A child who was unable to roll over and had weak neck muscles since 5 months of age. At 12 months, the child began to make sounds and crawl quickly; at 18 months, they started learning to sit and could stand against the wall but not for long, with poor balance. The child underwent the following examinations at Guangzhou Children’s Hospital: brain CT (normal plain scan), lumbar spine X-ray (normal plain scan), GCMS analysis showed large amounts of succinate, moderate amounts of pyruvate, lactate, and small amounts of fumarate in urine, MR imaging showed bilateral ventriculomegaly, karyotyping did not reveal any abnormalities, blood lactate was elevated (1.8), blood ammonia was normal (22), plasma acylcarnitine analysis showed elevated levels of amino acids such as glutamine, mitochondrial encephalomyopathy gene testing did not find the A3243G (MELAS), A8344G (MERRF), T8993G/C (LS) mutations. Please diagnose and treat.