Abstract
Progressive encephalomyelitis with rigidity and myoclonus (PERM) is a relapsing–remitting
neurological disorder that falls within the stiff person syndrome–spectrum disorders.
We report a 16-year-old girl with PERM associated with an anti-glutamic acid decarboxylase
(GAD) antibody. She had an aggressive initial presentation mimicking fulminant septic
shock, followed by truncal and lower limb rigidity, stimulus-sensitive spasm, cognitive
impairment, brainstem signs (hyperekplexia, nystagmus), and dysautonomia (urinary
retention, constipation, facial flushing, blood pressure fluctuation). Cerebrospinal
fluid, electroencephalography, and magnetic resonance imaging of the brain and spine
showed features suggestive autoimmune encephalitis and myelitis. The serum anti-GAD
antibody was positive, and the diagnosis of PERM was made. She had fluctuating clinical
response despite intravenous immunoglobulin, steroids, plasmapheresis, and symptomatic
medications. Eventually, in the fourth month since admission, she showed gradual and
persistent clinical improvement after introducing rituximab. She was discharged after
6 months of hospitalization, and no relapse was observed in the first 3 years of follow-up.
PERM is a rare and underrecognized condition in children. Contrary to previous reports,
our case describes an aggressive and life-threatening presentation for PERM. Vague
symptoms and the lack of gold diagnostic tests hinder a timely diagnosis. Our study
also highlights the need for developing standardized diagnostic criteria and consensus
in managing PERM.
Keywords PERM - stiff person syndrome - glutamic acid decarboxylase - dysautonomia
