Dr. Mack obtained his medical degree from the University of Toronto in 1983. He split his Pediatrics Residency training to both the Children’s Hospital of Eastern Ontario and Hospital for Sick Children and then completed Pediatric Gastroenterology Fellowship at the Hospital for Sick Kids.

His first appointment was to faculty at the University of Nebraska, School of Medicine in the United States in 1991 and he returned to Ottawa after 10 years in 2001 to undertake the development of a Division of Pediatric Gastroenterology at the Children’s Hospital of Eastern Ontario. Dr. Mack is currently a Professor with the Department of Paediatrics in the Faculty of Medicine at the University of Ottawa; Chief of Pediatric Gastroenterology, Hepatology & Nutrition at the Children's Hospital of Eastern Ontario; Director of the CHEO IBD Centre and Senior Scientist at the CHEO Research Institute.

Current research Interests are clinical aspects of Inflammatory Bowel Disease and understanding the role of the intestinal microbiome in their pathogenesis.