SLC1A4 and quadriplegia: Two of these genes have been linked with human disease previously, biallelic germline pathogenic variants in SLC1A4 were reported to cause an autosomal recessively inherited disorder characterised by spastic tetraplegia, thin corpus callosum and progressive microcephaly (MIM 616657) [28–30] and compound heterozygous or homozygous mutations in FOCAD were associated with severe congenital liver disease (MIM 619991) [31].