Clinical and imaging features of late-onset hyperphenylalaninemia leukoencephalopathy
Objective To explore the clinical and imaging features of late-onset hyperphenylalaninemia(HPA)leukoencephalopathy in untreated adolescents.Methods A total of five patients with adolescent-onset HPA,diagnosed by biochemistry and(or)gene in the Department of Neurology,Peking Union Medical College Hospital from January 2015 to January 2022 were selected,and the clinical and imaging features were analyzed.Results Among the five patients,there were three males and two females with the onset age of 7 to 15 years,and the diagnosis age was 14 to 20 years old.Clinical manifestations included mental retardation,psychobehavioral symptoms,spastic gait and seizures.The white matter lesions were centered in the parieto-occipital lobe adjacent to the posterior horn of the lateral ventricle,gradually spreading to the frontal lobe,the semi-oval center and the subcortical white matter,avoiding optic radiation and U-shaped fibers in the early stage.The lesions showed persistent DWI high signal without enhancement.In addition,there were mismatches between the white matter lesions seen on MRI and the actual clinical manifestations,and the mismatch between white matter lesions and cortical atrophy suggested gray matter involvement.After low phenylalanine diet treatment,the patient's neuropsychiatric symptoms remained stable,but the imaging lesions could still progress.Conclusions The onset HPA of adolescents is often characterized by mental retardation or spastic paralysis,with or without other nervous system symptoms.The distribution of imaging white matter lesions is centered on the white matter of parietal occipital lobe near the posterior horn of lateral ventricle,which can expand to a wider range with the severity of the disease.After diet control,the clinical symptoms can be stabilized,but the imaging lesions can continue to progress.Early diagnosis and treatment can improve the prognosis and quality of life of patients.