Treatment of rare forms of anemia

Article written and reviewed by Dr Luca Moretti

Rare anemias comprise a heterogeneous group of disorders, often of genetic or acquired etiology, characterized by low prevalence and considerable diagnostic and therapeutic complexity. These conditions include congenital anemias due to red blood cell membrane defects, less common hemoglobinopathies, red blood cell enzyme deficiencies, sideroblastic anemias, pure red cell aplasias, anemias associated with rare autoimmune disorders and numerous other hematologic syndromes with an anemic phenotype that does not fall within common forms. Treatment is based on a personalized approach that considers pathogenesis, severity, comorbidities and the most recent pharmacologic and molecular advances.

General principles of treatment

Management of rare anemias requires an integrated assessment that includes confirmation of the specific diagnosis through advanced laboratory investigations and, increasingly, molecular diagnostics. The rarity of these conditions makes referral to multidisciplinary specialist centers necessary, where care can draw on hematologic, genetic and internal medicine expertise and, in some cases, pediatric expertise because onset often occurs at a young age. Treatment should aim not only to control symptoms, but also to prevent long term complications and improve quality of life.

The main goals are:

• Stabilize red blood cell function and limit transfusion requirements.
• Prevent or treat specific complications, including iron overload, aplastic crises and opportunistic infections.
• Integrate symptomatic therapies with etiologic and, where possible, curative approaches.

In most cases, treatment must be adjusted according to clinical course, response to therapy and patient characteristics.

Specific therapies for the main rare forms of anemia

Within rare anemias, each subtype has specific therapeutic features. The most current strategies for the principal nosologic groups are discussed below.

Anemias due to red blood cell enzyme deficiencies

The best known forms include glucose 6 phosphate dehydrogenase (G6PD) deficiency, pyruvate kinase deficiency and other rare deficiencies, such as hexokinase and pyrimidine 5' nucleotidase deficiency. In G6PD deficiency the cornerstone of management includes avoidance of oxidative triggers, including medications and foods associated with risk, and prompt treatment of hemolytic crises. In other red blood cell enzymopathies, including pyruvate kinase deficiency, management must instead be adapted to the specific disorder and its severity. For pyruvate kinase deficiency in adults, mitapivat is available as an allosteric pyruvate kinase modulator authorized in the European Union for adult patients. Efficacy depends on genotype and clinical profile; in selected cases, splenectomy remains an option to be weighed against infectious and thrombotic risks. Mitapivat is also authorized in the European Union for adults with anemia associated with alpha or beta thalassemia, whether transfusion dependent or non transfusion dependent, according to the product information.

Anemias due to red blood cell membrane defects

This group includes hereditary spherocytosis, elliptocytosis, stomatocytosis and, rather rarely, acanthocytosis. In hereditary spherocytosis, splenectomy is a selective option, mainly reserved for moderate or severe forms with symptomatic anemia, clinically significant hemolysis or transfusion requirements, with the aim of reducing peripheral red blood cell destruction. Before splenectomy, vaccination against pneumococcus, meningococcus and Haemophilus influenzae and long term planning of infectious surveillance are essential. In some forms of elliptocytosis and stomatocytosis, splenectomy may be ineffective or even contraindicated, and treatment remains predominantly symptomatic.

Sideroblastic anemias

Sideroblastic anemias are a heterogeneous group of disorders characterized by mitochondrial iron accumulation in erythroid precursors with formation of ring sideroblasts; pathogenic mechanisms include defects in heme synthesis, iron sulfur cluster biogenesis, mitochondrial protein synthesis and acquired causes. The rarer inherited forms may benefit from pyridoxine (vitamin B6) in responsive variants, whereas acquired forms, such as those associated with myelodysplastic syndromes, require specific treatment of the underlying disease and careful management of iron overload. When clinically significant iron overload is present, iron chelation may be necessary and, in severe forms, treatment specific to the etiology and subtype may be required; interferon alfa is not a standard therapy for sideroblastic anemia.

Rare autoimmune anemias

Direct antiglobulin test negative autoimmune hemolytic anemias require more sensitive methods and exclusion of nonimmune causes; membrane defects are not autoimmune forms. Treatment depends on the phenotype: corticosteroids are generally first line for warm forms, whereas immunoglobulins, rituximab and other immunosuppressants have selected indications, integrated with strategies to prevent opportunistic infections and manage treatment related complications.

