How can a problem in one body system cause a cascade effect on multiple body systems? use anna as an example to illustrate your response.

This is a matter of cascading failure in which interrelated body parts are affected by dysfunctionality of each other. There is a zipper-like effect and the defect in one structural component leads to the production of compounds which affect other parts also, for example, ischemic cascade in which toxic are released which damage other body parts as well. 
In Anna's case, the splenic artery was affected by the sickle cells, which led to the accumulation of blood inside spleen and led to spleen sequestration. This further degraded her already present anemic condition, and the body was not able to receive ample nutrients from the blood supply and thus, kidneys were damaged severely, as the blood could not be filtered and high levels of toxins accumulated inside her body, which caused damage to other parts and her death also.

Ibelieve this would be an obstacle.