Differential Diagnosis
The patient presents with low lymphocytes, low eosinophils, elevated neutrophils, normal WBC, fever, mild tachycardia, recent UTI treatment, negative COVID-19 and flu tests, headache, and cough. Here's a categorized differential diagnosis:
- Single Most Likely Diagnosis
- Bacterial Infection: Given the recent treatment for UTI and the presence of fever, headache, and cough, a bacterial infection (possibly a different site than the urinary tract or a complication of the UTI) is a strong consideration. The elevated neutrophils support a bacterial etiology.
- Other Likely Diagnoses
- Viral Infection: Despite negative COVID-19 and flu tests, especially considering they were done early in the course of symptoms, a viral infection cannot be ruled out. Some viruses can cause secondary bacterial infections, which might explain the elevated neutrophils.
- Partial Treatment or Complicated UTI: Although the repeat urine test was normal, it's possible that the UTI was not fully eradicated or has complicated into a different form (e.g., pyelonephritis), which could explain the ongoing symptoms.
- Do Not Miss Diagnoses
- Sepsis: Any infection that leads to a systemic inflammatory response syndrome (SIRS) can progress to sepsis, a life-threatening condition. The presence of fever, tachycardia, and abnormal white blood cell count (despite being normal overall, the differential is concerning) necessitates consideration of sepsis.
- Endocarditis: Although less common, endocarditis can present with fever, headache, and cough, especially if there's an embolic phenomenon. The recent history of UTI and possible bacteremia increases the risk.
- Rare Diagnoses
- Lymphoma or Leukemia: These conditions can cause abnormalities in the white blood cell count, including low lymphocytes. However, they would be less likely given the acute presentation and the context of recent infection.
- Autoimmune Disorders: Certain autoimmune disorders can cause fever, headache, and abnormalities in blood cell counts. However, these would typically have other distinguishing features and a more chronic course.
Each of these diagnoses should be considered in the context of the patient's full clinical picture, including further history, physical examination, and diagnostic tests as necessary.