Bone Marrow Failure Syndromes: (Fig 1), and What They Comprise • Absence of Abnormal Cells in the Bone Marrow Failure Syndromes Are Bone Marrow

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11 Storen EC, Tefferi A. Long-term use of ana- Bone marrow failure cate MDS, but it is now clear that grelide in young patients with essential abnormal clones as well as PNH clones thrombocythemia. Blood 2001;97:863-6. may be present in aplastic anaemia or 12 Harrison CN, Campbell PJ, Buck G, syndromes Wheatley K et al. A randomised compar- arise during the course of the illness and ison of hydroxyurea and anagrelide in high- then disappear.2 risk essential thrombocythemia: the Judith CW Marsh MD FRCP FRCPath, Medical Research Countil PT-1 Trial. Professor of Clinical Haematology and NEngl J Med (in press). Aplastic anaemia 13 Tefferi A. Myelofibrosis with myeloid meta- Honorary Consultant Haematologist, plasia. Review. N Engl J Med 2000;342: Division of Cellular and Molecular Medicine, Definition, disease severity and 1255–65. St George’s University of London; causes 14 Tefferi A, Mesa RA, Nagorney DM, Department of Haematology, St George’s Schroeder G, Silverstein MN. Splenectomy Hospital, London Aplastic anaemia is defined by: in myelofibrosis with myeloid metaplasia; a pancytopenia single-institution experience with 223 • Clin Med 2005;5:332–36 hypocellular bone marrow where patients. Blood 2000;95:2226–33. • normal haemopoietic cells are replaced by fat cells and there is no increase in reticulin or fibrosis Bone marrow failure syndromes: (Fig 1), and what they comprise • absence of abnormal cells in the Bone marrow failure syndromes are bone marrow. characterised by the primary failure to There are three grades of severity of produce one or more blood cell lineages. aplastic anaemia, as defined by peri- Secondary causes of marrow failure such pheral blood counts and the degree of as chemotherapy or radiotherapy, marrow hypocellularity. In non-severe marrow infiltration or peripheral auto- aplastic anaemia the neutrophil count is immune destruction of blood cells are >0.5 × 109/l, in severe aplastic anaemia excluded. Marrow failure may occur at <0.5 × 109/l, and in very severe aplastic the level of the haemopoietic stem cell anaemia <0.2 × 109/l.3 resulting in aplastic anaemia or at a later Aplastic anaemia is a rare idiosyncratic developmental stage of haemopoiesis disorder, with an incidence in the West of affecting a single lineage. Single lineage 1–2 per million population per annum. marrow failure disorders may later It is 2–3 times more common in the Far progress to aplastic anaemia. Bone East. The disease is idiopathic in many marrow failure syndromes are most cases but may be drug-induced or occur commonly acquired but there are rare following an episode of acute viral congenital forms.1 hepatitis (Table 1). In aplastic anaemia, there is overlap with clonal disorders such as paroxysmal Pathogenesis nocturnal haemoglobinuria (PNH) and myelodysplastic syndromes (MDS, Aplastic anaemia is characterised by a pre-leukaemia). Previously, abnormal defect in the haemopoietic stem cell cytogenetic clones were thought to indi- compartment, with both deficiency and

Key Points

Aplastic anaemia is a potentially life-threatening disorder, but treatment outcomes with bone marrow transplantation and immunosuppressive therapy have improved considerably with time

In many patients there is evidence of an autoimmune basis for acquired bone marrow failure disorders

The genetic basis of congenital forms of bone marrow failure is now more clearly understood

KEY WORDS: amegakaryocytic thrombocytopenia, aplastic anaemia, cyclic neutropenia, pure red cell aplasia, severe congenital neutropenia

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(a) (b) There is a risk of spontaneous life-threatening haemorrhage such as cerebral haemorrhage. A careful drug and occu- pational history should be obtained. Children and young adults should be examined for features of congenital aplastic anaemia such as short stature, skeletal anomalies, hypo- or hyper- pigmentation of the skin. Examples of congenital aplastic anaemia are Fanconi anaemia and dyskeratosis congenita.1

