Multiple Sclerosis (MS) is an inflammatory demyelinating disease that affects the white matter of the central nervous system. It’s more frequent in women. The disease has clinical heterogeneity, but initial neuropsychiatric symptoms are common (60%). If these symptoms are not present at the onset, they will certainly develop throughout the course of the disease.

To describe the case of a central hospital psychiatric inpatient and it’s comparison with the international available literature.

Retrospective analysis of the clinical process.

Woman, 51 years old, functioning until 3 months ago. Hospitalized for behavioral changes with heteroaggressiveness (verbal and physical) and psychomotor agitation. History of relapsing-remitting type MS with 10 years of evolution, treated with 44μg Interferon beta 1a (subcutaneous). To the mental examination she presented with uncooperative and suspicious attitude, dysphoric and delusional mood, changes in thought content with auto-referential/persecutory delusions and delusional interpretations. The extended analytical study, CE-CT and MRI were not altered, as were the Internal Medicine and Neurology evaluations. There was complete regression of symptoms after Interferon beta 1a suspension and maintenance of low-dose neuroleptic.

This is a rare case of psychotic disorder secondary to the use of interferon beta 1a in patients with MS. The rarity of this case is well patented as there is no published report of psychosis secondary to use of subcutaneous formulation, although it is known that psychiatric symptoms may occur in less than 1% of patients using this drug.