Stiff-person syndrome

Stiff-person syndrome, also called stiff-man syndrome, is a rare neurological disorder of unclear cause in which the muscles grow progressively rigid and stiff. The trunk is affected first, and repeated spasms can bend the spine into abnormal postures, with a pronounced inward curve of the lower back, chronic pain and reduced mobility. It affects roughly one person in a million and is most often found in middle-aged adults. Most patients carry antibodies against glutamic acid decarboxylase, an enzyme involved in making the calming neurotransmitter GABA, although these antibodies are rare in the general population and are not proven to be the sole cause. A small minority of cases are paraneoplastic, linked to a tumour elsewhere in the body. The syndrome was first described in 1956. Diagnosis rests on clinical findings, antibody tests and electromyography, and treatment relies mainly on benzodiazepine drugs for relief of stiffness, with baclofen, intravenous immunoglobulin and rituximab also used.