A focus on dominant negative variants in a series of 170 heterozygous FXI-deficient patients

INTRODUCTION

Dominant-negative effects have been described for 10 F11 variants in the literature.

AIM

The current study aimed at identifying putative dominant-negative F11 variants.

MATERIAL AND METHODS

This research consisted in a retrospective analysis of routine laboratory data.

RESULTS

In a series of 170 patients with moderate/mild factor XI (FXI) deficiencies, we identified heterozygous carriers of previously reported dominant-negative variants (p.Ser243Phe, p.Cys416Tyr, and p.Gly418Val) with FXI activities inconsistent with a dominant-negative effect. Our findings also do not support a dominant-negative effect of p.Gly418Ala. We also identified a set of patients carrying heterozygous variants, among which five out of 11 are novel, with FXI activities suggesting a dominant-negative effect (p.His53Tyr, p.Cys110Gly, p.Cys140Tyr, p.Glu245Lys, p.Trp246Cys, p.Glu315Lys, p.Ile421Thr, p.Trp425Cys, p.Glu565Lys, p.Thr593Met, and p.Trp617Ter). However, for all but two of these variants, individuals with close to half normal FXI coagulant activity (FXI:C) were identified, indicating an inconstant dominant effect.

CONCLUSION

Our data show that for some F11 variants recognized has having dominant-negative effects, such effects actually do not occur in many individuals. The present data suggest that for these patients, the intracellular quality control mechanisms eliminate the variant monomeric polypeptide before homodimer assembly, thereby allowing only the wild-type homodimer to assemble and resulting in half normal activities. In contrast, in patients with markedly decreased activities, some mutant polypeptides might escape this first quality control. In turn, assembly of heterodimeric molecules as well as mutant homodimers would result in activities closer to 1:4 of FXI:C normal range.

Impact of Molecular Biology in Diagnosis, Prognosis, and Therapeutic Management of BCR::ABL1-Negative Myeloproliferative Neoplasm

BCR::ABL1-negative myeloproliferative neoplasms (MPNs) include three major subgroups-polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF)-which are characterized by aberrant hematopoietic proliferation with an increased risk of leukemic transformation. Besides the driver mutations, which are JAK2, CALR, and MPL, more than twenty additional mutations have been identified through the use of next-generation sequencing (NGS), which can be involved with pathways that regulate epigenetic modifications, RNA splicing, or DNA repair. The aim of this short review is to highlight the impact of molecular biology on the diagnosis, prognosis, and therapeutic management of patients with PV, ET, and PMF.

[Eosinophilia heralding the diagnosis of eosinophilic fasciitis (Shulman's disease)]

INTRODUCTION

Eosinophilic fasciitis or Shulman's disease is characterized, in its typical form, by palpable thickening of the skin and soft tissues, blood hypereosinophilia and fascia lesions. We hereby report a case of eosinophilic fasciitis in which hypereosinophilia preceded for several months the clinical signs of fasciitis.

CASE REPORT

A 64-year-old woman, with a history of Little's syndrome with motor disability, was admitted in internal medicine for eosinophilia. For almost three months, no origin to the eosinophilia was found. The secondary onset of an edema and pain located on four limbs led to the diagnosis of eosinophilic fasciitis. Muscle magnetic resonance imaging was supportive and the muscle histological analysis confirmed the diagnosis of eosinophilic fasciitis. Treatment with steroids induced a rapid normalization of the eosinophilia and edema.

CONCLUSION

In this case report, eosinophilia was preceding the clinical cutaneous signs that led to the diagnosis of eosinophilic fasciitis. It is likely to believe that myalgias, frequently found in the onset of eosinophilic fasciitis, may have been hidden by the history of infantile encephalopathy. The diagnosis of eosinophilic fasciitis must be kept in mind of physicians in the investigation of an eosinophilia, even though cutaneous signs are lacking.