Facial onset sensory motor neuronopathy (FOSMN) is a rare disorder characterized by sensory deficits in the trigeminal territory associated with weakness and wasting of facial muscles [1]. Symptoms usually spread to neck and upper limb (UL) muscles. Usually, the disease duration is slowly progressive [1, 2]. In past reports, temporary response to intravenous immunoglobulin (IVIG) or plasmapheresis (PE) in some patients suggested an inflammatory pathogenesis [2, 3]. More recently, pathologic studies indicated a neurodegenerative mechanism [4]. We describe a rapidly progressive case of FOSMN mimicking amyotrophic lateral sclerosis (ALS). A 70-year-old man presented to our hospital with left UL weakness. He reported a 1-month history of paraesthesia and numbness in left side of face with loss of taste. Two weeks later, numbness involved scalp and neck. At the admission, neurological examination revealed moderate wasting of temporal and masseter muscles, especially the left ones. Fasciculations were present in facial and proximal limb muscles. He had also moderate weakness of neck flexors and trunk muscles, and slight weakness of left arm abductors and flexors. Pinprick and temperature sensation were reduced in the left trigeminal nerve territory. His general laboratory workup including serum lipoproteins, hormones and autoantibodies was unrevealing. Genetic testing for Kennedy’s disease was negative. Cerebrospinal fluid (CSF) analysis revealed 95 mg/dL protein with no oligoclonal bands. Nerve conduction studies (NCS) were normal, needle electromyography (EMG) revealed fibrillations in the left trapezius muscle and denervation-reinnervation changes in the muscles of the upper and lower limbs. Blink reflex showed delayed responses bilaterally. Motor evoked potentials showed an increase of central conduction time. MRI of the brain and spinal cord appeared normal with no evidence of syrinx or malignant roots infiltration. Because of the CSF protein increase, IVIG (2 g/kg in 5 days) was administered. Few weeks later, the patient experienced a subjective improvement in left UL muscle strength, however his overall condition at neurological examination remained unchanged. Two months after disease onset, facial pain increased, becoming continuous and stabbing. Left facial nerve palsy with severe weakness of neck flexors and moderate involvement of proximal and distal left UL muscles was evident. After 9 months the patient’s clinical condition continued to worsen, despite a five PE protocol. Common analgesics, pregabalin, amitriptyline, carbamazepine, tapentadol and tramadol were used in order to treat pain, with poor results. Weakness spread up to the territory of both facial nerves E. Barca (&) M. Russo A. Mazzeo C. Terranova A. Toscano P. Girlanda Department of Neurosciences, University of Messina, Messina, Italy e-mail: emanuelebarca@hotmail.com