Differential Diagnosis for Tick-Borne Illness with Hyponatremia, Leucocytosis, and Neuropathy

• Single Most Likely Diagnosis
  • Lyme Disease: Caused by Borrelia burgdorferi, transmitted by the black-legged tick. It can present with a wide range of symptoms including neuropathy (neuroborreliosis), which can lead to neurological manifestations. Hyponatremia and leucocytosis can occur due to the systemic inflammatory response and possible central nervous system involvement. Lyme disease is one of the most common tick-borne illnesses in the United States and Europe, making it a likely diagnosis in endemic areas.
• Other Likely Diagnoses
  • Rocky Mountain Spotted Fever (RMSF): Caused by Rickettsia rickettsii, transmitted by the American dog tick, Rocky Mountain wood tick, and the brown dog tick. RMSF can cause severe illness with symptoms including fever, headache, and rash, and can lead to neurological manifestations and hyponatremia due to increased vascular permeability and systemic inflammation. Leucocytosis is also common.
  • Southern Tick-Associated Rash Illness (STARI): Also known as Masters disease, it presents similarly to Lyme disease with a rash but is caused by the lone star tick. While less is known about its ability to cause hyponatremia, leucocytosis, and neuropathy compared to Lyme, it remains a consideration in areas where the lone star tick is prevalent.
• Do Not Miss Diagnoses
  • Tick-Borne Relapsing Fever (TBRF): Caused by several Borrelia species transmitted by soft ticks. TBRF can lead to severe neurological manifestations, including neuropathy, and can cause hyponatremia and leucocytosis due to the relapsing nature of the fever and the body's response to the infection. Missing this diagnosis could lead to severe outcomes due to its potential for causing significant morbidity.
  • Ehrlichiosis: Caused by Ehrlichia species, transmitted by the lone star tick and the black-legged tick. Ehrlichiosis can present with fever, headache, and fatigue, and can lead to more severe manifestations including neurological symptoms and hyponatremia. It's crucial not to miss this diagnosis due to its potential severity, especially in immunocompromised patients.
• Rare Diagnoses
  • Babesiosis: Caused by Babesia species, transmitted by the black-legged tick. While primarily known for causing hemolytic anemia, babesiosis can lead to systemic symptoms and, in rare cases, neurological manifestations. Hyponatremia and leucocytosis can occur due to the systemic inflammatory response.
  • Powassan Virus Disease: A rare but potentially severe tick-borne illness that can cause encephalitis and meningitis, leading to neuropathy. Hyponatremia and leucocytosis can be present due to the central nervous system involvement and the body's inflammatory response. Its rarity makes it less likely but not to be missed due to its potential severity.