Background and aims: Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an immune-mediated disease with symmetrical motor and sensory manifestations, specific electromyographic (EMG) characteristics and diverse evolution: progressive, recurrent remissive, monophasic. In up to 1/3rd of cases the disease can manifest with demyelinating involvement of the central nervous system (CNS), and in up to 18% of patients it may have an acute onset as in Guillain-Barre syndrome (GBS). Methods: We present the clinical case of a patient with acute onset CIDP with CNS involvement. Results: Male of 27 years, previously healthy, was hospitalized with flaccid tetraplegia, areflexia, pain along the spine and limbs, facial asymmetry. The clinical manifestations evolved over several days. Brain MRI revealed periventricular demyelinating lesions, suggestive for multiple sclerosis. It was initiated pulse therapy with methilprednisolone without any improving. The cerebrospinal fluid (CSF) examination was acellular with increased level of proteins and positive oligoclonal bands. EMG revealed typical signs of demyelination. It was administered plasma exchange (PLEX), subsequently IVIG with partial recovery of motor functions. After 6 months his condition worsened again to the level of tetraplegia. CSF examination showed proteo-cellular dissociation, MRI examination foci of cerebral and cervical demyelination with gadolinium enhancement. Finally, the diagnosis of atypical CIDP was established. It was applied PLEX and later Prednisolone 1mg/kg/day with rapid regression of symptoms and signs, with almost full recovery 2 months later. Conclusion: GBS-like onset, brain and cervical spinal cord demyelinating lesions on MRI and CSF positive oligoclonal bands could contribute to the delay of atypical CIDP diagnosis. Disclosure: Nothing to disclose