Light microscopic diagnosis of microvillus inclusion disease on colorectal specimens using CD10.

Microvillus inclusion disease (MID) is a rare neonatal enteropathy that is typically diagnosed using electron microscopy to show characteristic inclusions in conjunction with light microscopy and periodic acid-Schiff staining to show lack of the normal brush border on biopsies obtained endoscopically from the small bowel. MID has also been diagnosed using CD10 immunoreactivity that shows abnormal intense cytoplasmic staining in absorptive small bowel enterocytes. As ultrastructural studies also show abnormal microvillus inclusions in absorptive colonocytes in these patients, we investigated the use of CD10 immunoreactivity on colon specimens. We studied the CD10 staining pattern in 4 colon specimens from patients with MID and in colon biopsy specimens from pediatric control patients with and without histopathologic abnormalities. All MID cases had cytoplasmic CD10 staining in absorptive colonocytes in contrast to the control patients who did not show any epithelial CD10 staining. We conclude that abnormal cytoplasmic CD10 staining of absorptive colonocytes can aid in the diagnosis of MID, which may be invaluable in the situations where only colon biopsy specimens are available for examination.