[Clinical manifestation and gene analyses of 15 patients with intellectual disability or developmental delay complicated with congenital nystagmus].

Objective: To analyze the clinical and genetic features of 15 cases with intellectual disability or developmental delay (ID/DD) complicated with congenital nystagmus. Method: The clinical characteristics and the results of laboratory tests, images and genetics of 15 patients with ID/DD complicated with congenital nystagmus, confirmed by gene diagnosis in the Department of Neurology, Children's Hospital Affiliated to Capital Institute of Pediatrics from March 2015 to October 2016, were retrospectively analyzed. The physiological function of 13 disease genes and the molecular signaling pathways were also comparatively studied. Result: The patients included 11 males and four females, with an age of 2 months-15 years (median age 27 months). The result of multiplex ligation-dependent probe amplification was positive in two patients only with hypomyelination on head MRI. Positive results were found in 13 patients with or without abnormal head MRI or other deformities using targeted capture technology and next generation sequencing. Two patients were diagnosed with Pelizaeus-Merzbacher disease, two had hypomyelination with an atrophy of the basal ganglia and cerebellum and two had oculocutaneous albinism. Pelizaeus-Merzbacher-like disease was found in one case, cerebro-oculo-facio-skeletal syndrome in one case, Rubinstein-Taybi syndrome in one case, mental retardation type 5 in one case, methylmalonic aciduria combined with hyperhomocysteinemia in 1 case, ataxia telangiectasia in one case, hypomyelinating leukodystrophy type 8 in one case, Marinesco-Sjögren syndrome in one case and CHARGE syndrome in one case. A total of 12 novo mutations were reported in this study. Conclusion: The causes of children with ID/DD complicated with congenital nystagmusis are complex. Comprehensive clinical and auxiliary examinations should be performed to improve the accuracy of the diagnosis. Reasonable application of different genetic testing methods can significantly improve the diagnostic accuracy of molecular genetic etiology in children with ID/DD.