Rare hematological disease - bone marrow failure
Aplastic anemia
Aplastic anemia, also known as medullary aplasia, is a rare and potentially serious disease characterized by the destruction or disappearance of hematopoietic stem cells in the bone marrow, leading to the latter's inability to produce sufficient quantities of the three blood cell lineages: red blood cells, white blood cells and platelets. This triple insufficiency, known as pancytopenia, exposes the patient to progressive anemia, a major infectious risk due to neutropenia, and potentially severe bleeding due to thrombocytopenia. Aplastic anemia affects around 2 to 3 people per million inhabitants per year, with a bimodal age distribution (peak in young adults aged 15 to 25, second peak after 60). Without treatment, severe forms are rapidly fatal, but the therapeutic advances made since the 1970s with bone marrow transplants and immunosuppressive treatments have radically transformed the prognosis of this disease.
What causes aplastic anemia?
In the vast majority of cases, aplastic anemia is acquired and autoimmune in origin: aberrantly activated T lymphocytes recognize and destroy hematopoietic stem cells as if they were foreign to the body. Identifiable causes account for around 20-30 % of cases, the remainder being classified as idiopathic.
| Category | Examples and mechanisms |
|---|---|
| Idiopathic (70 % of cases) | No cause identified despite exhaustive workup. Underlying autoimmune mechanism presumed in almost all cases: destruction of stem cells by CD8+ cytotoxic T lymphocytes producing pro-apoptotic cytokines (interferon-gamma, TNF-alpha). |
| Drugs and toxic substances | Certain drugs can trigger bone marrow aplasia by direct immunological or toxic mechanisms: chloramphenicol (the antibiotic most often incriminated historically), phenylbutazone, gold salts, D-penicillamine, carbamazepine, sulfonamides, certain anti-thyroid drugs (carbimazole), NSAIDs. Benzene and petroleum derivatives (occupational or chronic exposure). Anti-cancer chemotherapies cause a predictable and generally reversible dose-dependent aplasia, distinct from idiopathic aplastic anemia. |
| Viral infections | Hepatitis viruses (aplastic hepatitis: aplasia occurring 2 to 3 months after seronegative hepatitis, often in young men, post-infectious autoimmune mechanism). Epstein-Barr virus (EBV). Cytomegalovirus (CMV). Parvovirus B19 (pure erythroblastopenia rather than complete pancytopenia). HIV (aplasia due to direct progenitor infection or autoimmune mechanism). |
| Ionizing radiation | Exposure to high doses of radiation (nuclear accident, total body radiation therapy) causing dose-dependent direct destruction of hematopoietic stem cells. |
| Constitutional (genetic) causes | Fanconi anemia (autosomal recessive genetic disease with DNA repair defect, progressive bone marrow aplasia, congenital malformations and high risk of leukemia and solid tumors). Dyskeratosis congenita (mutation of telomerase genes with accelerated telomere shortening). Shwachman-Diamond syndrome. These constitutional forms account for around 15 to 20 % of childhood aplasias. |
| Associated autoimmune diseases | Systemic lupus erythematosus, eosinophilic fasciitis (classic association with bone marrow aplasia), autoimmune thyroiditis |
| Pregnancy | Rare gestational bone marrow aplasia, probably related to immunological mechanisms specific to pregnancy. May regress after delivery or require specific treatment. |
What are the symptoms?
The clinical manifestations of aplastic anemia are a direct consequence of the pancytopenia and its degree of severity. Onset may be gradual over several weeks, or abrupt, particularly in very severe forms.
