In pancreatic acinar atrophy (PAA) a selective destruction of digestive enzyme-producing acinar cells leads to maldigestion signs typical of exocrine pancreatic insufficiency (EPI). Although the clinical disease is well-known, the etiopathogenesis of PAA has been long remained obscure. German shepherd dogs and rough-coated Collies with PAA show similar genetic, clinical and pathological findings indicating a similar etiopathogenesis of the disease in these two breeds. In this review article the etiopathogenesis of PAA is discussed, including the current suggestion of autoimmune nature of the disease. The diagnostic methods for detection both early and end-stage exocrine pancreatic dysfunction are described, as well as the treatment options and prognosis.