Hematologic and Immunologic Disorders
Core concepts
Understand physiologic anemia of infancy, anemia of prematurity, and the indications for transfusion. Know hemolytic disease of the newborn (Rh and ABO incompatibility), including the direct Coombs test, and the prevention of Rh sensitization with Rh immune globulin. Grasp neonatal thrombocytopenia and its causes, vitamin K deficiency bleeding and the rationale for prophylactic vitamin K, and the recognition of sepsis-related coagulopathy. Understand immune function in the newborn: passive maternal antibodies, the timing of immunoglobulin transfer, and the immunologic benefits of breast milk. Know the presentation of severe combined immunodeficiency and the rationale for avoiding live vaccines in immunocompromised infants.
Traps
Questions test that Rh immune globulin prevents sensitization but does not treat an already sensitized mother. Another trap: forgetting vitamin K prophylaxis prevents classic hemorrhagic disease of the newborn. Also beware confusing physiologic anemia (nadir around 8-12 weeks in term infants) with pathologic hemolysis.
Worked example
An Rh-negative mother delivers an Rh-positive infant and is unsensitized. Rule of thumb: give Rh immune globulin within 72 hours of delivery to prevent sensitization; confirm with a negative antibody screen.
Study focus
Separate preventive interventions from treatments and link each to the underlying mechanism.