| Deficient lineage | Clinical consequences | Signs and symptoms |
|---|---|---|
| Red blood cells (anemia) | Deficient oxygen transport to tissues | Intense, progressive fatigue, mucocutaneous pallor (conjunctivae, palms), dyspnea initially on exertion, then at rest in severe forms, palpitations, tachycardia, headaches, dizziness, intolerance to exertion. Anemia is normocytic normochromic, aregenerative (low reticulocytes). |
| White blood cells (neutropenia) | Deficiency of anti-infectious innate immunity | Recurrent or severe bacterial infections (pneumonia, septicemia, skin infections), invasive fungal infections (Aspergillus, Candida) in deep and prolonged neutropenia, fever with no apparent focus (medical emergency in severe neutropenia). Infectious risk is the main factor in short-term mortality |
| Platelets (thrombocytopenia) | Primary hemostasis deficiency | Mucocutaneous hemorrhagic syndrome: petechiae (red spots under the skin), ecchymotic purpura, gum bleeding, epistaxis (nosebleeds), menorrhagia in women. In very deep thrombocytopenia: risk of serious visceral haemorrhage, notably digestive haemorrhage or intracranial haemorrhage. |
Recognizing emergencies
In case of known or suspected aplastic anemia, seek immediate emergency care for: fever over 38.5°C (febrile neutropenia: infectious emergency requiring broad-spectrum antibiotic therapy within the hour), significant active bleeding (digestive hemorrhage, uncontrollable epistaxis, suspected intracranial hemorrhage with sudden headache or neurological disorders), or severe dyspnea at rest. These situations are life-threatening in the short term.
How is the diagnosis made?
- Complete blood count (CBC) with reticulocytes: reveals pancytopenia with normocytic normochromic anemia (collapsed reticulocytes), neutropenia and thrombocytopenia. The severity of cytopenia determines disease classification and therapeutic urgency.
- Bone marrow biopsy (BOM): essential anatomopathological examination, usually taken from the posterior iliac crest under local anaesthetic. Shows hypocellular or acellular bone marrow (less than 25 % of normal hematopoietic cells), replaced by adipose tissue, without blastic infiltration or fibrosis, confirming the diagnosis of bone marrow aplasia.
- Myelogram (bone marrow aspiration): completes the biopsy by enabling cytological analysis of the rare cells present and exclusion of myelodysplasia or leukemia.
- Marrow karyotype and molecular biology: search for chromosomal abnormalities (monosomy 7, 5q deletion) that may point to a myelodysplastic syndrome, and somatic mutations (DNMT3A, ASXL1, TP53) whose presence influences prognosis and response to treatment.
- Test for chromosomal fragility to alkylating agents (diepoxybutane or mitomycin C test): performed in all patients under 50 years of age to rule out Fanconi anemia before deciding on treatment, as this constitutional form contraindicates the alkylating agents used in standard transplant conditioning.
- Immunological and serological workup: viral serologies (EBV, CMV, parvovirus B19, HIV, hepatitis A, B, C), autoimmune workup (NAA, anti-DNA, complement), HLA typing of patient and siblings to identify a compatible donor for allogeneic transplantation
- Flow cytometry on peripheral blood: search for an HPN clone (paroxysmal nocturnal hemoglobinuria) due to a deficiency in GPI-anchored proteins (CD55, CD59). A small HPN clone is detected in 50 to 70 % of acquired aplasias, and is a marker of an autoimmune mechanism favoring a response to immunosuppressants.
Severity classification
| Shape | Hematological criteria | Therapeutic emergency |
|---|---|---|
| Not severe | Cytopenia not meeting severity criteria. Confirmed hypocellular marrow | Close monitoring, transfusions if necessary. Specific treatment if aggravation or transfusion dependence |
| Severe (SAA) | At least two of three criteria: neutrophils <0.5 × 10⁹/L, platelets <20 × 10⁹/L, reticulocytes <20 × 10⁹/L. Marrow cellularity <25 % | Urgent specific treatment (transplant or immunosuppression) as soon as possible. Protective isolation, antibiotic prophylaxis, transfusion support |
| Very severe (vSAA) | Severity criteria with neutrophils <0.2 × 10⁹/L | Absolute hematological emergency. Maximum infectious risk. Emergency transplant if donor available, otherwise intensive immunosuppression started immediately. |
What treatments are available?