Investigations

The following investigations should be performed: • full blood count and blood film Marrow cavity Bone trabeculae (pancytopenia with no abnormal Fig 1. Normal and severe aplastic anaemia bone marrow biopsies. Histological cells such as blasts) sections (a) normal bone marrow with a normal proportion of haemopoietic cells • reticulocyte count interspersed with fat cells in the marrow cavity; (b) bone marrow from a patient with (reticulocytopenia) severe aplastic anaemia showing virtual absence of haemopoietic cells in the marrow cavity and replacement with fat cells. • bone marrow aspirate and trephine biopsy (hypocellular bone marrow defective function. The marrow Clinical presentation with no evidence of infiltration or microenvironment functions normally, blasts or increased fibrosis) Patients present with symptoms of as assessed by long-term marrow cul- marrow cytogenetics (to detect an anaemia or thrombocytopenia or bacte- • ture.4 Aplastic anaemia occurs as an idio- abnormal clone) rial infection due to neutropenia. syncratic reaction and there is increasing flow cytometry of Purpura, bruising, gum bleeding, epis- • evidence for an autoimmune basis to the glycosyl-phosphatidyl taxes and menorrhagia are common. disease (Table 2; Fig 2).5–7 inositol-anchored proteins on blood cells (deficient expression on red cells, neutrophils and monocytes Table 1. Aetiology of acquired aplastic anaemia. indicates a PNH clone) Idiopathic 70–80% of cases • liver function tests and viral Drugs* Antibiotics: chloramphenicol (no evidence for chloramphenicol eye drops), hepatitis screen (to exclude sulphonamides posthepatitic aplastic anaemia) Antirheumatics: gold, penicillamine Anti-inflammatory drugs: phenylbutazone, indomethacin, diclofenac, • serum vitamin B12 and folate (to naproxen, piroxicam exclude severe megaloblastic Anticonvulsants: phenytoin, carbamazepine anaemia which may cause Antithyroids: carbimazole (more likely to cause neutropenia), thiouracil pancytopenia) Antidepressants: dothiepin, phenothiazines Antidiabetics: chlorpropamide • autoimmune profile (systemic lupus Antimalarials: quinine erythematosus is a rare cause of Chemicals Benzene aplastic anaemia) Pesticides: organochlorines (eg lindane, organophosphates) for children and young adults below Cutting oils and lubricating agents • Recreational drugs: methylenedioxy-methamphetamine (MDMA, ecstasy) 35 years old, exclude congenital Viruses Viral hepatitis: non-A, non-B, non-C and non-G in most cases aplastic anaemia – in Fanconi EBV rarely anaemia there are increased PNH Haemolytic PNH in 5%; small PNH clone can be detected by flow cytometry spontaneous and in at least 20–25% of AA patients at presentation diepoxybutane-induced Rarely SLE, pregnancy, anorexia nervosa, thymoma chromosome breakages in cultured peripheral blood lymphocytes, and * Drugs currently licensed in the UK reported to have a rare association with aplastic anaemia (AA). many cases of dyskeratosis congenita EBV = Epstein-Barr virus; PNH = paroxysmal nocturnal haemoglobinuria; SLE = systemic lupus erythematosus. show mutations of the telomerase gene complex.8

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Treatment Table 2. Pathogenesis of aplastic anaemia.

