PROGRESSIVE ENCEPHALOMYELITIS, RIGIDITY, AND MYOCLONUS: A NOVEL GLYCINE RECEPTOR ANTIBODY

TLDR

Progressive encephalomyelitis with rigidity and myoclonus (PERM) is a rare subacute disorder characterized by limb and truncal rigidity, muscle spasms, brainstem signs, and hyperekplexia, and is part of the stiff‑person syndrome spectrum with anti‑GAD antibodies in up to 80 % of patients and may be paraneoplastic with anti‑amphiphysin antibodies. The authors report a patient with typical severe PERM associated with a novel anti‑glycine receptor antibody. They describe a 54‑year‑old man who developed progressive limb and trunk rigidity, myoclonus, and respiratory failure, whose CSF showed lymphocytic pleocytosis and a slightly elevated IgG index, normal MRI, and who was ultimately found to have a novel anti‑glycine receptor antibody. Clinical summary.

Abstract

Progressive encephalomyelitis with rigidity and myoclonus (PERM) is a rare disorder of subacute onset presenting as limb and truncal rigidity, muscle spasms, brainstem signs, and hyperekplexia.1 Life-threatening, it is part of the spectrum of stiff-person syndrome (SPS) with anti-glutamic acid decarboxylase (GAD) antibodies in up to 80% of patients.1 It may also be paraneoplastic with anti-amphiphysin antibodies.2 Mutations in the α1 subunit of the glycine receptor gene GLRA1 have been identified in hereditary hyperekplexia.3 Glycine receptors are concentrated in the caudal pontine brainstem and spinal cord; in PERM, hyperekplexia (brainstem myoclonus or excessive startle)4 implies disruption of the normal inhibitory glycinergic mechanism in the caudal pons where the nucleus reticularis pontis caudalis mediates the startle reflex. We report a patient with typical severe PERM associated with a novel anti-glycine receptor antibody. ### Clinical summary. A 54-year-old man presented in January 2001 with 3 weeks of left flank tingling and 2 weeks of worsening brief frequent violent jerks, spontaneous and triggered by sensory and auditory stimuli; his upper limbs would abduct and flex and his trunk and legs extend. Neurologic examination was otherwise normal; he was intubated and ventilated. The CSF contained 60 lymphocytes × 109/L, the CSF IgG index was 0.72 (n < 0.7), oligoclonal bands negative. Cranial and spinal MRI scans with gadolinium were normal. After …