Clear cell colitis: a form of microscopic colitis in children

Abstract

Aim: To describe a new clinical and pathological subtype of microscopic colitis in children.

Methods: A selected group of children with abdominal pain, constipation and/or diarrhoea showing discrete or no macroscopic abnormalities on endoscopy was described.

Results: Multiple biopsies of colon showed large mononuclear clear cells in lamina propria of mucous membrane provided that good quality histological sections were performed and observed under a higher magnification. Otherwise, they could be misinterpreted as artefacts. Their presence in routine histology might suggest a systemic storage disease (Whipple's disease), and neuronal intestine dysplasia. Using immunohistochemical staining and electron microscopy we confirmed their origin from CD68 positive mononuclear macrophages.

Conclusion: The presence of large clear cells is a constant microscopic feature. Failure of transient large bowel stationary macrophages plays a role in the pathogenesis of this benign microscopic clear cell colitis, sometimes coexisting with allergy.

Figure 1

Microscopic features of CCC (A-F) (HE, × 320).

Figure 2

Immunocytochemistry of CCC using monoclonal antibodies and APPAP method showing positive expression of mononuclear phagocytic cell line (A and B), negative T3 and T4 lymphocytes (C), negative neurofilament (D), Normal PCNA expression in cryptal epithelium (E), and normal mitotic activity of positive CD67 (F) (× 320).

Figure 3

Electron microscopy of clear cells. Giant clear macrophages contain multiple vesicles varying in size filled with homogenous osmiophylic materials (secondary phagosomes) without any structural components in their cytoplasm (OsO₄ staining, × 24 000).