The relationship between myelodysplasia and autoimmunity is supported by their epidemiologic association, the existence of common immune-mediated physiopathologic mechanisms, and the response to similar immunosuppressive therapies.1 Idiopathic cytopenia of uncertain significance (ICUS) and idiopathic dysplasia of uncertain significance (IDUS) are two recently recognized provisional conditions characterized by isolated/unexplained cytopenia and/or dysplasia in <10% bone marrow cells.2, 3 Here we report five paradigmatic cases of refractory/relapsing autoimmune cytopenias, namely autoimmune hemolytic anemia (AIHA), immune thrombocytopenia (ITP), and chronic idiopathic neutropenia (CIN), that evolved to IDUS/bone marrow failure syndromes over time. Figure 1 (left panel) show the clinical course and the hematologic parameters of 4 of the cases: Case 1 (AIHA, F, 61 years at diagnosis, with clear evidence of bone marrow erythrocyte precursor hyperplasia). responded to steroids, but relapsed during tapering, and was treated therefore with low-dose rituximab, with no response. A subsequent bone marrow evaluation showed 25%-30% cellularity with mild erythroid and megakaryocyte dysplasia, and normal cytogenetics, consistent with the diagnosis of IDUS. Thereafter she developed transfusion dependence and reticulocytopenia with the presence of anti-erytroblast antibodies. Bone marrow re-evaluation showed marked hypocellularity (10%) consistent with the diagnosis of aplastic anemia (AA). She underwent immune-suppressive therapy with steroids, cyclosporin and rabbit-ATG with partial and transient response, followed by a second horse-ATG course, again with a transient response. Case 2 (ITP, M, 57 years at diagnosis) was treated with steroids, azathioprine (as steroid-sparing agent), and then splenectomized, with a transient partial response. He was responsive to IvIg monthly pulses only. Two subsequent bone marrow evaluations showed megakaryocyte hyperplasia with dysplastic features (Figure 1, right panel A and B), and normal cytogenetics, consistent with the diagnosis of IDUS. The patient started thrombopoietin (TPO)-receptor agonists (romiplostim, followed by eltrombopag), with transient partial response, still requiring IvIg pulses and/or platelets transfusions for bleeding. Case 3 (F, 52 years at diagnosis) had a history of relapsing, steroid-dependent ITP, already treated with splenectomy and under azathioprine at referral. Bone marrow evaluation showed megakaryocyte hyperplasia with dysplasia and normal karyotype (IDUS). The patient stopped azathioprine and started eltrombopag, with clinical response on bleeding symptoms. However, IvIg pulses and/or platelets transfusions were administered for occasional platelets drop <5 × 109/L. The last marrow evaluation (Figure 1, right panel C and D) showed 40%-50% cellularity, with megakaryocyte and erythroid dysplasia, and the presence of an interstitial T lymphoid infiltrate. Case 4 (F, 46 years) was initially diagnosed with Evans’ syndrome, with marrow features of megakaryocyte and erythroid hyperplasia, and normal cytogenetics. After initial response to steroids, blood counts worsened at tapering, and cyclosporine was added as steroid-sparing agent. Bone marrow re-evaluation showed 10% cellularity, marked myeloid and erythroid hypoplasia, consistent with the diagnosis of AA. A first course with rabbit-ATG and a second with horse-ATG were administered, with sustained/partial response on platelet counts, and a delayed response (2 years) on transfusion-dependent anemia. Case 5 (F, 41 years) was diagnosed in 2001 with CIN, with positive anti-neutrophil antibodies and normal bone marrow evaluation, including karyotype. The patient was followed for about 9 years, with neutrophil counts 0.13 − 0.20 × 103/mmc, and no significant clinical events. Bone marrow re-evaluation (2015) showed hypocellularity with markedly hypoplasic granulopoietic lineage, dyserythropoiesis and dysmegakaryopoiesis. Interestingly, immunohistochemical staining demonstrated an interstitial and nodular infiltration of cytotoxic T-cells, suggesting the existence of an immune effect against myeloid precursors (Figure 1, right panel, E–H) Hematologic values and treatment (left panel), and marrow trephine biopsies (right panel) of autoimmune cytopenias evolved to ICUS/IDUS or other bone marrow failure syndromes. (Left panel) shaded areas indicate steroid treatment, methylprednisolone 1 mg/kg/day for 20–30 days subsequently tapered; LD-R: rituximab given at fixed low dose of 100 mg/week x4; ATG: anti-thymocyte globulin; CyA: cyclosporine; AZA: azathioprine; TPO-m: thrombopoietin mimetics (romiplostim – eltrombopag); ↓: RBC transfusion; ⇓: platelet transfusion; ∇: IvIg; BM: bone marrow evaluation. An expert hemopathologist reviewed all bone marrow trephine biopsies (right panel) before and after disease progression/evolution and performed further immune-hysto-chemestry testing where indicated. Case 2 shows some degree of