Page 58 - Haematologica May 2022

M. Guipponi et al.
keeps a religious faith different to the surrounding vil- lages in the area. While the surrounding villages have a 'Sunni' faith, the village where the patients live has an Alavian-Bektashi faith. Since there are no marriages between these two religious groups, all marriages are between individuals from the same village. Interestingly, the original founders migrated from the Iranian province of Mazandaran, formerly known as Taberistan, during the 9th and 10th centuries. Current inhabitants of Maznandar are also of Alavian-Bektashi faith.
Bleeding severity was assessed according to the score from the EN-RBD study.17 Patients were divided into clin- ical bleeding severity categories (asymptomatic and grade 1, 2, or 3 bleeding). Category 1 refers to provoked bleed- ing episodes, category 2 refers to spontaneous minor bleeding episodes (e.g., bruising), and category 3 refers to spontaneous major bleeding episodes (e.g., cerebral bleeds or hemarthrosis).17 Of the eight patients diagnosed with afibrinogenemia (Figure 1), four were available for genetic analysis. Fibrinogen measurements, both anti- genic and coagulable, were performed for 41 additional family members (Table I).
Three patients available for study were male (patient ID: 1283, 1316, and 1317), and one was female (patient ID: 1314). All patients with afibrinogenemia have a severe clinical phenotype (grade 3) while most heterozy- gous patients with hypofibrinogenemia have a grade 0 (mean, 0.5). No patient received fibrinogen on prophylax- is. Two male patients with afibrinogenemia (1283 and
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1317), for which no additional clinical information is available, have experienced a thrombotic event. This is not unusual; afibrinogenemia is associated with an increased thrombotic risk even in the absence of addition- al thrombotic risk factors, whether genetic or environ- mental. In a recent study of 204 afibrinogenemic patients, 37 (18 %) reported a thrombotic event.18
Identification of a duplication of the FGG exon 8- intron 8 junction
We aimed to identify the causative mutation by first screening three affected patients (1314, 1317 and 1283) and one heterozygous carrier (1288) by PCR amplification of all FGB, FGA and FGG coding regions and intron-exon junc- tions followed by Sanger sequencing as previously described.16 This approach was unsuccessful, no causative mutation was identified. We then performed array-CGH analysis and identified 23 variants not listed in the database of Genomic Variants (http://dgv.tcag.ca/dgv/app/home). However none of these variants was a candidate for the afibrinogenemia phenotype so this approach was also unsuccessful.
Finally, as part of our ongoing research project deter- mining the causative mutations and genetic modifiers of congenital fibrinogen disorders which uses WES followed by variant calling in a panel of selected genes including the fibrinogen genes, we included one heterozygous car- rier, 1292, the mother of affected patient 1283, in the study. A detailed analysis of the reads suggested the pres-
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Figure 1. Family tree of the large consanguineous family.
(A) Main family tree. (B) Other family members including rel- atives of individual 1305 (indicated with an asterisk).
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