Sarah K. Westbury

Heritable platelet function disorders (HPFD) are a diverse group of bleeding disorders characterised by a primary qualitative defect in platelet function rather than platelet number. HPFD may be broadly categorised according to the severity of bleeding, with Glanzmann thrombasthenia and Bernard Soulier syndrome classically considered severe HPFD, with well‐described clinical and laboratory phenotypes. The remaining non‐severe HPFD are less completely characterised and provide additional challenges in diagnosis despite advances in standardising diagnostic approaches for HPFD. Distinguishing patients with non‐severe HPFD from patients who do not have a bleeding disorder may be aided by employing bleeding assessment tools early in patient assessment, although there may be limitations according to patient factors. Distinguishing patients with non‐severe HPFD from those with acquired platelet function disorders and from those with other heritable disorders of haemostasis (including bleeding disorder of unknown cause) requires more sophisticated clinical and laboratory tools, including platelet light transmission aggregometry, secretion and flow cytometry assays, which can categorise many HPFD to the level of the defective platelet pathway and some to the level of an individual protein. The increasing availability of high‐throughput genetic sequencing has made genetic diagnosis possible for some patients with non‐severe HPFD; however, this is limited by difficulties with standardisation of laboratory phenotyping and the challenges of distinguishing pathogenic from benign genetic variation. This review will focus on updates in diagnostic approaches for patients with non‐severe HPFD since the last IJLH education article on this topic in 2014.

Background: Venous thromboembolism (VTE) is a common complication of cancer. Complex interactions between tumour biology and the haemostatic system may contribute to development of cancer-associated VTE. Objectives: This study examined associations of somatic mutations with VTE in a large multi-cancer cohort. Methods: We analysed paired tumour and germline whole genome sequence data and electronic health records from 12,507 cancer patients recruited to the Genomics England National Genomic Research Library, to evaluate associations of somatic mutations across 608 genes, overall tumour mutational burden (TMB) and 25 single base substitution (SBS) mutational signatures with VTE. Interactions between somatic mutations and a germline polygenic risk score for VTE were also assessed. Results: In multivariable Cox regressions adjusted for age, sex and genetic ancestry, somatic mutations in four genes associated with higher rates of VTE at a false-discovery rate CDKN2A (Hazard ratio, HR=1.62 [95% confidence interval, 1.23-2.13]) , KRAS (HR=1.31 [1.12-1.53]), PCDH15 (HR=1.48 [1.24-1.76]) and TP53 (HR=1.55 [1.38-1.73] ). SBS8, a common mutation signature of unknown aetiology, was also associated with higher rates of VTE (HR=1.39 [1.16-1.66]). In contrast, TMB ≥20 mutations/Mb, two DNA mismatch repair signatures (SBS6 and SBS26) and one rare signature of unknown aetiology (SBS19) associated with lower rates of VTE. Evidence for these associations remained robust after additional adjustment for tumour type, stage, and systemic anti-cancer treatment. Conclusions: These findings support the hypothesis that tumour somatic mutations influence risk of VTE. This may provide insights into the pathophysiology of cancer-associated VTE and inform future efforts to improve clinical risk prediction.

Despite whole genome sequencing (WGS), why do many single gene disorder cases remain unsolved, impeding diagnosis and preventative care for people whose disease-causing variants escape detection? Early WGS data analytic steps prioritize protein-coding sequences. To simultaneously prioritise variants in non-coding regions rich in transcribed and critical regulatory sequences, we developed GROFFFY, an analytic tool which integrates coordinates for regions with experimental evidence of functionality. Applied to WGS data from solved and unsolved hereditary hemorrhagic telangiectasia (HHT) recruits to the 100,000 Genomes Project, GROFFFY-based filtration reduced the mean number of variants per DNA from 4,867,167 to 21,486, without deleting disease-causal variants. In three unsolved cases (two related), GROFFFY identified ultra-rare deletions within the 3’ untranslated region (UTR) of the proto-oncogene SMAD4 , where germline loss-of-function alleles cause combined HHT and colonic polyposis. Sited >5.4kb distal to coding DNA, the deletions did not modify or generate microRNA binding sites, but instead disrupted the sequence context of the final cleavage and polyadenylation site necessary for protein production: By iFoldRNA, an AAUAAA-adjacent 16 nucleotide deletion brought the cleavage site into inaccessible neighboring secondary structures, while a 4-nucleotide deletion unfolded the downstream RNA polymerase II roadblock. Monocyte SMAD4 RNA expression differed between patients and controls in resting and cycloheximide-stressed states. Patterns predicted the mutational site for an unrelated case, where a complex insertion was subsequently identified. In conclusion, a new type of functional rare variant is described, exposing novel regulatory systems based on polyadenylation. Extension of coding sequence-focused gene panels is required to capture these variants.

Postgraduate medical education faces ongoing disruption due to the COVID-19 pandemic, with specific challenges in providing training in laboratory medicine. We report an online approach that has enabled us to continue to deliver haematology morphology training in a teaching hospital setting. The method described is associated with high levels of participant satisfaction and could easily be adapted for use in other clinical pathology specialties.

FLNA is a 48-exon gene located at chromosome Xq28 that encodes the 280 kDa cytoskeletal protein filamin A (FLNa; UniProt P21333) [1,2]. The mature FLNa protein of 2646 amino acids comprises an amin...

Key Points: We report rare monoallelic variants of THPO that alter intracellular trafficking and diminish thrombopoietin secretion. Affected cases have autosomal-dominant thrombocytopenia but no other hematological features.