Clinical and neuropsychological characteristics of general paresis misdiagnosed as primary psychiatric disease

BACKGROUND Neurosyphilis is caused by the invasion of Treponema pallidum into the central nervous system. General paresis (GP) is a type of neurosyphilis. The main manifestation of general paresis is dementia; however, this is different from the other types of dementia, which can be cured by adequate doses of penicillin in the early stage. Neurosyphilis is the "great imitator" because it can mimic many types of medical disorders. In addition, the manifestations of neurosyphilis are not typical. Psychiatric disorders as a cause of general paresis have become more common due to the use of antibiotics. Patients with a psychiatric manifestation are often misdiagnosed. The purpose of this study was to explore the differences in the clinical and neuropsychological characteristics of general paresis between patients misdiagnosed as having a primary psychiatric disease and patients diagnosed correctly upon seeing a doctor. The results may assist clinicians in the early identification of neurosyphilis with a mental disorder. METHOD The demographic and clinical manifestations, laboratory tests, and neuroimaging and neuropsychological characteristics were analysed in 55 general paresis patients with psychiatric disorders, including 29 patients misdiagnosed as primary psychiatric disease and 26 patients diagnosed as having general paresis after being seen once by a doctor. RESULT All of the patients had positive assay results for cerebral spinal fluid (CSF) Treponema pallidum hemagglutination (TPHA). Only 43.3 % of misdiagnosed patients and 30.8 % of general paresis patients had positive results for the CSF rapid plasma reagin (RPR) test; 96.4 % patients had abnormal neuroimaging. Mood disturbances were the most common psychiatric disorder in the general paresis patients, especially agitation, between the two groups (patients with general paresis who were misdiagnosed as having primary psychiatric disease and patients who had never been misdiagnosed) (p = 0.011). CONCLUSION Our findings reinforce the importance of performing serologic testing for syphilis. This should be a part of the evaluation of patients with psychiatric disorders, especially patients with cognitive impairment. When the syphilis serology is positive, the patient should be examined thoroughly for neurosyphilis by lumbar puncture. Brain imaging could also aid the physician in discriminating these patients from those with a functional mental disorder.