dysmyelopiesis in the form of megakaryocytes clustering in loose aggregates, sometime with dysmorphic and hypolobulated nuclei (A) together with morphological abnormalities of the erythropoietic series characterized by megaloblastic changes, increased number of proerytroblasts and morphological abnormalities of the erythroblasts (B). Case 3 shows interstitial infiltration of lymphoid T-cells, identified by immunohistochemical staining for the anti-CD3 antibody (C), and morphological abnormalities of the megakaryocytes forming loose clusters of hypolobulated elements (D). Case 5 shows markedly hypoplasic granulopoietic lineage, as highlighted by the myeloperoxidase immunostaining (E); megakaryocytes form loose clusters of mainly hypolobulted forms (F). CD3 (G) and CD8 (H) immunohistochemical staining demonstrate interstitial and nodular T-cells lymphoid infiltration These cases share common features, including a chronic disease history lasting several years, clearly starting with immune destruction of peripheral blood cells with evidence of bone marrow compensatory activity and no dysplastic features. The presence of an autoimmune reaction against bone marrow precursors has been already shown in peripheral autoimmune cytopenias. In AIHA an anti-erythroblast reactivity leading to apoptosis of erythroid precursors has been reported, and associated with reticulocytopenia, a known clinical emergency with an extremely high transfusion need.4 In ITP, the impaired megakaryopoiesis has been attributed to autoantibodies cross-reacting against platelet glycoproteins and to increased levels of the suppressive cytokine TGF-β, and its crucial role has been strengthened by the clinical efficacy of TPO-receptor agonists. Likewise, in CIN there is evidence of several immunologic mechanisms affecting bone marrow granulopoiesis, including the detection of activated T lymphocytes, and inflammatory and proapoptotic cytokines. The presence of a “central” autoimmunity, i.e. anti-erythroblast antibodies, has been reported also in a half of patients with refractory anemia (with or without ring sideroblasts), along with increased caspase-3 activity, elevated levels of the pro-apoptotic protein Bax, and decreased Bcl-2 expression confirming that apoptosis is the hallmark of low-risk MDS.5 In the cases of autoimmune cytopenias described here, we hypothesize a shift from autoimmunity against circulating blood cells to bone marrow precursors, leading to insufficient marrow compensatory response, progressive/variable degree of marrow dysplasia, and ultimately overt bone marrow failure. Although it cannot be excluded that cytotoxic drugs may have induced some dysplastic features in patient 2 and 3, this is not the case of the other subjects, who only received steroids or rituximab before evolution. An attractive hypothesis is that ICUS/IDUS represent a mild form of the spectrum of bone marrow failure syndromes, i.e. a shadowland where the prevalent immunopathologic mechanism is directed against bone marrow precursors rather than peripheral erythrocytes, platelets or granulocytes. These conditions are difficult to recognize since the identification of dysplasia is not always reproducible among even experienced hematopathologists. So far, only small numbers of cases of ICUS/IDUS have been published, and little is known about their physiopathology, natural history, and predictors of outcome. Kwok et al.6 prospectively investigated 144 patients with unexplained cytopenias, and showed that bone marrow evaluation led to the diagnosis of MDS in 17%, IDUS in 15%, and ICUS in 69% of cases. There is increasing interest on the presence of somatic mutations, which are observed in a fraction of ICUS/IDUS cases, mostly involving TET2 and DNMT3A.3 Likewise, mutated genes (mostly PIGA, BCOR/BCORL1, DNMT3A, and ASXL1) have been reported in 20%-50% of AA patients, and their presence is associated with a 40% risk of transformation to MDS. As regards PIGA mutations, small PNH-cell clones have been detected in more than 50% of AA and 20% of low-risk MDS patients. It has been hypothesized that GPI-deficient cells display resistance to the T-cell-mediated immune attack and may further expand and differentiate contributing to hemopoiesis at a varying degree. Interestingly, PNH-cells have been detected in CIN and in hypomegakaryocytic thrombocytopenia, further underlining common immune-mediated mechanisms between autoimmune cytopenias and low-risk MDS. Further prospective studies in larger series of autoimmune cytopenias and IDUS/ICUS are needed to unravel the predictive role of molecular lesions in the development of refractoriness to therapy and/or in hematologic evolution. Disclosure statement: Authors have no affiliations that they consider to be relevant and important with any organization that to any author's knowledge has a direct interest, particularly a financial interest, in the subject matter discussed.
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