Ultrasound assessment of diaphragmatic structure and function before and after orthotopic liver transplantation in MNGIE

Background: Mitochondrial Neurogastrointestinal Encephalomyopathy (MNGIE) is an ultra-rare autosomal recessive disorder caused by thymidine phosphorylase (TP) deficiency, leading to systemic nucleoside accumulation and multisystemic dysfunction. While respiratory failure is not a primary feature, severe cachexia, sarcopenia, and respiratory muscle weakness may contribute to morbidity, particularly during acute illnesses. Orthotopic liver transplantation (OLT) has emerged as a disease-modifying therapy, restoring TP activity and normalizing circulating nucleosides, though its impact on respiratory muscle function remains largely unexplored. Diaphragmatic ultrasound offers a noninvasive tool to monitor respiratory muscle structure and function longitudinally. Methods and results: We report a 27 year-old male with genetically confirmed MNGIE who underwent OLT while severely cachectic (BMI 13.4 kg/m2). Pre-transplant diaphragmatic ultrasound demonstrated severe atrophy (thickness 1 mm) and dysfunction (thickening fraction < 10%). Seven years after OLT, diaphragmatic trophism and contractility had markedly improved (thickness 2.3 mm; thickening fraction 31%), whereas peripheral skeletal muscle recovery remained limited. During a subsequent septic episode, the patient required only brief mechanical ventilation, reflecting enhanced respiratory resilience. Conclusions: Orthotopic liver transplantation provides sustained metabolic correction in MNGIE, facilitating significant recovery of diaphragmatic structure and function, even in patients with advanced disease. Diaphragmatic ultrasound proved invaluable for the noninvasive assessment of respiratory muscle trophism and contractility, guiding ventilatory management and long-term follow-up. Importantly, this case demonstrates a dissociation between peripheral and diaphragmatic muscle recovery, suggesting differential responsiveness to post-transplant metabolic normalization. These results underscore the potential of diaphragmatic ultrasound as a sensitive functional biomarker in MNGIE, although larger studies are warranted to establish its prognostic and clinical relevance.