Expansion of the Phenotypic Spectrum of MNGIE: Lipodystrophy and Metabolic Alterations Associated with a p.Arg393_Val400dup TYMP Variant

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a rare autosomal recessive disorder caused by mutations in the TYMP gene, typically characterized by severe and progressive gastrointestinal and neurological manifestations. Recent reports have identified a subset of patients presenting with generalized lipodystrophy and metabolic abnormalities, suggesting that adipose tissue involvement may be an underrecognized feature of the disease. Herein, we report the case of a 16-year-old female carrying a previously described homozygous TYMP variant (c.1178_1201dup; p.Arg393_Val400dup), who presented during adolescence with generalized lipodystrophy, insulin resistance, hypertriglyceridemia, hepatic steatosis, and other metabolic complications. At diagnosis, she exhibited no overt neurological or gastrointestinal symptoms; however, electroneurography revealed subclinical peripheral neuropathy. This case broadens the phenotypic spectrum of TYMP-related disease by documenting a lipodystrophic and metabolic presentation associated with the p.Arg393_Val400dup variant. While TYMP mutations have been linked to lipodystrophy in rare cases, this specific variant had previously been reported only in the context of classical MNGIE, with no documented evidence of adipose tissue or metabolic derangement. Our findings highlight the importance of considering TYMP involvement in the differential diagnosis of atypical lipodystrophy syndromes, particularly when features suggest underlying mitochondrial dysfunction.