Differential Diagnosis for Low-Grade Fever, Body Aches, Negative Tick Test, and Elevated Creatinine
- Single Most Likely Diagnosis
- Viral syndrome (e.g., influenza, COVID-19): This is a common cause of low-grade fever and body aches, and the negative tick test helps to rule out tick-borne illnesses. Elevated creatinine could be due to dehydration or a viral effect on the kidneys.
- Other Likely Diagnoses
- Bacterial infection (e.g., pneumonia, urinary tract infection): Although the tick test is negative, other bacterial infections could still be present, causing fever, body aches, and elevated creatinine due to sepsis or direct kidney involvement.
- Medication-induced nephrotoxicity: Certain medications can cause kidney damage, leading to elevated creatinine, and may also cause systemic symptoms like fever and body aches.
- Do Not Miss Diagnoses
- Sepsis: Although less likely given the low-grade fever, sepsis is a life-threatening condition that requires immediate attention. It can cause elevated creatinine due to kidney involvement and body aches due to the systemic inflammatory response.
- Kidney stones or obstruction: These conditions can cause severe pain (which may be perceived as body aches), fever, and elevated creatinine due to kidney damage or obstruction.
- Endocarditis: This is an infection of the heart valves and can present with low-grade fever, body aches, and elevated creatinine due to embolic events affecting the kidneys.
- Rare Diagnoses
- Vasculitis (e.g., ANCA-associated vasculitis): This is a group of diseases that cause inflammation of the blood vessels and can affect various organs, including the kidneys, leading to elevated creatinine and systemic symptoms.
- Connective tissue disease (e.g., lupus): These diseases can cause a wide range of symptoms, including fever, body aches, and kidney involvement leading to elevated creatinine.
- Hematologic malignancies (e.g., lymphoma): Although rare, these conditions can cause systemic symptoms like fever and body aches, and kidney involvement can lead to elevated creatinine.