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Complement-mediated atypical hemolytic uremic syndrome (aHUS) is an ultra-rare renal disease primarily caused by genetic alterations in complement proteins. The genetic work-up required for confirmation of diagnosis is complicated and not always logistically accessible. The aim of the present study was to apply a diagnostic scheme compliant with the American College of Medical Genetics and Genomics guidelines to investigate the prevalence of complement-mediated aHUS among subjects formerly included in a retrospective cohort of clinically suspected aHUS. Clinical outcomes and genetic correlations to complement analyses were assessed. Subjects were investigated with medical record reviewing, inquiries, and laboratory analyses composed of whole genome sequencing; enzyme-linked immunosorbent assays for factor I, factor H, and factor H-specific antibodies; nephelometry for complement components three of four; flow cytometry for CD46 surface expression and immunoblotting for the presence of factor H-related protein 1. In total, 45% (n = 60/134) of the subjects were deceased at the time of study. Twenty of the eligible subjects consented to study participation. Based on genetic sequencing and clinical characteristics, six were categorized as definite/highly suspected complement-mediated aHUS, 10 as non-complement-mediated aHUS and four as having an HUS-like phenotype. In the complement-mediated aHUS group, two subjects had not received an aHUS diagnosis during the routine clinical management. Disease-contributing/likely disease-contributing genetic variants were identified in five subjects, including a novel missense variant in the complement factor H gene (c.3450A>G, p.I1150M). This study illustrates the risk for misdiagnosis in the management of patients with complement-mediated aHUS and the importance of a comprehensive assessment of both phenotype and genotype to reach a diagnosis., (© 2021 The Authors. Therapeutic Apheresis and Dialysis published by John Wiley & Sons Australia, Ltd on behalf of International Society for Apheresis, Japanese Society for Apheresis, and Japanese Society for Dialysis Therapy.)

: Fibrinogen is essential for normal hemostasis. Congenital fibrinogen disorders (afibrinogenemia, hypofibrinogenemia, dysfibrinogenemia and hypodysfibrinogenemia), caused by pathogenic variants in the genes FGA, FGB and FGG, have the potential of causing bleeding diathesis and/or thrombotic events of variable severity. We describe a case of familial hypofibrinogenemia in a Swedish family. The proband is a 27-year-old woman, with a history of significant bleeding diathesis. She was diagnosed with moderate hypofibrinogenemia (0.8 g/l), and genetic screening identified a rare heterozygous missense variant in FGB (c.854G>A, p.Arg285His) (Fibrinogen Merivale) previously described in a New Zealand European family with symptomatic hypofibrinogenemia. The father, sister and brother of the proband also harbored the FGB variant, segregating with hypofibrinogenemia (0.9-1.2 g/l). The proband showed a more severe bleeding phenotype compared with her other hypofibrinogenemic family members; this was attributed to a concomitant platelet dysfunction, also present in her normofibrinogenemic mother.