Neonatal hemolytic jaundice: morphologic features of erythrocytes that will help you diagnose the underlying condition.

BACKGROUND Many cases of severe neonatal hyperbilirubinemia never have the underlying cause of the jaundice clearly identified. Thus they are said to have 'idiopathic' severe neonatal jaundice. However, finding the exact cause, if it is a genetic condition, can enable informed anticipatory guidance regarding future episodes of hemolysis, anemia, or bilirubin cholelithiasis. OBJECTIVE 'Next generation' gene sequencing can often reveal the mutations responsible for severe neonatal hyperbilirubinemia, but wisely using this new technology involves selective application, employing this testing only if inexpensive technology fails to reveal the diagnosis. METHODS In this review, we display and discuss five types of red blood cell morphological abnormalities that have helped us categorize cases of neonatal hemolytic jaundice. RESULTS As an aid to applying inexpensive technology, we review morphological abnormalities of erythrocytes that are easily identified on a blood film. When found, these abnormalities can be important clues to the underlying hemolytic condition giving rise to neonatal jaundice. CONCLUSIONS Applying these simple and inexpensive methods can assist neonatologists in caring for neonates who have hemolytic jaundice. We predict that by using these principals the term 'idiopathic' neonatal jaundice will become less common as the underlying causes are identified.