Overview
Definition:
Microcytic anemia is characterized by red blood cells (RBCs) with a mean corpuscular volume (MCV) less than 70 fL in infants and less than 78 fL in older children, indicating smaller-than-normal RBCs
The most common causes in pediatrics are iron deficiency anemia (IDA) and thalassemia trait
Differentiating these is crucial for appropriate management and avoiding unnecessary interventions.
Epidemiology:
Iron deficiency anemia is the most common nutritional deficiency and the leading cause of anemia worldwide, particularly in infants and toddlers due to inadequate dietary intake or increased requirements
Thalassemia trait, a group of inherited disorders of hemoglobin synthesis, is prevalent in populations of Mediterranean, Middle Eastern, South Asian, and Southeast Asian descent.
Clinical Significance:
Accurate differentiation is vital as IDA is treatable with iron supplementation, whereas iron therapy in thalassemia trait can lead to iron overload and may not correct the anemia
Misdiagnosis can lead to ineffective treatment and potential harm
Understanding these differentials is a core competency for pediatricians preparing for DNB and NEET SS exams.
Clinical Presentation
Symptoms:
Asymptomatic in mild cases
Fatigue
Irritability
Poor feeding
Pallor
Delayed developmental milestones
In severe IDA: Pica (eating non-food substances like dirt or ice)
In thalassemia trait: Often asymptomatic, may have mild pallor.
Signs:
Pallor of mucous membranes and conjunctiva
Mild jaundice in severe IDA
Splenomegaly may be present in severe IDA or advanced thalassemia
Possible heart murmurs due to anemia
Growth retardation in chronic, severe cases.
Diagnostic Criteria:
Diagnosis is primarily based on laboratory findings
Red blood cell indices (low MCV, low MCH, normal or elevated RBC count in thalassemia trait vs
low RBC count in IDA) are key
Further testing is required for definitive diagnosis
No specific clinical diagnostic criteria, reliance on investigations.
Diagnostic Approach
History Taking:
Detailed dietary history (iron intake, exclusive breastfeeding beyond 6 months, consumption of milk)
Family history of anemia or blood disorders
Birth history (prematurity, birth weight)
History of blood loss (GI bleeding, menorrhagia in older girls)
Geographical origin/ethnicity (suggestive of thalassemia)..
Physical Examination:
General appearance: assessment for pallor, fatigue, developmental delay
Vital signs: tachycardia may be present
Cardiovascular system: murmurs
Abdomen: palpation for splenomegaly or hepatomegaly
Skin: pallor, petechiae (if other causes suspected).
Investigations:
Complete Blood Count (CBC): MCV, MCH, MCHC, RDW
Peripheral Blood Smear: Microcytosis, hypochromia, anisocytosis, poikilocytosis (target cells, basophilic stippling in thalassemia)
Iron Studies: Serum ferritin (low in IDA, normal/high in thalassemia), serum iron, TIBC, transferrin saturation
Hemoglobin Electrophoresis: Definitive for thalassemia trait (elevated HbA2 > 3.5%).
Differential Diagnosis:
Other causes of microcytic anemia include anemia of chronic disease, lead poisoning, sideroblastic anemia, and vitamin B6 deficiency
Thalassemia trait and IDA are the most common and crucial to distinguish
Lead poisoning: history of exposure, basophilic stippling
Anemia of chronic disease: typically less severe microcytosis, normal iron stores
Sideroblastic anemia: ring sideroblasts on bone marrow aspirate.
Management
Initial Management:
For suspected IDA: empirical trial of oral iron therapy (e.g., ferrous sulfate 3-6 mg/kg/day divided into 1-3 doses)
For suspected thalassemia trait: avoid iron therapy unless iron deficiency is confirmed
Further investigations to confirm diagnosis are paramount before initiating treatment.
Medical Management:
Iron Deficiency Anemia: Oral iron supplementation is the mainstay
Dosage: 3-6 mg/kg/day of elemental iron for IDA
Duration: typically for 3-6 months after normalization of hemoglobin
Parenteral iron (IV/IM) may be used in cases of malabsorption, intolerance, or severe anemia
Thalassemia Trait: No specific medical management for trait itself
focus on education and avoiding unnecessary iron
If concurrent IDA, iron therapy is indicated.
Surgical Management:
Not typically indicated for uncomplicated thalassemia trait or IDA
Splenectomy may be considered in very rare cases of severe thalassemia intermedia or major with hypersplenism, but this is outside the scope of trait management.
Supportive Care:
Dietary counseling for adequate iron-rich foods in IDA
Regular monitoring of hemoglobin and iron indices
Genetic counseling for families with thalassemia trait
Education regarding potential complications if IDA is severe or left untreated.
Complications
Early Complications:
In severe IDA: heart failure, developmental delay, neurological deficits
In thalassemia trait: iron overload from inappropriate iron supplementation
Increased susceptibility to infections in severe anemia.
Late Complications:
IDA: persistent developmental delays, reduced cognitive function
Thalassemia Trait: minimal complications if not over-treated with iron
risk of iron overload if diagnosis is missed and iron is administered
Carrier status implications for offspring.
Prevention Strategies:
Routine screening for anemia in infants and toddlers
Iron-fortified formula and cereals
Adequate maternal iron intake during pregnancy
Public health initiatives promoting iron-rich diets
Neonatal screening for hemoglobinopathies in high-prevalence areas.
Key Points
Exam Focus:
Key differentiating features: serum ferritin (low in IDA, normal/high in thalassemia), hemoglobin electrophoresis (HbA2 > 3.5% in thalassemia trait), RBC count (often normal/high in thalassemia trait vs
low in IDA)
Remember RDW is often high in IDA but normal/low in thalassemia trait
Treat IDA, educate about thalassemia trait.
Clinical Pearls:
Always consider thalassemia trait in infants of Asian or Mediterranean descent presenting with microcytosis
Never assume anemia is IDA without proper investigation, especially if symptoms or lab findings are atypical
A normal or high RBC count with microcytosis is a strong clue for thalassemia trait.
Common Mistakes:
Treating all microcytic anemias with iron without definitive diagnosis
this can lead to iron overload in thalassemia trait
Failing to perform hemoglobin electrophoresis when thalassemia is suspected
Overlooking other causes of microcytic anemia in atypical presentations.