Collagenous gastroenteritidesare rare disorders of unknown etiology diagnosed histologically by marked subepithelial deposition of collagen bands thicker than 10µm in the lamina propria with a mononuclear inflammatory infiltrate. Collagenous gastritis (CG) is divided into two phenotypes - pediatric-onset and adult-onset. Up until recently, pediatric-onset CG was thought to be confined to the stomach presenting with abdominal pain and anemia with limited involvement of the colon. Whereas adult-onset CG is often associated with involvement of the small and/or large intestine presenting with chronic non-bloody diarrhea and weight loss. It is now acknowledged that adult-onset and pediatric-onset CG should be considered a similar disease on a continuous spectrum. There are limited case reports of pediatric patients diagnosed as CG with concurrent collagenous duodenitis (CD) and/or collagenous colitis (CC). There are no accepted therapeutic standards for treating these patients. We present a rare case of an adolescent male with selective IgA deficiency and growth hormone deficiency presenting with severe iron deficiency anemia and abdominal pain with an ultimate diagnosis of collagenous gastroduodenitis with suspected jejunal involvement.