Supportive care. Initial treatment is to Evidence stabilise the patient clinically with blood Haemopoietic stem cell defect Autoimmune basis to the disease and platelet transfusions and to admin- ister broad-spectrum intravenous antibi- Bone marrow colony forming cells of all HLA restriction: over-representation of otics for fevers. When the platelet count cell lineages reduced or absent HLA-DR15 is below 10 × 109/l prophylactic platelets Long-term marrow cultures show reduced Syngeneic BMT unsuccessful in at least should be given and prophylactic anti- marrow repopulating ability 50% of patients unless prior biotics and antifungal drugs if there is immunosuppression given severe neutropenia. HLA antibodies may Reduced or absent long-term culture 60–80% patients respond to initiating cells (LTC-IC) in bone marrow immunosuppressive therapy using ATG complicate transfusions, necessitating and ciclosporin 3 HLA-matched platelet transfusions. Reduced % bone marrow haemopoietic Increased levels of cytokines that inhibit progenitor (CD34+) cells compared with haemopoiesis (IFN-γ, TNF-α) and Bone marrow transplantation. Early bone normal bone marrow upregulate Fas-antigen expression in marrow transplantation (BMT) from an blood and marrow HLA identical sibling is indicated as Bone marrow CD34+ cells are more Increased Fas-antigen expression on bone first-line therapy if the patient has severe apoptotic than normal CD34+ cells marrow CD34+ cells or very severe disease and is younger Bone marrow cells have shortened telomere Activated cytotoxic CD8 T cells present in lengths compared with normal bone marrow blood and bone marrow than 40 years of age.9 An immunosup- cells T cell repertoire analysis shows oligoclonal pressive, non-myeloablative preparative expansion of CD8 T-cells regimen is used to help prevent graft Upregulation of apoptosis and immune rejection (cyclophosphamide 200 mg/kg response genes with antithymocyte globulin (ATG)). ATG = antithymocyte globulin; BMT = bone marrow transplantation; IFN = interferon; LTC-IC = long-term Ciclosporin and methotrexate are used culture initiating cells; TNF = tumour necrosis factor. to prevent graft versus host disease. Irradiation is not necessary, so children grow and develop normally post-BMT to respond to immunosuppressive donor. Although 60–80% will respond and fertility is well preserved. The suc- therapy (see below).3,11 and achieve normal or near-normal cess rate is good, with a 70–90% chance blood counts, recovery is unstable. of long-term cure for those patients Immunosuppressive therapy. Immuno- Relapse may occur in 10–30%, necessi- younger than 40 years of age (Fig 3).10 suppression, using the combination of tating further immunosuppression, BMT from an HLA matched volunteer ATG and ciclosporin, is indicated for all approximately 10% later develop donor (MUD BMT) may be considered patients over 40 years old, all those with haemolytic PNH, and a further 10% for those patients with severe or very non-severe disease and for younger MDS or acute myeloid leukaemia. severe disease who do not have an HLA patients with severe or very severe disease Nevertheless, a good quality of life is compatible sibling and who have failed who lack an HLA compatible sibling possible for most patients.12

Fig 2. Immune-mediated aplastic anaemia (AA). In AA, activated cytotoxic T cells secrete cytokines such as tumour necrosis factor Fas (TNF)-α and interferon (IFN)-γ which ligand TNF inhibit haemopoietic progenitor Cytoxic cells (HPC). TNF- and IFN- IFN-γ α γ T lymphocyte IFN-γ upregulate the expression of the Haematopoietic cell Fas receptor on HPCs, triggering TNF IRF-1 apoptosis. Increased production of Interleukin-2 interleukin-2 results in expansion of TNF receptor T cells. TNF-α and IFN-γ also NOS Transcription increase nitric oxide synthase (NOS) IFN-γ receptor Cell cycling and nitric oxide (NO) production by Clonal Fas NO marrow cells, which may contribute expansion receptor Apoptosis of T-cells to immune-mediated cytotoxicity 5 and elimination of HPCs (IRF-1 = Toxicity for IFN regulatory factor-1) other cells (reproduced, with permission, from Ref 7).

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Fig 3. Actuarial survival for patients undergoing HLA 1.0 identical sibling bone marrow ≤10 years: n = 156, 89% (83–94%) transplantation for severe 10–20 years: n = 335, 87% (83–98%) aplastic anaemia according to 21–30 years: n = 226, 77% (71–82%) age.10 0.8 31–40 years: n = 126, 68% (59–77%)

0.5 >40 years: n = 111, 47% (35–58%)

Probability of survival 0.3

0.0 0 365730 1,095 1,460 1,825 2,190 2,555 2,920 3,285 Time after treatment (days)

