CELLULAR IMMUNOTHERAPY TARGETING CLL-1 FOR JUVENILE MYELOMONOCYTIC LEUKEMIA

Background: CBL syndrome is a rare RASopathy, characterized by increased risk of JMML, vasculitis, autoinflammation and immunitary alterations.While bleeding disorders are recognized in other RASopathies, data specific to CBL syndrome are lacking.This study aims to describe the coagulation abnormalities and bleeding manifestations in patients with germline heterozygous CBL mutations.Methods: A European survey was conducted across centers in Italy, France, and Spain.Data were collected from patients with confirmed germline heterozygous CBL mutations.The survey included basic coagulation parameters and documentation of clinical bleeding symptoms.Results: Fifteen patients with CBL syndrome were included.Among the 14 patients evaluated for activated partial thromboplastin time (aPTT), 86% (12/14) showed mildly prolonged aPTT values (median 1.39; range 1.05-2.03).The international normalized ratio (INR) was mildly elevated in 46% (5/11) of tested patients (median 1.23; range 0.96-1.54).All individuals tested demonstrated reductions in multiple coagulation factors, including II, V, VII, VIII, IX, X, XI, and XII.Of 7 patients assessed for von Willebrand factor (vWF), 5 exhibited mild reductions, although complete vWF profiling was not available for most.A clinically relevant bleeding tendency, including prolonged bleeding after dental extraction and menorrhagia, was observed in 20% of the cohort.Conclusions: This preliminary survey reveals frequent mild coagulation abnormalities and a non-negligible bleeding phenotype in CBL syndrome patients, highlighting the need for more comprehensive assessments in larger cohort.The underlying mechanisms remain to be clarified and may include platelet dysfunction, subclinical endothelial damage, and impaired hepatic synthesis.