CSS is usually sporadic, was refractory to conventional linkage but now know to be due to mostly de novo AD variants in several genes, including CSS1 caused by variants in ARID1B (OMIM#135900), CSS2 (ARID1A, OMIM#614607), CSS3 (SMARCB1, OMIM#614608), CSS4 (SMARCA4, OMIM#614609), CSS5 (SMARCE1, OMIM#616938), CSS6 (ARID2, OMIM#617808), CSS7 (DPF2, OMIM#601671), CSS8 (SMARCC2, OMIM#601734), CSS11 (SMARCD1, OMIM#618779). The gene discussed is SMARCD1; the disease is Alzheimer disease.