Glycine encephalopathy may encompass a spectrum of genetic mutations. One atypical variant results in late-onset manifestations precipitated by a febrile illness. Diagnosis in this group can be challenging if glycine encephalopathy is not considered.

Manifestations associated with a febrile illness may involve:

(1) intermittent chorea/choreoathetosis

(2) delirium

(3) vertical gaze palsy

(4) lethargy


Between infections they may manifest:

(1) mild decline in intelligence quotient (IQ > 60)

(2) attention deficit and hyperactivity disorder (ADHD)


Testing during an episode may detect abnormalities:

(1) elevated glycine in the CSF or brain

(2) abnormal enzyme activity

(3) gene mutation

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