Severe Tick-Borne Encephalitis Diagnosis in an Immunocompromised Patient

Introduction Case presents diagnostic challenges of an immunocompromised patient with tick-borne encephalitis leading to rapid patient's health decline and significant intervention needed. Case Presentation A 39-year-old man was evaluated for impaired consciousness with potential causes including viral or autoimmune encephalitis, vasculitis, and progressive multifocal leukoencephalopathy (PML) due to systemic lupus erythematosus (SLE) treatment. He initially presented to the emergency department with fever, nausea, and headache but no focal or meningeal symptoms. Blood tests revealed leukopenia, thrombocytopenia, and mild CRP elevation. A recent tick bite raised suspicion of tick-borne encephalitis (TBE), though initial antibody tests were negative. He was discharged for outpatient care. Two weeks later, he returned with recurrent fever; lumbar puncture showed mild protein elevation. Extensive tests for HSV, JCV or antibodies for TBE (taken for the second time), were inconclusive. His condition deteriorated with respiratory insufficiency and altered consciousness (Glasgow Coma Scale 3). Imaging showed sinus infection and possible odontogenic infection that was later resolved, although the condition continued to worsen. A percutaneous tracheostomy was performed, and with no indications for ICU treatment, patient was transferred to Neurology. Later TBE was confirmed by positive IgM antibodies in Neurology only after the third time of testing and he was then transferred to Infectious Diseases. Discussion SLE patient with general infection-like symptoms rapidly declined neurologically without a conclusive diagnosis. Research reveals these issues in immunocompromised patients: lack of usual TBE symptoms, no antibody trigger response, unusual pathogens, drug toxicity. Are current guidelines for testing and diagnosing tick-borne encephalitis sufficient for immunocompromised patients? Conclusions Tick-borne encephalitis in an immunocompromised patient is a clinical and diagnostic difficulty because of lack of typical symptoms, low immune trigger, misleading virulence of unusual pathogens and extended convalescence.