Lymphocytic and collagenous colitis in children and adolescents: Comprehensive clinicopathologic analysis with long-term follow-up.

Microscopic colitis (MC) is characterized by chronic watery diarrhea, endoscopically normal findings, and abnormal histology. While mostly encountered in adults, pediatric cases are rare and may show varying presentations. Our pathology data system was searched from 1984 to 2019 for patients ≤18 years of age with a lymphocytic colitis (LC) or collagenous colitis (CC) pattern of injury. Twenty-seven cases (23 LC and 4 CC) were retrieved. LC was more prevalent than CC (85% vs 15%, respectively) and affected slightly younger individuals (mean, 9.8 years versus 12.25 years). Immune dysregulation was documented in 11 (41%) patients. Most patients presented with watery diarrhea (n = 26, 96%) and either abdominal pain (n = 18, 67%), nausea/vomiting (n = 5, 19%), flatulence (n = 6, 22%), and/or weight loss (n = 1, 4%). A subset of patients (n = 10, 37%) demonstrated endoscopic abnormalities. Histologically, some patients with LC and CC displayed focal cryptitis or crypt abscess formation (n = 7, 26%) and focally increased crypt apoptosis (n = 9, 33%) in the absence of chronic injury. Clinical follow-up data were available for 23 (85%) patients with variable clinical responses recorded. Only 8 patients experienced complete symptom resolution. Twelve patients (11 LC and 1 CC) had subsequent biopsy material; of which, one developed histologic features of inflammatory bowel disease and another was found to have a CTLA-4 deficiency. Our study shows that pediatric patients with MC may have atypical clinical, histologic, and endoscopic findings and variable clinical responses. Underlying inflammatory and/or genetic conditions may be eventually unmasked, and genetic testing may be helpful in a small subset of patients.