused by SPG21 (maspardin), SPG32, SPG15, and TUBB4A (13, 64). The gene discussed is SPG11; the disease is hereditary spastic paraplegia.