Introduction The stiff person syndrome it’s a rare and not common neurological disorder, of unknown aetiology. There have been more than over 250 cases in the last 30 years. It consists in a long-term evolution of progressive muscle rigidity, with painful muscle spasms, mainly axial and pelvic limbs that lead progressively to disability, associated comorbidity and death due to complications. Symptoms generally start between the 4th and the 5th decade of life.

Methods 39 years old worker, purified water seller, 2 years in service, with 20 Kg weight lifting. He begins with lumbar pain that doesn’t respond to regular treatment; continues with decreased movement due to muscle rigidity, beginning with the upper extremities, moving forward to the pelvic limbs, with myoclonus and chorea, relating the symptoms to physical activity or stress that persists at rest. Physical examination: a slow and assisted walked was observed. Hypertonic lower limbs; presented myoclonus. Abolished reflections, strength and sensibility preserved. Myoclonus presented during examination with stiffness lower limbs, following walk tests. He continued without responding to treatment. Diazepam medication is added so he could fall asleep. He remains bedridden, performing only needed movements, with pain aggravation while presenting spasms.

Results Electromyography compatible with cervical and lumbar radiculopathy. Magnetic resonance without alterations. No Anti GAD test taken, considering only normal clinical description, laboratory data and consultancy results for diagnosis of the patient was stablished as stiff person syndrome with myoclonus version, determining incapacity due to a low compatibility with his job.

Discussion Progressively severe muscle stiffness typically develops in the spine and lower extremities; often beginning during a period of emotional stress. To make a right stiff man diagnose normality data in imaging studies are needed, laboratory data not concluding from another pathology, and relating clinical description. Anti GAD is presented only in 60% of the patients.