Adolescent-onset hyperhomocysteinaemia: cases report and literature review.

We summarize and review the clinical and genetic characteristics of four adolescents with Hyperhomocysteinemia. Four cases of adolescent-onset Hyperhomocysteinemia diagnosed at Qingdao University Affiliated Hospital were selected as research subjects. Clinical data, whole exome sequencing and Sanger sequencing information of the patients were collected, and gene variation analysis and literature review were conducted. The pathogenic variants carried by the four patients were MAT1A c.895C>T(p.Arg299Cys), CBS c.374G>A(p.Arg125Glu), CBS c.785C>T(p.Thr262Met), and MMACHC c.482G>A(p.Arg161Glu) and c.658_660del(p.Lys220del) along with other site mutations. There were three cases with epileptic seizures as initial manifestation, three cases with varying degrees of intellectual disability, two cases with lens dislocation, one case with cervical artery occlusion leading to cerebral infarction, and one case with extensive white matter lesions. Four patients showed relief of symptoms after treatment with vitamin B and necessary antiepileptic drugs. We combined the cases and relevant literature to retrospectively analyze the characteristics and treatment related to the disease. The onset of Hyperhomocysteinemia in adolescents is early, and the clinical manifestations are broad and atypical. At the same time, it has a significant impact on the growth and development of adolescents and can affect future life for a long time. Early detection and diagnosis have an important impact on prognosis.