BRIEF COMMUNICATION Tonic pupils: an unusual autonomic involvement in chronic inflammatory demyelinating polyneuropathy (CIDP) Marcio Luiz Escorcio-Bezerra 1 & Gilberto Mastrocola Manzano 1 & Denis Bernardi Bichuetti 1 & Karlo Faria Nunes 1 & Daniele Sales Alves Correa 1 & Acary Souza Bulle Oliveira 1 & Alex Machado Baeta 1 Received: 4 January 2019 /Accepted: 9 April 2019 # Fondazione Società Italiana di Neurologia 2019 Abstract Background Chronic inflammatory demyelinating polyneuropathy (CIDP) is a neuropathy which affects mainly large myelin- ated axons and has a typically mild autonomic dysfunction mainly from postganglionic nerve fiber involvement. Case report We report here an acute onset CIDP initially diagnosed as Guillain-Barré syndrome (GBS), unresponsive to treatment with intravenous immunoglobulin (IVIg), which later responded to plasmapheresis and corticoids. The patient had a markedly distal demyelination, prominent cranial nerve involvement and, interestingly, bilateral fixed dilated pupils. Despite complete clinical recovery, this neurological sign remained. Conclusions Tonic pupils have previously been described in different neurologic conditions, including GBS, but not yet in acute onset CIDP or in variants with predominantly distal demyelination. It differs from the classical Adie’ s pupil because it lacks the light-near dissociation. This case report expands the range of possible autonomic signs in acute onset CIDP, which could help physicians establish optimal treatment strategies earlier on. Keywords Chronic inflammatory demyelinating polyneuropathy . Adie’ s pupil . Tonic pupil . Autonomic dysfunction . Guillain-Barré syndrome . CIDP Chronic inflammatory demyelinating polyneuropathy (CIDP) is a clinically heterogenous neuropathy which develops over more than 8 weeks and has inflammatory-mediated demyelin- ation as pathological hallmark [1]. This disease involves mainly large myelinated axons while the autonomic dysfunc- tion is usually mild and predominantly sudomotor, resulting primarily from lesions at the distal postganglionic nerve fibers [2]. We present here a case of acute onset CIDP, with a pre- dominantly distal demyelination and cranial nerve involve- ment, which included bilateral dilated unreactive pupils due to parasympathetic denervation of the pupil sphincter muscles. A 23-year-old female house cleaner had watery diarrhea for about 3 days. One week later, she noted numbness in feet and progressive weakness in lower limbs, which in the following 5 days evolved to gait unsteadiness. She was hospitalized and initially diagnosed with Guillain-Barré syndrome (GBS). Intravenous immunoglobulin (IVIg) was administered. Even though no significant improvement was observed, she was discharged from hospital, as symptoms were mild at this point. In the following weeks, however, the weakness progressed and she developed diplopia and hoarseness, being readmitted to the hospital 5 weeks after symptoms onset. Her examina- tion revealed flaccid tetraparesis and muscle strength was Medical Research Council (MRC) scale grade 2 in proximal muscles and grade 1 in distal muscles from upper and lower limbs. Tendon reflexes were absent. There was bilateral facial palsy, bulbar weakness, and bilateral ophthalmoparesis. Pupils were dilated bilaterally and unresponsive to direct and indirect light stimuli (Fig. 1). Vision was blurry but visual acuity was grossly intact. Other symptoms or signs of dysautonomia were absent. There was distal hypoesthesia to all sensory modalities in the four limbs. Cerebrospinal fluid (CSF) analysis showed albuminocytologic dissociation (303 mg/dL protein). Routine laboratory tests were normal, including complete blood count, routine blood biochem- istry, glucose, copper and vitamins B1 and B12 levels, serum protein electrophoresis, rheumatologic antibodies, paraneoplastic * Marcio Luiz Escorcio-Bezerra marciobzrra@gmail.com 1 Department of Neurology, Escola Paulista de Medicina, Universidade Federal de São Paulo, Rua Pedro de Toledo, 650, São Paulo, SP 04039-002, Brazil Neurological Sciences https://doi.org/10.1007/s10072-019-03890-8