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Although two clusters have been identified in France, constitutional factor XI deficiency is a rare disorder. Acquired factor XI deficiency is extremely rare. The management of factor XI deficiency is not staightforward because of the unpredictable bleeding tendency that does not clearly relate to the factor XI level. Other haemostastis parameters have to be taken into account to evaluate the bleeding tendency. We report the cases of a congenital factor XI deficiency, an acquired factor XI deficiency and a von Willebrand disease associated to a factor XI deficiency. On the other hand, some interferences can lead to underestimation of factor XI and we report the case of an interference by lupus anticoagulant. The objective of this review is to better understand how to manage a reduced factor XI level.

During a blood test, the discovery of thrombocytosis is a frequent phenomenon with multiple origins. False thrombocytosis linked to analytical interferences is rare but must be eliminated before confirming the anomaly. The reaction origin, often very easily demonstrated by the context and/or the presence of a biological inflammatory syndrome, is the most frequent. More rarely, the diagnosis is oriented towards a clonal hematological pathology not limited to essential thrombocythemia. Currently, many biological tools, which have largely contributed to the recommendations of the latest WHO classification of chronic myeloid neoplasms, are available to classify these pathologies as precisely as possible, allowing optimal management.

Sideroblastic anemias in adults are often quickly labeled as myelodysplasias. We report two unfrequent observations of secondary acquired forms. The first one is a 15-year-old girl presented with severe cytopenias. The myelogram revealed the presence of vacuolated myeloid and erythroblastic precursors, with ring sideroblasts. Copper deficiency has been demonstrated in front of the association with collapsed cupremia and ceruleoplasminemia, with normal cupruria. The second case is a 70-year-old man, treated for 1 month with several lines of antibiotics for a skin infection, referred for cytopenias. The myelogram found vacuolated erythroblastic precursors and ring sideroblasts. Linezolid's responsibility has been proposed, with a favorable development after treatment has been stopped. These two observations, which describe unfrequent sideroblastic anemias, point out that this discovery should not lead to the diagnosis of myelodysplasia before having considered the many other etiologies.

The discovery of eosinophilia above 1.5 G/L should not be considered innocuous, requiring monitoring for etiology and possible secondary organ damage. Among these, cardiac localization is the most worrying, sometimes indolent, to be systematically sought by ultrasound and magnetic resonance. The potential etiologies are very numerous, mostly reactive and corticosensitive, much more rarely clonal in relation to a malignant hemopathy usually chronic and myeloid, sometimes sensitive to tyrosine kinase inhibitors.

Immunosuppression is a well known risk factor for the development of lymphoid pathologies. The classification of these neoplasias is becoming more precise and complex, some features being common to all immunocompromised patients, primarily the important influence of Epstein-Barr virus. Whatever the origin of the immunodepression, these lymphoid proliferations are very heterogeneous, constituting a wide range between polymorphic aspects and clearly lymphomatous morphologies indistinguishable from those observed in immunocompetent subjects. It is important to detect precisely these different categories of proliferation within each group of immunosuppression, to better individualize the prognosis and the management of patients.

The discovery of a monocytosis is a frequent phenomenon, requiring confirmation by reading under a microscope by an experimented biologist, to overcome usual cytological traps such as the presence of hairy cells, promonocytes or monoblasts. In the vast majority of cases the secondary origin is very easily found by the context and/or the presence of a biological inflammatory syndrome. More rarely the diagnosis is directed towards an eosinophilic pathology or an acute leukemia. In other cases, CMML, MPN or MDS with monocytosis may be highlighted. In the absence of any pathognomonic element and the presence of "borderline" forms the differential diagnosis between these 3 entities is not always straightforward, requiring, according to WHO, molecular investigations and elimination of any reactive cause of monocytosis. Although histological, immunohistochemical and phenotypic flow cytometric studies are not currently recommended by WHO, these investigations could be of interest in the evaluation of difficult cases.

Adult neutropenia, defined as a blood neutrophil count below 1.5 G/L, is a common condition. The most common cause of acute neutropenia is a drug-related reaction or an acute infectious disease. In chronic forms many etiologies are possible, sometimes poorly-defined, requiring precise explorations. The purpose of this article is to recall the required criteria for exploring neutropenia and to point out the algorithm of explorations in order to find the cause. Etiologies of acute and chronic forms are also detailed.

The presence of serum monoclonal IgM is often associated with the diagnosis of Waldenström macroglobulinemia (WM) or other chronic lymphoproliferative disorders. IgM myeloma is a rare entity (0.5%). We report the case of an IgM myeloma complicated by systemic amyloidosis AL, with an impure nephrotic syndrome and a factor FX deficiency.

The most frequent causes of hemolytic anemias are immune or infectious diseases, drug induced hemolysis, thrombotic microangiopathies, hereditary spherocytosis, glucose-6-phosphate dehydrogenase or pyruvate kinase deficiencies, thalassemia's and sickle cell disease. Sometimes no cause is found because a rarer etiology is involved. The goal of this review is to remember some unfrequent constitutional or acquired causes and to point out difficulties to avoid wrong interpretations of analysis results.