Differential Diagnosis for a Baby with Fever and Hypotonia One Week After Delivery
- Single Most Likely Diagnosis
- d. GBS (Group B Streptococcus): This is the most likely diagnosis because Group B Streptococcus is a common cause of neonatal sepsis, particularly in the first week of life. GBS can cause a range of symptoms including fever, hypotonia, and respiratory distress. The fact that the baby is one week old and presenting with fever and hypotonia makes GBS a prime suspect.
- Other Likely Diagnoses
- a. Listeria: Listeria monocytogenes is another potential cause of neonatal sepsis, especially in the first week of life. It can cause similar symptoms to GBS, including fever and hypotonia. However, it is less common than GBS.
- c. Group A Streptococcus: While less common than GBS, Group A Streptococcus can also cause neonatal sepsis. It might present with similar symptoms, but it's not as frequently associated with neonatal infection as GBS.
- Do Not Miss Diagnoses
- b. Staphylococcus: Although Staphylococcus (including MRSA) can cause infections in newborns, it is less commonly associated with the presentation of fever and hypotonia in the first week of life compared to GBS or Listeria. However, due to its potential severity and resistance patterns, it should not be missed.
- Rare Diagnoses
- Other bacterial pathogens: Other bacteria like E. coli, Klebsiella, or Pseudomonas can cause neonatal sepsis but are less common causes of fever and hypotonia in the first week of life compared to the aforementioned pathogens.
- Viral infections: Certain viral infections can also present with fever and hypotonia, but they are less likely to be the primary cause in the context of neonatal sepsis in the first week of life.
For USMLE Step 3 purposes, recognizing GBS as the single most likely diagnosis due to its prevalence and association with neonatal sepsis is crucial. However, it's also important to consider other pathogens and to not miss diagnoses that could have significant morbidity or mortality if not promptly treated.