Late-onset Nonketotic Hyperglycinemia with Leukodystrophy and an Unusual Clinical Course

Late-onset nonketotic hyperglycinemia is very rare, presents with varied clinical features, and may be underdiagnosed. A 2-year-old girl with normal development had acute gait disturbance progressing to severe spastic diplegia. Plasma glycine levels were elevated, with a normal cerebrospinal fluid:plasma glycine ratio. Cranial magnetic resonance imaging revealed leukodystrophy. Nonketotic hyperglycinemia was confirmed enzymatically. At age 7 years, she cannot walk, but has borderline normal intelligence. Leukodystrophy and a normal cerebrospinal fluid:plasma glycine ratio were not previously reported in late-onset nonketotic hyperglycinemia.