A 17 Year Old With Developmental Delay Presenting With Increasing Confusion and Imbalance.

Methylmalonic acidemia is an autosomal recessive genetic disorder primarily caused by defects in methylmalonyl-CoA mutase and cobalamin (vitamin B12) metabolism. These defects disrupt the tricarboxylic acid cycle and oxidative phosphorylation, leading to the abnormal accumulation of metabolic products such as methylmalonic acid, propionic acid, and methylcitric acid. This accumulation results in damage to multiple systems, including the nervous, hepatic, and renal systems. Tethered cord syndrome results from pathological spinal cord traction due to congenital/acquired factors, causing conus medullaris malposition, neuronal degeneration, and progressive sensorimotor deficits. This report details a diagnostically complex case highlighting an unusual clinical intersection between these two conditions.