Fanconi anemia and other congenital bone marrow failure syndromes

Fanconi anemia, a paradigm of congenital bone marrow failure syndromes, is characterized by progressive pancytopenia, somatic abnormalities and a high risk of leukemic evolution. Treatment is based on allogeneic hematopoietic stem cell transplantation, which can correct bone marrow failure but not congenital abnormalities or cancer predisposition. Androgens may provide temporary hematologic benefit in selected cases; corticosteroids are not standard treatment for Fanconi anemia. Management requires close monitoring for infectious complications, associated malignancies and extrahematologic manifestations.

Anemias associated with rare genetic or syndromic disorders

A paradigmatic example is Diamond Blackfan anemia, most often associated with pathogenic variants in genes involved in ribosome biogenesis but with some nonribosomal causes, classically characterized by macrocytic anemia and reticulocytopenia with typically pediatric onset. In patients with Diamond Blackfan anemia who are candidates for steroid therapy, corticosteroids are introduced according to specialist protocols with a defined initial dose followed by reduction to the lowest effective dose; chronic exposure to high doses should be avoided because of toxicity. Some patients are resistant or develop significant adverse effects. In these cases, hematopoietic stem cell transplantation can correct the hematologic defect, but not all congenital manifestations or the predisposition to malignancy. Clinical studies are underway on new agents aimed at correcting the ribosomal synthesis defect or modulating the erythropoietic response.

Management, follow up and prognosis of rare anemias

Management of rare anemias poses distinctive organizational and clinical challenges that require multidisciplinary care and individualization of the treatment pathway. Low prevalence and considerable heterogeneity of presentation often make referral to regional or national centers of expertise necessary, where advanced diagnostic resources and teams experienced in hematology, genetics, infectious diseases, nephrology and internal medicine are available and, for pediatric patients, specialist expertise in pediatrics and clinical psychology can be provided.

A key aspect is ensuring a timely and accurate diagnosis, which often requires second or third level molecular tests, investigations of red blood cell function, including osmotic fragility, hemoglobin electrophoresis and specific enzyme assays, and in some cases genomic sequencing. Access to these investigations should be facilitated by defined diagnostic pathways that reduce the risk of delayed or incorrect diagnosis, which unfortunately remains frequent in rare disorders.

Follow up planning must be personalized according to the type of anemia, age, clinical severity and risk of complications. In chronic transfusion dependent forms, surveillance should include monitoring of iron overload with ferritin and liver or cardiac MRI, liver and cardiac function, and early identification of endocrine and metabolic complications. In rare autoimmune anemias, follow up should integrate assessment of the response to immunosuppression, detection of opportunistic infections, surveillance for adverse effects of long term therapy and the risk of evolution toward other cytopenias or lymphoproliferative syndromes.

In all rare forms, management of complications is a cornerstone. The main problems include:

• Iron overload in patients requiring chronic transfusions, which calls for careful chelation management and periodic surveillance of target organs.
• Infectious risk after splenectomy, which requires complete vaccination and sometimes prolonged antibiotic prophylaxis.
• Thrombotic complications, especially in some forms such as hereditary stomatocytosis or syndromes with endothelial dysfunction.
• Psychological and social support, particularly relevant in disorders with pediatric onset or a significant impact on quality of life.

Collaboration with transfusion medicine, endocrinology, cardiology and psychology services can contribute to better overall patient management.

The prognosis of rare anemias is extremely variable and depends on the specific disorder, severity of presentation, response to conventional treatments and timeliness of therapeutic intervention. In some forms, such as mild enzymatic anemias or well compensated spherocytosis, life expectancy may be similar to that of the general population provided related risks, including hemolytic crises, post splenectomy infections and gallstones, are managed correctly. By contrast, in congenital aplasias, bone marrow failure syndromes or anemias associated with complex genetic disorders, prognosis may be severely compromised, especially when curative treatment options are unavailable.

An increasingly important role is played by rare disease networks and patient associations, which facilitate access to specialist pathways, promote clinical research and support dialogue among patients, families and clinicians. Participation in international registries and collaborative studies makes it possible to accumulate valuable data on the natural history of rare diseases and improve the quality of care and follow up strategies.

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