Congenital thrombotic thrombocytopenic purpura (cTTP) is an ultra-rare thrombomicroangiopathy caused by an inherited deficiency of a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13). There are limited data on genotype-phenotype correlation; there is no consensus on treatment. We reviewed the largest cohort of cTTP cases, diagnosed in the United Kingdom, over the past 15 years. Seventy-three cases of cTTP were diagnosed, confirmed by genetic analysis. Ninety-three percent were alive at the time of review. Thirty-six percent had homozygous mutations; 64% had compound heterozygous mutations. Two presentation peaks were seen: childhood (median diagnosis age, 3.5 years) and adulthood, typically related to pregnancy (median diagnosis age, 31 years). Genetic mutations differed by age of onset with prespacer mutations more likely to be associated with childhood onset (P = .0011). Sixty-nine percent of adult presentations were associated with pregnancy. Fresh-frozen plasma (FFP) and intermediate purity factor VIII concentrate were used as treatment. Eighty-eight percent of patients with normal blood counts, but with headaches, lethargy, or abdominal pain, reported symptom resolution with prophylactic therapy. The most common currently used regimen of 3-weekly FFP proved insufficient for 70% of patients and weekly or fortnightly infusions were required. Stroke incidence was significantly reduced in patients receiving prophylactic therapy (2% vs 17%; P = .04). Long-term, there is a risk of end-organ damage, seen in 75% of patients with late diagnosis of cTTP. In conclusion, prespacer mutations are associated with earlier development of cTTP symptoms. Prophylactic ADAMTS13 replacement decreases the risk of end-organ damage such as ischemic stroke and resolved previously unrecognized symptoms in patients with nonovert disease.

The cornerstone of life-saving therapy in immune mediated thrombotic thrombocytopenic purpura (iTTP) has been plasma exchange (PEX) combined with immunomodulatory strategies. Caplacizumab, a novel anti-von Willebrand factor nanobody, trialled in two multicentre, randomised-placebo-controlled trials leading to EU and FDA approval, has been available in the UK through a patient-access scheme. Data was collected retrospectively from 2018-2020 for 85 patients receiving caplacizumab, including 4 children, from 22 UK hospitals. Patient characteristics and outcomes in the real-world clinical setting were compared with caplacizumab trial endpoints and historical outcomes in the pre-caplacizumab era. 84/85 patients received steroid and rituximab alongside PEX; 26% required intubation. Median time to platelet count normalisation (3 days), duration of PEX (7 days) and hospital stay (12 days) was comparable with RCT data. Median duration of PEX and time from PEX initiation to platelet count normalisation was favourable compared with historical outcomes (p<0.05). TTP recurrence occurred in 5/85 patients; all with persistent ADAMTS13 activity <5iu/dL. Of 31 adverse events in 26 patients, 17/31 (55%) were bleeding episodes and 5/31 (16%) were thrombotic events (two unrelated to caplacizumab); mortality was 6% (5/85), with no deaths attributed to caplacizumab. In 4/5 deaths caplacizumab was introduced >48 hours after PEX initiation (3-21 days). This real-world evidence represents the first and largest series of TTP patients receiving caplacizumab outside clinical trials, including paediatric patients. Representative of true clinical practice, the findings provide valuable information for clinicians treating TTP globally.

Patients with mild haemophilia A may have a discrepancy in the factor VIII (FVIII) level when measured with a one-stage assay (FVIII:C1) compared with a two-stage assay (FVIII:C2). This discrepancy usually results in the one-stage level being higher than the two-stage level. A F8 mutation resulting in a Tyr346-->Cys substitution within the a1 interdomain region has been described which results in the converse assay discrepancy. We report four individuals (three families) who have this mutation. Mean FVIII:C1 level was 25 IU dL(-1) compared with a mean FVIII:C2 level of 63 IU dL(-1). These individuals had presented opportunistically and did not have a clinically significant bleeding disorder. The bleeding phenotype correlated with the two-stage assay result rather than the one-stage result. FVIII replacement therapy does not appear to be required for these individuals.

The Multiplate device gives reproducible, precise results in volunteers and stroke/TIA patients.