Pure red cell aplasia It is important to distinguish acquired thymectomy. Some cases are drug- PRCA from the rarer congenital form, induced.13 Severe PRCA due to recombi- Definition, mechanisms and Diamond Blackfan anaemia (DBA), in nant human erythropoietin (EPO) has aetiology young patients. DBA is often associated recently been reported, in most cases There is defective maturation of red cell with short stature and skeletal anomalies, with epoetin-alpha (Eprex®) when given precursors in pure red cell aplasia typically the red cell adenine deaminase subcutaneously in chronic kidney dis- (PRCA), with failure to produce reticulo- level is elevated and mutations in the ease. This is associated with anti-EPO cytes and hence mature red cells. The ribosomal protein S19 (RPS19) gene are antibodies and appears to have been due block in maturation may occur at the found in 25% of affected individuals. A to changes in the formulation of the level of early (burst-forming unit second DBA gene has been located on drug.14 (BFU-E)) or late (colony-forming unit chromosome 8.1 (CFU-E)) erythroid progenitors, Many cases of acquired PRCA are idio- Investigations resulting in an absence of erythroid pre- pathic and immune in origin (Table 3). cursors in the bone marrow, or at the PRCA often occurs in association with The following investigations should be early normoblast stage producing a mat- other systemic autoimmune disorders. It performed: uration arrest in the bone marrow with is associated with a thymoma in 10–15% • full blood count and blood film absence of late normoblasts. of cases, 50% of whom will respond to (normocytic, normochromic anaemia) • reticulocyte count (severe Table 3. Conditions associated with acquired pure red cell aplasia (PRCA). reticulocytopenia) bone marrow aspirate and trephine Aetiology Mechanisms • biopsy (absent red cell precursors or Idiopathic Immune-mediated maturation arrest (see above); SLE, RA, Sjögren’s disease Immune-mediated examine for a secondary cause of Thymoma (sometimes with myasthenia Immune-mediated PRCA such as lymphoma, chronic gravis and/or hypo-γ-globulinaemia) lymphocytic leukaemia, MDS; Drugs: phenytoin, isoniazid, azathioprine Marrow toxicity, drug-dependent antibodies immunophenotyping and gene EPO in chronic kidney disease Anti-EPO antibodies rearrangement studies for heavy B cell lymphoproliferative disorders Immune-mediated chain and T cell receptor (eg CLL, lymphoma) monoclonal expansion) Parvovirus B19 infection Lysis of late erythroid progenitors (CFU-E) with chest X-ray and computed CMV, EBV rarely parvovirus infection • tomography scan of thorax (to Myelodysplastic syndrome Mechanism of PRCA uncertain: ? extreme apoptosis of red cell progenitors exclude thymoma) autoimmune profile CFU = colony forming unit; CLL = chronic lymphocytic leukaemia; CMV = cytomegalovirus; EBV = • Epstein-Barr virus; EPO = erythropoietin; RA = rheumatoid arthritis; SLE = systemic lupus erythematosus. • parvovirus B19, cytomegalovirus and Epstein-Barr virus serology.

