Aplastic anemia

Anoop.K.R, MDAssistant Clinical Professor of Medicine

ST

Pt is a 43 year old woman who was in her usual state of health until 03/16/11 when she presented to outside ER with left flank pain and dark urine for two days.

Found to have hct of 26 with platelet count of 26k.

No hemolysis on labs. Peripheral smear reveals no atypical cells with

few large platelets. Initially thought to have ITP- given IVIG x 1. Did not response to IVIG.

Required daily platelet transfusions.

Bone marrow biopsy

markedly hypocellular marrow with 80% fat. Cellularity is composed of entirely maturing erythroid elements. Myeloid elements are markedly decreased. Occasional segmented forms noted. Megakaryocytes rare. Stainable iron increased. No ringed sideroblasts. Reticulin focally increased. No features of parvovirus seen. Several blast forms seen.

Diagnosis of Aplastic Anemia

Marrow is profoundly hypocellular with decrease in all elements.

Residual hematopoietic cells are morphologically normal.

Malignant infiltrates and fibrosis is absent.

Hematopoiesis is non-megaloblastic.

Severity

Moderate aplastic anemia Marrow cellularity <30% Absence of severe pancytopenia Depression of at least two of three blood elements below

normal. Severe

o Bone marrow cellularity <25% or marrow showing <50% normal with two of three peripheral blood count criteria:

o ANC <500 Plt <20k Retic count <40k

Very Severe All of above plus ANC less than 200.

Classification

Inherited Fanconi’s anemia, dyskeratosis congenita, Shwachman-Diamond

Syndrome, Reticular dysgenesis, Amegakaryocytic thrombocytopenia, familial aplastic anemia, preleukemia (monosomy 7) and nonhematologic disease (Down, Dubowitz, Seckel)

Acquired Irradiation drugs and chemicals: cytotoxic agents, benzene, idiosyncratic reaction,

chloramphenicol, NSAIDS, antiepileptics, Gold viruses: EBV, Hepatitis virus (non-A,non-B, non-C, non-G), Parvovirus

(transient aplastic crisis or pure red cell aplasia), HIV Immune diseases: eosinophilic fasciitis, hyperimmunoglobulinemia,

thymoma and thymic carcinoma, GvHD in immunodeficiency PNH Pregnancy Idiopathic

Differential Diagnosis

Pancytopenia with hypocellular bone marrow Acquired aplastic anemia - Inherited aplastic anemia Hypoplastic MDS - Hypoplastic AML

Pancytopenia with cellular bone marrow Primary bone marrow diseases -MDS PNH - Myelofibrosis Myelophthisis - Bone marrow lymphoma Hairy cell leukemia- SLE, Sjogren’s disease Hypersplenism - Vitamin B12 and folate deficiency Overwhelming infection - Alcoholism Brucellosis - Ehrlichiosis Sarcoidosis - tuberculosis

Hypocellular bone marrow with or without cytopenia Q fever - Legionaires disease Mycobacteria - Tuberculosis Hypothyroidism - Anorexia nervosa

Hypocellular AML & hypocellular MDS

Epidemiology

International Aplastic Anemia and Agranulocytosis Study (IAAAS) found 2 confirmed cases per one million people (two PNH units)

Thailand- 4 cases per million

Cumulative survival has increased over the past few decades

Etiology and Pathogenesis

Genetic predisposition found in HLA-DR2.

This correlates to response to immunosuppressants.

Similar results found in hypoplastic MDS.

Pathogenesis

Immune-mediated T-cell destruction of marrow Young demonstrated that removal of

lymphocytes from aplastic bone marrow improved colony number in tissue culture and addition of lymphocytes to normal marrow inhibited hematopoiesis in vitro.

Telomere shortening

Originally thought to be due to stem-cell exhaustion. Telomere shortening also found in X-linked form of

dyskeratosis congenita due to mutations in DKCI. Telomere shortening also found in mutations in TERC

found in AD patients with constitutional Subsequent analysis of patients with acquired aplastic

anemia found mutations in TERC and TERT. Interestingly, family members of patients who share

these mutations can have normal blood counts but hypocellular marrows, reduced CD34 counts and poor hematopoietic colony formations and short telomeres.

Therefore, 1/3 to ½ of patients with aplastic anemia have short telomeres but mutations are only found in 10% of patients.

Treatment

Treatment

ATG: Lymphocyte numbers decreased within the first

few days of therapy and then return to pretreatment levels within a week or so.

Appears to be immunomodulatory as well as lymphocytotoxic- producing a state of tolerance by preferential depletion of activated T cells.

Rabbit appears to be more potent that the horse formulation.

Cyclosporine: its selective effects on T-cell function is due to direct

inhibition on the expression of nuclear regulatory proteins, resulting in decreased T-cell proliferation and activation.

Clinical Endpoints

Response defined as transfusion independence. About 50% response rate with horse ATG.

Relapse defined as requirement of additional immunosuppresants. Happens in 30-40% of patients.

Clonal evolution occurs in 15% of cases. Into MDS, AML, PNH

Improving on ATG & cyclosporine for first line management of AA? Addition of high dose steroids did not improve

outcomes and just added to toxicity. Addition of G-CSF and GM-CSF did not improve

outcomes Addition of mycophenolate did not improve

response rates or outcomes. Sirolimus was equally ineffective. Cyclophosphamide was associated with a higher

death rate due to prolonged neutropenia.

Relapsed/Refractory Aplastic Anemia

Rabbit ATG- if patient has not seen it before and had a decent response to initial treatment.

Alemtuzumab has been shown in the relapsed setting to be effective.

Cyclophosphamide has a 50% response rate in relapsed setting.

Moderate Aplastic Anemia

Role for duclizumab, humanized monoclonal antibody to IL-2 receptor

Role for androgen therapy

HSCT

Definitive therapy for several malignant and non malignant disorders

-autologous : stem cells harvested from the patient

-allogeneic : stem cells collected from a donor

ALLOGENEIC HSCT Ideal donor is a HLA-identical sibling Even minor histocompatibility loci

variations can cause graft rejection/graft versus host disease

ABO blood group compatibility not essential

If HSCT is successful,blood group of recipient changes to that of donor

- myeloablative -> high doses chemotherapy administered to eradicate malignant cells,to clear space for growth of donor stem cells,to suppress host immune response

- non myeloablative -> donor T cells are used to eradicate both malignant and non malignant cells of host origin

Harvesting : -Under GA/spinal.-Repeated aspiration done.-From posterior iliac crests.-Minimum no.of marrow cells required is 1-3 X

10 power 8 cells/kg of recipient’s body weight.

Engraftment : -These donor marrow cells are

transfused through peripheral veins.-Enter into host marrow space and

start engrafting.-2-3 weeks for engraftment to occur.

-Prone to bacterial and fungal infections.-Protective isolation required during this period.-Require multiple red cell and platelet

transfusions for the thrombocytopenia.-Engraftment considered successful when

peripheral ANC > 500/mm3 on three successive days.

Risk of GVHD after transplant -> irradiation prior to transplant to inactivate donor lymphocytes

GRAFT VERSUS HOST DISEASE

Occurs in allogeneic stem cell transplant. Acute / chronic . Acute : Occurs within the first 3 months after

transplantClassically affects only skin,gut and liver(skin lesions,diarrhoea,jaundice)Accompanied by fever

Chronic :Develops later than 100 days after the

transplant.De novo / follows acute GVHD .Limited/extensive .Resembles scleroderma( skin rash,sicca

complex,sclerosing bronchiolitis,hepatic dysfunction ).

Mortality of 20-40% .Mx – immunosuppressive agents.

Thank You!