Differential Diagnosis for Low Electrolyte and White Blood Cell Count with Fever

Single Most Likely Diagnosis

• Viral infection: A low white blood cell count (leukopenia) with low sodium (hyponatremia) and chloride levels, accompanied by fever, could be indicative of a viral infection. Viral infections can suppress bone marrow activity, leading to leukopenia, and can also cause electrolyte imbalances due to various mechanisms including excessive loss or hormonal changes.

Other Likely Diagnoses

• Bacterial infection with sepsis: Although the white blood cell count is low, which might not typically suggest bacterial infection, some bacterial infections, especially in their early stages or in immunocompromised patients, can present with leukopenia. Sepsis can also lead to electrolyte imbalances.
• Adrenal insufficiency: This condition can cause hyponatremia and hypochloremia due to the lack of aldosterone, which regulates electrolyte balance. Fever can be a non-specific symptom. Adrenal insufficiency can also lead to a relative leukopenia.
• Hypothyroidism: Though less common, severe hypothyroidism can lead to hyponatremia and can also affect the immune system, potentially leading to leukopenia and increased susceptibility to infections.

Do Not Miss Diagnoses

• Meningitis: Although the presentation might not be classic, meningitis can cause fever, electrolyte imbalances (due to syndrome of inappropriate antidiuretic hormone secretion, SIADH, or cerebral salt wasting), and leukopenia in some cases, especially if the patient is immunocompromised or the infection is caused by certain pathogens.
• Sepsis with a specific focus: Sepsis due to a specific infection (e.g., urinary tract infection, pneumonia) that could lead to severe electrolyte imbalances and leukopenia. Early recognition and treatment of sepsis are crucial.
• HIV/AIDS: Acquired immunodeficiency syndrome can present with a wide range of symptoms including fever, leukopenia, and various electrolyte imbalances due to opportunistic infections or the disease process itself.

Rare Diagnoses

• Lymphoma or leukemia: Certain types of lymphoma or leukemia can cause leukopenia, fever, and electrolyte disturbances, though these would typically be accompanied by other specific symptoms or findings on examination or imaging.
• Congenital adrenal hyperplasia crisis: Though rare in a 24-year-old, a late diagnosis or an undiagnosed case could present with electrolyte imbalances and fever during a crisis.
• Autoimmune disorders: Certain autoimmune disorders can affect the bone marrow, leading to leukopenia, and can also cause fever and electrolyte disturbances through various mechanisms.