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Treatment resulting in periodic neutropenia, often Study Group. Antithymocyte globulin with severe, usually occurring every 21 days. or without cyclosporin A: 11-year follow-up Blood transfusions are required until of a randomized trial comparing treatments Severe infections may occur during the recovery occurs. Thymectomy should be of aplastic anemia. Blood 2003;101:1236–42. neutrophil nadir. Most patients with considered in patients with a thymoma 13 Charles RJ, Sabo KM, Kidd PG, Abkowitz cyclic neutropenia and SCN respond to JL. The pathophysiology of pure red cell and intravenous immunoglobulin is granulocyte-colony stimulating factor.17 aplasia: implications for therapy. Blood indicated for parvovirus-induced PRCA. 1996;87:4831–8. For the remaining patients, immunosup- 14 Bennett CL, Luminari S, Nissenson AR, pressive therapy is given, initially pred- References Tallman MS et al. Pure red-cell aplasia and nisolone starting at 1 mg/kg/day for epoetin therapy. N Engl J Med 2004;351: 1Dokal I. Inherited aplastic anaemia/bone 1403–8. four weeks, to which 50% of patients will marrow failure syndromes. In: Hoffbrand 15 Robak T. Monoclonal antibodies in the respond. For non-responders, ciclo- AV, Tuddenham E, Catovsky D (eds). treatment of autoimmune cytopenias. sporin or azathioprine are often used. Postgraduate haematology, 5th edn. Oxford: Review. Eur J Haematol 2004;72:79–88. Monoclonal antibody therapy with Blackwell Publishing, 2005. 16 Drachman JG. Inherited thrombocy- anti-CD20 (rituximab) and anti-CD52 2Socie G, Rosenfeld S, Frickhofen N, topenia: when a low platelet count does not Gluckman E, Tichelli A. Late clonal diseases mean ITP. Review. Blood 2004;103:390–8. (alemtuzumab) is being evaluated for of treated aplastic anemia. Review. Semin 17 Ancliff PJ, Gale RE, Liesner R, Hann IM, 15 refractory cases. Hematol 2000;37:91–101. Linch DC. Mutations in the ELA2 gene 3Marsh JC, Ball SE, Darbyshire P, encoding neutrophil elastase are present in Gordon-Smith EC et al. British Committee most patients with sporadic severe congen- Amegakaryocytic for Standards in Haematology. Guidelines ital neutropenia but only in some patients thrombocytopenia for the diagnosis and management of with the familial form of the disease. Blood acquired aplastic anaemia. Br J Haematol 2001;98:2645–50. Acquired amegakaryocytic thrombo- 2003;123:782–801. cytopenia is a rare cause of severe 4Marsh JC, Testa NG. Stem cell defect in thrombocytopenia and bleeding. Mega- aplastic anaemia. In: Schrezenmeier H, Bacigalupo A (eds). Aplastic anaemia. karyocytes are absent from the bone pathophysiology and treatment. Cambridge: marrow, in contrast to immune throm- Cambridge University Press, 2000:3–20. bocytopenia where megakaryocyte num- 5Young NS, Maciejewski J. The pathophysi- bers are normal or increased. Patients ology of acquired aplastic anemia. Review. may later develop aplastic anaemia or N Engl J Med 1997;336:1365–72. 6Risitano A, Maciejewski JP, Green S, MDS. Regular platelet transfusions are Plasilova M et al. In-vivo dominant required; some patients respond to ATG immune responses in aplastic anaemia: and ciclosporin. The underlying defect in molecular tracking of putatively patho- most cases of congenital amegakary- genetic T-cell clones by TCR beta-CDR3 ocytic thrombocytopenia is due to a sequencing. Lancet 2004;364:355–64. 7Young NS. The etiology of acquired aplastic mutation in the thrombopoietin receptor anaemia. Rev Clin Exp Haematol 2000; 1 (c-mpl). Thrombocytopenia with 4:236–59. absent radii is another example of con- 8Vulliamy T, Marrone A, Szydlo R, Walne A genital thrombocytopenia associated et al. Disease anticipation is associated with with absent or reduced megakaryocytes, progressive telomere shortening in families 16 with dyskeratosis congenita due to muta- but the gene defect in unknown. tions in TERC. Nat Genet 2004;36:447–9. 9Bacigalupo A, Brand R, Oneto R, Bruno B et al. Treatment of acquired severe aplastic Severe congenital neutropenia anemia: bone marrow transplantation com- and cyclic neutropenia pared with immunosuppressive therapy – The European Group for Blood and Severe congenital neutropenia (SCN) is a Marrow Transplantation experience. rare inherited or sporadic form of Review. Semin Haematol 2000;37:69–80. marrow failure, with maturation arrest at 10 Marsh JCW. Management of acquired the promyelocyte-myelocyte stage in the aplastic anaemia. Blood Rev 2005;19: 143–51. bone marrow. It presents in early infancy 11 Bacigalupo A, Locatelli F, Socie G, Dini G with severe neutropenia and recurrent et al. Fludarabine, cyclophosphamide and bacterial infections. The autosomal anti-thymocyte globulin (ATG) for alterna- recessive form is known as Kostmann’s tive donor transplants in acquired aplastic syndrome. Mutation in the neutrophil anaemia (SAA): a report from the EBMT-SAA Working Party. Bone Marrow elastase gene (ELA2) occurs in many Transpl 2002;29:312a. affected children and in all patients with 12 Frickhofen N, Heimpel H, Kaltwasser JP, cyclic neutropenia – a stem cell disorder Schrezenmeier H; German Aplastic Anemia

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