APOH and Down syndrome: ANA, antinuclear antibody; anti-β2GP1 IgG, anti-beta-2 glycoprotein 1 IgG antibodies; anti-β2GP1 IgM, anti-beta-2 glycoprotein 1 IgM antibodies; anti-dsDNA, anti-double-stranded deoxyribonucleic acid antibodies; anti-La/SSB, anti-La/anti-Sjögren’s-syndrome-related antigen B antibodies; anti-Ro/SSA, anti-Ro/anti-Sjögren’s-syndrome-related antigen A antibodies; anti-Sm, anti-Smith antibodies; GP1 IgG units, glycoprotein 1 IgG units; GP1 IgM units, glycoprotein 1 IgM units; UPCR, urine protein-to-creatinine ratio