Can a tick-borne illness cause hyponatremia?

From the Guidelines

Yes, tick-borne illnesses can cause hyponatremia (low sodium levels in the blood). Several tick-borne diseases, particularly Rocky Mountain spotted fever, ehrlichiosis, and anaplasmosis, have been associated with hyponatremia as a clinical manifestation, as noted in the management of severely ill patients with tickborne rickettsial disease, which includes assessment of fluid and electrolyte balance 1. This occurs through multiple mechanisms, including the syndrome of inappropriate antidiuretic hormone secretion (SIADH), where inflammation and cytokine release during infection disrupt normal water regulation. Additionally, some patients may develop cerebral salt wasting or experience direct kidney injury from the infection. The hyponatremia typically resolves with appropriate treatment of the underlying tick-borne illness, which usually involves doxycycline (100mg twice daily for 7-14 days, depending on the specific infection), as recommended for the treatment of tickborne rickettsial diseases 1. Patients with severe hyponatremia (sodium <125 mEq/L) may require additional management with fluid restriction or hypertonic saline depending on symptoms and severity. Clinicians should consider tick-borne illness in patients presenting with unexplained hyponatremia, especially when accompanied by fever, headache, rash, or recent tick exposure in endemic areas.

Some key points to consider in the management of tick-borne illnesses include:

• Early empiric treatment with doxycycline is crucial to prevent severe disease and death 1
• Patients with evidence of organ dysfunction, severe thrombocytopenia, mental status changes, or the need for supportive therapy should be hospitalized 1
• The recommended dose of doxycycline for the treatment of tickborne rickettsial diseases is 100 mg twice daily (orally or intravenously) for adults and 2.2 mg/kg body weight twice daily (orally or intravenously) for children weighing <100 lbs (45 kg) 1
• Delay in treatment can lead to severe disease and fatal outcome of TBRD 1

It is essential to note that while the provided evidence does not directly address the question of hyponatremia in tick-borne illnesses, the management of these diseases involves careful monitoring of fluid and electrolyte balance, which can help identify and manage hyponatremia. Therefore, clinicians should be aware of the potential for hyponatremia in patients with tick-borne illnesses and manage it accordingly.

From the Research

Tick-Borne Illnesses and Hyponatremia

• Tick-borne illnesses can cause hyponatremia, as evidenced by several case reports and studies 2, 3, 4, 5, 6.
• Hyponatremia is a common disorder in the course of tick-borne encephalitis (TBE), although it is not significantly more frequent than in other hospitalized patients 5.
• The most common cause of hyponatremia in TBE patients is dehydration, and fluid supplementation should be the treatment of choice 5, 6.
• However, the syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a less common cause of hyponatremia in TBE patients, but it should be taken into consideration as the treatment differs significantly 4, 5, 6.

Specific Tick-Borne Illnesses and Hyponatremia

• Lyme disease, caused by the bacterium Borrelia burgdorferi, can cause hyponatremia, as well as SIADH-like syndrome, enteroparesis, and urinary retention 2.
• Ehrlichiosis, a tick-borne infection, can also cause hyponatremia, as well as acute encephalopathy and hemophagocytic lymphohistiocytosis 3.
• Neuroborreliosis, a manifestation of Lyme disease, can cause SIADH and hyponatremia, especially in patients with atypical presentations 4.

Risk Factors and Frequency

• Patients with TBE are more susceptible to hyponatremia than younger patients, with a correlation between sodium concentration and patient age 5.
• The frequency of hyponatremia and SIADH is higher in TBE patients than in patients with viral meningitis of other origin, especially in young patients (<35 years) 6.
• Overall, 16.9% of patients with the severe form of TBE develop SIADH syndrome and require treatment based on fluid restriction and hypertonic saline infusion 6.