Combined study of 13 and complement genes in the diagnosis of thrombotic microangiopathies using next-generation sequencing

Abstract

The 2 main forms of thrombotic microangiopathy () are thrombotic thrombocytopenic purpura () and atypical hemolytic uremic syndrome (). Deficiency of 13 and dysregulation of the complement pathway result in and , respectively; however, overlap of their clinical characteristics makes differential diagnosis challenging. We aimed to develop a diagnosis workflow based on 13 activity and screening of ADAMTS13 and complement genes using a custom next-generation sequencing () gene panel. For this, from a cohort of 154 Portuguese patients with acute , the genotype-phenotype correlations were analyzed in 7 hereditary (13 activity <10%, no inhibitor), 36 acquired (13 activity <10%, presence of an inhibitor), and in 34 presumable . In total, 37 different rare variants, 8 of which novel (in ADAMTS13, , and CD46), were identified across 7 genes. Thirteen patients were homozygous (n=6), compound heterozygous (n=2), and heterozygous (n=5) for 11 ADAMTS13 variants (6 pathogenic mutations). Among the 34 patients, 17 were heterozygous for 23 variants in the different complement genes with distinct consequences, ranging from single pathogenic mutations associated with complete disease penetrance to benign variants that cause only when combined with other variants and/or and CD46 risk haplotypes or CFHR1-3 deletion. Our study provides evidence of the usefulness of the panel as an excellent technology that enables more rapid diagnosis of , and is a valuable asset in clinical practice to discriminate between and