Differential Diagnosis for Negative Symptoms without Full Schizophrenia Criteria

• Single most likely diagnosis:
  • Schizoid Personality Disorder: This diagnosis is likely because the patient exhibits negative symptoms such as social isolation and lack of interest in social relationships, which are characteristic of schizoid personality disorder. However, it's crucial to differentiate this from schizophrenia spectrum disorders.
• Other Likely diagnoses:
  • Schizophrenia Spectrum Disorder (e.g., Schizotypal Personality Disorder): These disorders share some symptoms with schizophrenia but do not meet the full criteria. They can present with negative symptoms and are part of the schizophrenia spectrum.
  • Depressive Disorder with Psychotic Features: Sometimes, depressive disorders can present with psychotic features that might mimic schizophrenia, including negative symptoms. It's essential to assess for a depressive episode.
  • Brief Psychotic Disorder: Although this condition is characterized by a short duration of psychotic symptoms, some patients might exhibit negative symptoms during or after the psychotic episode.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed):
  • Neurosyphilis: This condition can present with psychiatric symptoms, including negative symptoms resembling schizophrenia. Given its severe consequences if untreated, it's crucial to rule out neurosyphilis.
  • Temporal Lobe Epilepsy: Some forms of epilepsy, particularly those involving the temporal lobe, can cause psychiatric symptoms that might be confused with schizophrenia, including negative symptoms.
  • Vitamin B12 Deficiency: Severe vitamin B12 deficiency can lead to neurological and psychiatric symptoms, including those that resemble negative symptoms of schizophrenia.
• Rare diagnoses:
  • Ekbom Syndrome (Delusional Parasitosis): Although rare, this condition involves delusional beliefs of being infested with parasites and can sometimes present with negative symptoms.
  • Capgras Syndrome: A rare delusional disorder where the patient believes a friend, spouse, parent, or other close family member has been replaced by an identical impostor. It might occasionally be associated with negative symptoms.