Background: Bleeding anomalies occur in patients affected by Noonan syndrome. No study has been performed in patients with molecularly confirmed RASopathy. We aimed to characterize the frequency and types of bleeding disorders in patients with RASopathies and evaluate any significant association with laboratory findings.
Patients and methods: Forty-nine individuals (PTPN11, n=27; SOS1, n=7; RIT1, n=3; SPRED1, n=1; LZTR1, N=3; RAF1, n=2; BRAF, n=4; MEK1, n=1; MEK2, n=1), and 49 age- and sex-matched controls were enrolled in the study. The “Paediatric Bleeding Questionnaire Scoring Key” was administered to patients and families. Laboratory screening tests including clotting factors dosing, platelet count, prothrombin time, and partial thromboplastin time, were employed both in patients and controls to characterize the bleeding diathesis. A subgroup of 29/49 patients and 29/49 controls was also tested for platelet function.
Results: Regardless the gene involved, pathological bleeding scores were recorded in 14 (28.5%) patients. Among these, 7 were mutated in PTPN11 (26% of total cases with PTPN11 mutations), 3 in SOS1 (43%), 2 in RIT1 (67%), 1 in BRAF (25%), and 1 in MEK1. Compared to patients with normal bleeding scores, those with pathologic bleeding score showed higher prevalence of splenomegaly (p=0.006), prolonged aPTT (p = 0.04), lower levels of coagulation factor V (FV) (p = 0.001), factor VII (FVII) (p = 0.003), factor X (FX) (p = 0.0008) and factor XIII (FXIII) (p = 0.002), higher vWAg (p = 0.04), and lower platelet sensitivity to Ristocetin (p = 0.001), arachidonic acid (AA) (p = 0.009) and collagen (p = 0.01). The presence of hematomas inversely correlated with FV (p = 0.002), FVII (p = 0.003), FX (p = 0.002) and FXIII (p = 0.004) levels, and directly correlated with platelet response to collagen (p = 0.02) and AA (p = 0.01). The presence of splenomegaly directly correlated with occurrence of hematoma (p=0.006), platelet response to Ristocetin (p = 0.04) and AA (p = 0.04), and inversely correlated with FV levels (p = 0.03).
Conclusions: Patients with RASopaties and a bleeding tendency exhibit multiple coagulation-related laboratory abnormalities, including platelet-related disorders. Splenomegaly is frequently detected and might be a suggestive sign for qualitative platelet dysfunction. A comprehensive clinical assessment should be carried out at diagnosis, during the follow-up and before any surgical procedures. Since there is currently no consensus on management of bleeding complications, it is important that physicians closely monitor these patients.