ABSTRACT
Vitamin B12 is one of the essential vitamins affecting various systems of the body. Cases of neuropsychiatric disorders due to its deficiency are more common in elderly patients with a prevalence rate of 10-20%; however there have been few cases reported in children and adolescents as well. The most common psychiatric symptoms reported in the literature associated with vitamin B12 deficiency was depression, mania, psychotic symptoms, cognitive impairment, dementia,delirium, acute confusional states and obsessive compulsive disorder. Subacute combined degeneration (SCD) is a neurological complication of vitamin B12 deficiency, characterized by demyelination of the dorsal and lateral spinal cord. With an early diagnosis and treatment, further development of symptoms can be prevented, before psychosis; dementia and severe depression can develop. The treatment is simple and effective and often gives very good results in these symptoms. Here we have reported a case of vitamin B12 deficiency in 19 years old, male who presented with months history of paraparesis and 3 months history of psychosis. The patient was non vegetarian. Past medical history, was insignificant. Premorbid personality was unremarkable with no substance use/ exposure or infections. No stressors were present. He was diagnosed with sub acute combined degeneration with psychosis due to vitamin B12 deficiency. He was treated with antipsychotics and parenteral vitamin B12. Patient improved but some residual weakness persisted in lower limbs after 10 days of parental treatment with Vitamin B12.