Summary of "CCH Session 4 - Megaloblastic Anemia, 11th June'23 IAP Delhi, Certificate Course Hematology"

Summary of the Video

CCH Session 4 - Megaloblastic Anemia 11th June 2023, IAP Delhi, Certificate Course Hematology Speaker: Dr. Puja Diwan (Professor of Pediatrics, Pediatric Hematology Oncology, University College of Medical Sciences & Guru Tegh Bahadur Hospital)

Main Ideas, Concepts, and Lessons

1. Introduction to Megaloblastic Anemia (MA)

Megaloblastic anemia is characterized by the presence of megaloblasts in bone marrow and macrocytes in peripheral blood.

Diagnosis requires bone marrow aspiration to confirm megaloblasts; otherwise, the term “macrocytic anemia” is preferred.
The most common cause (>95%) is nutritional deficiency, primarily Vitamin B12 and folic acid deficiency.

2. Pathogenesis of Megaloblastic Anemia

Vitamin B12 (cobalamin) is converted into methylcobalamin and adenosylcobalamin, essential for DNA synthesis and myelin formation.
Deficiency impairs DNA synthesis, causing nuclear-cytoplasmic asynchrony in erythroid precursors, resulting in megaloblasts.
Accumulation of homocysteine and methylmalonic acid (MMA) occurs; these are functional markers of B12 deficiency.
Folate participates in DNA synthesis via conversion of methyl tetrahydrofolate to tetrahydrofolate.

3. Epidemiology

High prevalence of B12 deficiency in children, especially adolescents (up to 31%) and infants (23%).
Folate deficiency is also common in adolescents (~37%).
Infants are at risk if mothers are deficient, especially in exclusively breastfed infants.

4. Etiology of Macrocytic Anemia

Primary cause: nutritional deficiency (B12 and folate).
Other causes include chronic liver disease, myelodysplasia, hypothyroidism, which cause macrocytosis without megaloblasts.
B12 deficiency is more common in vegetarians/vegans due to animal-based dietary sources.
Folate is abundant in green leafy vegetables.

5. Causes of B12 and Folate Deficiency

B12 deficiency:
- Dietary deficiency
- Malabsorption (pernicious anemia, intrinsic factor deficiency, gastrectomy, ileal diseases like Crohn’s, celiac)
- Transport defects
- Inborn errors of metabolism
Folate deficiency:
- Poor intake
- Malabsorption (tropical sprue, gastrectomy)
- Drug-induced (phenytoin, methotrexate)
- Increased requirement (pregnancy, hemolytic anemia)

6. Clinical Features

Insidious onset with anemia symptoms: lethargy, fatigue, anorexia, glossitis (beefy red tongue), stomatitis, hyperpigmentation (especially knuckles).
Neurological features in B12 deficiency: developmental delay, infantile tremor syndrome, peripheral neuropathy, loss of position/vibration sense.
Neurological severity may not correlate with hematological severity.

7. Laboratory Diagnosis

CBC shows macrocytic anemia, sometimes pancytopenia.
Peripheral smear: macro-ovalocytes, hypersegmented neutrophils (>5 lobes), Howell-Jolly bodies, Cabot rings.
Reticulocyte count is low due to ineffective erythropoiesis.
Serum B12 and folate levels should be measured but have limitations.
Functional markers:
- Serum homocysteine (elevated in both B12 and folate deficiency)
- Methylmalonic acid (MMA) (more specific for B12 deficiency)
Bone marrow aspiration reserved for atypical or severe cases.

8. Interpretation of Lab Tests and Diagnostic Algorithm

Low B12 + normal folate = B12 deficiency.
Low folate + normal B12 = folate deficiency.
Both normal with reticulocytosis = consider hemolysis or blood loss.
Both normal with reticulocytopenia = consider myelodysplastic syndrome (MDS), aplastic anemia, hypothyroidism, liver disease.

9. Treatment

Subclinical deficiency: dietary counseling and supplementation to meet RDA.
Clinical deficiency: start Vitamin B12 before folic acid to avoid neurological worsening.
Treatment routes:
- Parenteral (IM, SC): preferred in neurological cases, severe anemia, malabsorption.
- Oral high-dose B12: effective and emerging as a preferred route for compliance.
- Sublingual and intranasal routes are emerging but not widely recommended yet.
Dose considerations:
- Parenteral doses are lower due to better bioavailability.
- Oral doses are higher due to limited absorption.
Duration:
- Hematological manifestations treated for at least 3 months.
- Neurological manifestations treated for at least 6 months or lifelong in malabsorption/pernicious anemia.
Folic acid dose: typically 1.25 mg daily for up to 4 months; always exclude B12 deficiency before starting folic acid alone.
Monitor clinical response, CBC indices, and reticulocyte count.

10. Special Conditions

Infantile Tremor Syndrome: treat infant and mother simultaneously; symptomatic treatment for tremors may include propranolol, phenobarbitone, carbamazepine.
Pernicious Anemia: autoimmune, adolescent onset, associated with other autoimmune endocrinopathies; requires lifelong parenteral B12.
Neurological worsening can occur initially on B12 therapy; manage symptomatically without stopping treatment.
Side effects: rare allergic reactions, hypokalemia in severely anemic patients; test dose recommended for parenteral therapy.

11. Key Takeaways

Nutritional deficiency of B12 and folate is the leading cause of megaloblastic anemia in children.
Diagnosis is clinical supported by lab tests; no single test is definitive.
Early diagnosis and treatment prevent irreversible neurological damage.
Oral B12 is a promising alternative to injections in compliant patients.
Folic acid should never be given alone if B12 deficiency is suspected.
Follow-up is clinical and hematological rather than relying solely on serum B12 levels.

Detailed Methodology / Instructions for Clinicians

Diagnosis

Suspect megaloblastic anemia in macrocytic anemia with clinical features.
Confirm macrocytosis by MCV (>90 fL in children >10 years; use age-adjusted formula for younger children).
Examine peripheral smear for macro-ovalocytes and hypersegmented neutrophils.
Measure serum B12 and folate levels fasting.
Use homocysteine and MMA assays if diagnosis is unclear.
Bone marrow aspiration only if atypical features or poor response to treatment.

Treatment Protocol

Start parenteral B12 if neurological signs, severe anemia, or malabsorption.
Example parenteral dose: 25-100 mcg daily initially, then maintenance monthly.
Oral B12 dose: 500-1000 mcg daily for 3 months, then taper.
Start folic acid only after 1-2 weeks of B12 therapy.
In dimorphic anemia, add iron supplementation.
Monitor clinical and hematological response: reticulocytes rise in 48-72 hours, hemoglobin normalizes by 6-8 weeks.
Treat mother and infant together in infantile tremor syndrome.

Precautions

Do not give folic acid alone if B12 deficiency is suspected.
Monitor for allergic reactions during parenteral therapy.
Watch for neurological worsening after starting B12.
Assess compliance and investigate other causes if no response.

Speakers / Sources Featured

Dr. Puja Diwan – Professor of Pediatrics, Pediatric Hematology Oncology, University College of Medical Sciences and Guru Tegh Bahadur Hospital; main presenter.
Dr. Ajay – Moderator and faculty member, involved in session facilitation.
Dr. Jagdish Chandra – Director, IIT Delhi; provided comments and insights post-presentation.
Dr. Anurag – Faculty member, participated in discussion.
Other unnamed faculty and participants contributed during Q&A.

This summary captures the core educational content, clinical approach, and practical management guidelines for megaloblastic anemia in pediatric patients as presented in the session.