Introduction: Catatonia is a neuropsychiatric syndrome with motor and behavioral symptoms. In addition to psychiatric illnesses, this syndrome can also be associated with general medical conditions. Few cases of catatonia associated with autoimmune disorders have been reported.
Case report: We report the case of a 56-year-old female patient diagnosed with Hashimoto's encephalitis, who presented firstly with mystical delusions and tachypsychia. Despite the proper treatment for psychosis, the symptoms worsened and she developed catatonia. Complementary investigations showed high titers of anti-thyroperoxidase antibodies. Hashimoto encephalitis was suspected and intravenous prednisolone was started. As there was an only partial improvement in psychiatric symptoms, plasmapheresis was chosen. The patient evolved with a drastic improvement in symptoms after the third session of plasmapheresis.
Conclusion: An organic etiology should always be considered in cases of catatonia, especially in those with no previous psychiatric history. Doctors should always think about measuring thyroid function when faced with a case of catatonia.