SDCBP and systemic lupus erythematosus: Extrapolating from dogs, a hypothetical human patient with UNC93B1-related SLE would, therefore, be required to carry either bi-allelic UNC93B1 variants abrogating SDCBP binding or a combination of one mutant allele encoding a UNC93B1 protein with impaired SDCBP binding together with a complete loss-of-function allele on the second chromosome.