Ulcerative colitis in a child with mitochondrial disease: a case report

Gastrointestinal symptoms are recognized in mitochondrial disease; however, inflammatory bowel disease, particularly ulcerative colitis (UC), is exceedingly rare. Herein, we report a pediatric patient with genetically confirmed mitochondrial disease who presented with persistent UC-like colitis, suggesting the possibility of an association between mitochondrial dysfunction and intestinal inflammation. A 7-year-old boy with mitochondrial disease due to a homoplasmic m.14487T>C mutation in the MT-ND6 gene detected in leukocytes experienced persistent mucoid and bloody diarrhea. Colonoscopy revealed pancolitis with patchy mucosal involvement and a longitudinal ulcer, and biopsy revealed inflammatory changes with segmental crypt distortion. Despite these atypical features, the patient was managed under a working diagnosis of UC. Treatment with corticosteroids and 5-aminosalicylic acid achieved partial improvement, followed by complete remission with adalimumab. Later, he developed chronic intestinal pseudo-obstruction, requiring continuous enteral nutrition. Immunohistochemical analysis of intestinal mucosa consistently demonstrated reduced complex I expression, independent of inflammatory activity, aligning with the MT-ND6 mutation. Immunosuppressive therapy was well tolerated without systemic deterioration. In the present case, UC-like colitis may be associated with mitochondrial disease, specifically in the context of persistent complex I deficiency. The clinical and histological overlap with idiopathic UC, together with underlying mitochondrial dysfunction, suggests the need to consider mitochondrial disease in pediatric patients with atypical or treatment-refractory colitis. Immunohistochemical analysis of mitochondrial complexes may offer additional information to support diagnosis.