 Autoimmune hemolytic anemia, a condition in which the immune system attacks the red blood cells, is also more common in Crohn's disease and may cause fatigue, a pale appearance, and other symptoms common in anemia.Clubbing, a deformity of the ends of the fingers, may also be a result of Crohn's disease.Finally, Crohn's disease increases the risk of osteoporosis, or thinning of the bones.