Clinical features and laboratory characteristics of 4 cases of aromatic L-amino acid decarboxylase deficiency / 中华神经科杂志

ABSTRACT

Objective:To investigate the clinical characteristics, laboratory characteristics and genetic diagnosis of aromatic L-amino acid decarboxylase deficiency (AADCD), and to improve the understanding of this disease.Methods:Four children diagnosed with AADCD from the Department of Neurology, Beijing Children′s Hospital Affiliated to Capital Medical University from August 2016 to June 2020 were collected, and their clinical manifestations, laboratory and imaging data, and genetic test results were retrospectively analyzed.Results:All the 4 cases were diagnosed in early infancy, with the first symptom of feeding difficulties. They developed paroxysmal dyspraxia accompanied by eye movement crisis, movement regression, hypotonia, growth retardation, sleep disorders and autonomic nervous symptoms such as ptosis, excessive sweating and nasal congestion at the age of 2-4 months, respectively. The 4 children were siblings from 2 families with healthy parents. The dihydroxyphenylalanine decarboxylase ( DDC) gene mutations in cases 1 and 2 were derived from the maternal missense mutation c.1040G>A(P.RG347gln), and from the paternal deletion of exons 11 and 12, respectively. The DDC gene mutation in case 3 was derived from the maternal mutation c.419G>A(p.G140E) and the paternal mutation c.1375C>T(p.H459Y), respectively. Case 4 did not undergo genetic testing. Blood amino acid and acylcarnitine profiles and urine organic acid analyses were performed in 3 cases, and no specific abnormalities were found. In case 3, the results of 3-O-methyldopa (3-OMD) screening by blood dry filter paper increased significantly. Cerebrospinal fluid neurotransmitter detection results showed that the concentrations of 3-methoxy-4-hydroxyphenyldiol, vanillic acid and 5-hydroxyindoleacetic acid were significantly decreased, while the levels of 5-hydroxytryptophan and 3-OMD were increased in case 3. Blood aromatic L-amino acid decarboxylase (AADC) activity decreased significantly in case 3. Cranial magnetic resonance imaging (MRI) and electroencephalogram (EEG) examinations were performed in cases 1, 3, and 4, among which the cranial MRI in case 1 was normal, while the cranial MRI in cases 3 and 4 suggested that myelination was slightly backward. The EEG was normal in all the 3 cases. Cases 1 and 2 died of pneumonia and respiratory failure at the age of 1 year and 10 months. Case 3 was given clonazepam, benxel hydrochloride tablets and vitamin B6 tablets orally after diagnosis at the age of 4 months, and then treated with selegiline hydrochloride tablets and pramexol hydrochloride tablets. At the follow-up of 1 year and 6 months, the frequency of eye movement crisis and movement disorder was reduced, sleep was improved and autonomic nervous symptoms were alleviated, but there was no improvement in developmental delay. Case 4 was diagnosed with cerebral palsy and epilepsy, but failed various antiepileptic drugs and rehabilitation training, and died at the age of 10 due to heart failure and kidney failure. Conclusions:The clinical manifestations of AADCD are complicated and the misdiagnosis rate is high. Infants with early-onset hypotonia, developmental retardation, eye movement crisis, and movement disorders should be screened with dry filter paper as soon as possible for 3-OMD level, and suspicious cases should be diagnosed by cerebrospinal fluid neurotransmitter detection, plasma AADC activity determination, and gene examination. Early diagnosis of AADCD in children and gene mutation carriers can guide treatment and provide genetic counseling to reduce the incidence of the offspring.