Clinical features and genetic characteristics of children with tyrosine hydroxylase deficiency caused by TH gene variants / 中华实用儿科临床杂志

ABSTRACT

Objective:To summarize the clinical characteristics and genetic features of tyrosine hydroxylase deficiency(THD) caused by TH gene variants for the improvement of the understanding of the disease. Methods:The clinical and genetic data of 33 children with THD caused by TH gene variants were diagnosed in the Department of Neurology of Beijing Children′s Hospital, Capital Medical University from May 2011 to January 2020 and their data were retrospectively collected and analyzed. Results:There were 19 females and 14 males.The age at onset was ranged from 0 to 6.3 years.13 patients developed diseases, accompanied with fever after infection, and 1 patient suffered from hypoxia, 19 patients suffered from no predisposing factors.There were 7 mild TH-deficient dopa-responsive dystonia cases, 16 severe TH-deficient infantile parkinsonism with motor delay cases and 10 very severe TH-deficient progressive infantile encephalopathy cases.Clinical symptoms were fluctuating, including 26 cases of diurnal fluctuation, 22 cases of infection aggravation, and 30 cases of fatigue aggravation.The initial symptoms included tiptoeing and numbness in the limbs(7 cases), motor development retardation or degression (26 cases), fremitus (8 cases), ptosis (2 cases), and status dystonicus (3 cases). Other clinical features had hypermyotonia (23 cases), hypomyotonia (27 cases), decreased movement (27 cases), decreased facial expression (24 cases), fremitus (18 cases), tiptoeing (20 cases), talipes equinovarus (7 cases), ptosis (8 cases), oculogyric crisis (10 cases), salivation (21 cases), dysphagia (12 cases), dysarthria (16 cases), dyspnea (3 cases), increased sleep (10 cases), decreased sleep (5 cases), irritable mood (15 cases), apathetic mood (2 cases), profuse sweating (8 cases), and status dystonicus (6 cases). A total of 6 patients′ right limbs were more severe, and 14 patients′ lower limbs were more severe.Eight patients had family history, and Levodopa treatment was effective for all patients.Ten patients suffered side effects, including dyskinesia and irritability.Four patients were lost follow-up, and 29 patients were followed up between 0.8 and 13.2 years old until Ja-nuary 2020.Totally, 22 patients almost had no such symptoms.Twenty-five TH gene pathogenic variants were discovered in 33 patients.There were 13 novel variants (c.1160T>C, c.1303T>C, c.887G>A, c.1084G>A, c.1097A>T, c.734G>T, c.907C>G, c.588G>T, c.992T>G, c.755G>A, c.184-6C>T, c.1510C>T, c.910G>A) and 2 patients had c. 910G>A variant.Meanwhile, there were 5 hot variants [c.698G>A(13 cases), c.457C>T(9 cases), c.739G>A(6 cases), c.1481C>T(4 cases), c.694C>T(3 cases)]. c.910G>A(2 cases) may be the foun-der variant of Chinese population. Conclusions:THD caused by TH gene variant mostly onsets from infant, with complex clinical features.Most of these patients were severe, and only a few were very severe and mild.Very severe and mild symptoms were easily misdiagnosed.Levodopa treatment was obviously effective.A possible founder variant of Chinese population (c.910G>A) was found.c.698G>A and c. 457C>T mutations mainly appeared in patients with severe and extremely severe THD, while c. 739G>A mainly appeared in patients with mild THD.