The Stiff-man Syndrome in Children and Adolescents

The stiff-man syndrome (SMS, also known as stiff-person syndrome) is an autoimmune disorder characterized by stiffness and spasms affecting muscles of limbs and/or axial regions. Rarely reported in childhood and adolescence, SMS may be underrecognized but should be considered in children presenting with a hypertonic or hyperekplectic phenotype. Presentations may include new onset attacks of focal or widespread stiffness and spasms, sometimes precipitated by anxiety, which may lead to falls. The lower extremities and lumbar spine are most commonly affected, but both focal and more extensive "whole-body" phenotypes are recognized. In addition to history and examination findings consistent with SMS, the following are supportive of the diagnosis: a history of autoimmune disease, detection of GAD65 or glycine receptor antibodies in serum or CSF, hyperexcitability on neurophysiological testing, and clinical improvements with benzodiazepines or immunotherapy. Although prognosis varies, most patients improve with treatment, highlighting the importance of early and accurate diagnosis.