| Treatment | Indications and mechanism | Comments and results |
|---|---|---|
| Allogeneic hematopoietic stem cell transplant (bone marrow transplant) | Reference curative treatment for patients under 40 (limit extended to 50-60 depending on center) with an intrafamilial HLA-identical donor (compatible brother or sister). Permanently replaces failing bone marrow with healthy donor marrow after immunosuppressive and myeloablative conditioning. Overall survival rate at 5 years greater than 90 % in young patients with geno-identical family donor | Main risk: acute and chronic graft-versus-host disease (GvHD), infections during the post-transplant aplasia period. Compatible unrelated donor transplant (international donor bank) possible if no family donor, with inferior results but constantly improving. Contraindicated in unconditioned Fanconi anemia. |
| Intensive immunosuppression (antilymphocytic serum + cyclosporine) | Reference treatment for patients without a compatible donor or over 40-50 years of age. Equine antilymphocyte serum (EAS) destroys the autoreactive T lymphocytes responsible for stem cell destruction. Ciclosporin inhibits T lymphocyte activation and is maintained over the long term to prevent relapses. | Response rate of 60 to 70 %. Response time 3 to 6 months. Risk of relapse when ciclosporin is reduced (20-30 %). Risk of late clonal evolution towards myelodysplastic syndrome, acute myeloid leukemia or paroxysmal nocturnal hemoglobinuria (long-term monitoring essential). |
| Thrombopoietin receptor agonists (eltrombopag) | Eltrombopag (Revolade) is an oral TPO receptor agonist that stimulates the proliferation of residual hematopoietic stem cells. Its combination with antilymphocyte serum and cyclosporine has significantly improved complete response rates in recent studies (complete response of 40 % versus 10 % with immunosuppression alone at 6 months). | represents a major therapeutic advance in the last decade. Now included as first-line therapy in combination with conventional immunosuppression in most international guidelines for patients without a family-identical donor. |
| Supportive treatment (transfusion support) | Transfusions of packed red blood cells to correct symptomatic anemia (hemoglobin target adapted to clinical tolerance, usually 80-90 g/L). Preventive platelet transfusions if platelets below 10 × 10⁹/L or in case of active bleeding. | Minimize pre-transplant transfusions to reduce anti-HLA alloimmunization, which increases the risk of graft rejection. Irradiation and leucodepletion of blood products recommended. Monitoring of martial overload (ferritin) in case of repeated transfusions, with iron chelation if necessary. |
| Hematopoietic growth factors | G-CSF (filgrastim) to stimulate neutrophil production in severe neutropenia with active infection. Erythropoietin in selected cases. Not a cure for aplasia, but may help to get through a critical period. | Limited efficacy in severe aplasia with very few residual stem cells. Mainly used as a complement to curative treatments |
| Infection prevention and treatment | Antibiotic prophylaxis with fluoroquinolones, prophylactic antifungals (posaconazole, voriconazole) and antivirals (aciclovir to prevent herpetic reactivation) in case of prolonged severe neutropenia. Broad-spectrum antibiotics to be started within the hour in case of fever (febrile neutropenia). | Protective isolation measures (laminar flow chamber) during phases of very deep neutropenia. Wear a surgical mask outside the room. Avoid microbiologically risky foods (raw vegetables, soft cheeses, cold meats). |
ℹ️
Aplastic anemia should not be confused with other causes of pancytopenia, which may have a similar clinical appearance but require radically different treatments: acute leukemia (presence of blasts on CBC and bone marrow aspiration), myelodysplastic syndrome (specific morphological and chromosomal abnormalities), lymphoma with bone marrow invasion, or bone marrow metastases of solid tumors. An osteo-medullary biopsy is essential for differential diagnosis.
What is the long-term follow-up?
Even after a complete response to treatment, patients with acquired aplastic anemia require regular long-term hematological follow-up. The main long-term concern is the risk of late clonal evolution, estimated at 10 to 20 % at 10 years, towards a myelodysplastic syndrome, acute myeloid leukemia or expansion of an HPN clone. This risk is linked to the genomic instability of stem cells that have survived autoimmune aggression and prolonged immunosuppressive therapy. Monitoring includes regular blood counts (every 3 to 6 months), annual flow cytometry for the HPN clone, and bone marrow karyotyping in the event of hematological abnormalities. Patients treated with allogeneic transplants benefit from specific post-transplant monitoring, including chronic GvHD, late infectious complications and conditioning side-effects.
Consult at Clinique Omicron
If you present with unexplained intense fatigue, repeated infections, a mucocutaneous hemorrhagic syndrome (petechiae, purpura, bleeding gums), or if a routine CBC reveals unexplained cytopenia, Clinique Omicron's physicians at its Quebec locations can initiate the first-line diagnostic workup and rapidly refer you to a hematologist for specialized management. Unexplained pancytopenia always requires prompt medical evaluation.
The content of this page is provided for informational purposes only and is not intended to replace the advice of a qualified healthcare professional. Consult a physician for any symptoms, questions or decisions you may have regarding your health.
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