syphilis is a type of sexually transmitted disease where the patient is infected by the spirochetal bacterium treponema pallidum.1 in last several decades , the occurrence of syphilis has declined ; however , a trend of syphilis resurgence in the 21st century has been documented.2 the world health organization reported that 36 million individuals were probably infected with syphilis in 2008.3 a previous study has estimated that a third of untreated syphilis patients will develop neurosyphilis ( the tertiary stage of syphilis ) , and that the central nervous system would be affected.4 however , the ability to diagnose neurosyphilis in the clinic is challenging , because the condition can imitate many neuropsychiatric diseases . the present study discusses a case of neurosyphilis in a young girl who was misdiagnosed as having viral encephalitis . a 15-year - old girl was admitted to our department in january 2012 because she was becoming increasingly more nervous and had been talking less since october 2011 . the patient s mother complained that the young girl did not communicate with others ; the patient showed restlessness , and she presented with tremors throughout her body . the patient had a temperature for several days in october 2011 , but she had a normal chest x - ray and abdominal ultrasonography . at the time , she was diagnosed as having viral encephalitis at the local hospital , and she was subsequently treated for a short time ( the details of the treatment are unknown ) . she was then transferred to the local mental hospital , where a magnetic resonance image ( mri ) of the head was taken ( the scan showed mild brain atrophy ) , and she was subsequently prescribed sulpiride ( maximum dose 1.2 g / day ) and benzhexol ( maximum dose 8 mg / day ) . however , it was found that the patient s condition did not improve , and her tremors became increasingly more severe . , we found that the patient had visual hallucinations , persecutory delusions , flattening of affect , poorness of thought , and four - limb rigidity . we consulted a neurologist because of the patient s tremors and four - limb rigidity ; we also stopped all antipsychotic treatments . the neurologist suggested we should arrange mri scanning and lumbar puncture again , and the venereal disease research laboratory ( vdrl ) serum test under the suspicion of some rare diseases , such as human immunodeficiency virus infection . the vdrl serum test yielded positive results with respect to the t. pallidum antibody ( tpa ) ; we then found a titer of 1:4 with respect to the toluidine red unheated serum test ( trust ) , and we obtained positive results on the t. pallidum particle - agglutination test . a lumbar puncture was then performed under the suspicion that the patient had neurosyphilis , and the results showed that the cerebral spinal fluid vdrl was 1:2 ( reactive ) , the karyocyte level was 1010/l  , the igg synthetic rate was 153.275 mg / day  , the igg level was 0.3790 g / l  , the albumin level was 0.6870 g / l  , and the microalbumin level was 1.26 g / l . after consulting an infection specialist , we prescribed penicillin ( 3 mu ) every 4 hours for 14 days , and a penicillin benzathine ( 2.4 million iu ) intramuscular injection once a week for 3 weeks . after 3 months , the patient s tremors and limb rigidity were relieved , and her hallucinations and delusions disappeared . her total score on the positive and negative syndrome scale decreased from 115 ( baseline ) to 39 ( 3 months ) , and her unified parkinson s disease rating scale ( updrs ) score decreased from 129 ( baseline ) to 32 ( 3 months ) . the patient became relaxed ; she no longer nervously paced around , and she sometimes spoke with her family members . symptoms of hallucinations , delusions , flattening of affect , poorness of thought , and other psychotic symptoms can be found in many diseases . this particular case provided an important perspective so that clinicians can properly diagnose a disease that presents with psychotic symptoms as the first sign of disease onset . in this case , we accidentally discovered this patient s neurosyphilis via a vdrl serum test . this indicated that we should pay attention to complicated psychotic symptoms and treatment - resistant psychosis . some patients might conceal their sexual history , as had occurred with this young girl , who had been raped 2 years prior to symptom onset . some case reports have described psychosis in neurosyphilis.5,6 in the present case , the patient s psychotic symptoms disappeared following antibiotic treatment ; however , whether an antipsychotic should be used , and what kinds of antipsychotics should be used , are unknown . at the same time , we wanted to exclude the extrapyramidal side effects associated with antipsychotics , which might have caused the patient s tremors and rigidity . to our knowledge , no consensus or guidelines as to how to treat psychotic symptoms associated with neurosyphilis have been established to date.7 studies in this area are also limited . therefore , it is crucial that further research be conducted in this field in the future . parkinsonism , which includes such symptoms as tremors and rigidity , has also been reported in another study on neurosyphilis.8 one possible reason for the development of parkinsonism is that the basal ganglia is impaired in these patients . brain atrophy , as shown on mri , also provides clues regarding impaired cerebral function . however , there is a lack of consistent pathological radiographic findings that can be considered characteristic of neurosyphilis.9 as a psychiatrist , it is important to keep organic psychosis in mind when facing complicated or treatment - resistant psychotic symptoms , such as those associated with neurosyphilis . on the other hand , routine syphilis screening is necessary in the psychiatry department . given that a patient s sexual history is deemed highly confidential in some countries , including in the people s republic of china , it is very difficult to obtain a patient s complete sexual history . as such