Hematologic, Oncologic, Endocrine, and Metabolic Disorders
Hematology and metabolism demand pattern recognition
Physiologic anemia nadir occurs at 6–12 weeks in term infants and earlier in preterm infants. Polycythemia can cause hypoglycemia and hyperbilirubinemia; partial exchange transfusion is reserved for symptomatic infants with very high hematocrit. Vitamin K deficiency bleeding is prevented by intramuscular vitamin K at birth. Hemolytic disease of the newborn causes jaundice and anemia; direct antiglobulin testing and phototherapy are key. Congenital hypothyroidism is detected by newborn screening; delayed treatment impairs neurodevelopment. Congenital adrenal hyperplasia can present with salt-wasting crisis and ambiguous genitalia. Inborn errors of metabolism may present as encephalopathy, acidosis, or hyperammonemia.
Traps: treating physiologic jaundice with exchange transfusion; missing CAH because electrolytes are initially normal; and forgetting that vitamin K deficiency bleeding can occur after the first week in exclusively breastfed infants without prophylaxis.
Worked example: a 3-day-old exclusively breastfed infant has bleeding from the umbilical stump and a prolonged prothrombin time. Vitamin K is given, and the infant is evaluated for other causes.
Rule of thumb: “Jaundice plus anemia suggests hemolysis; jaundice plus lethargy suggests encephalopathy risk.”