Complex sentence: In longstanding cases and in patients who have taken iron supplementation or received numerous blood transfusions, iron overload may be a significant problem, being a potential cause of cardiomyopathy and liver disease.
Split into simpler sentences: In longstanding cases and in patients who have taken iron supplementation or received numerous blood transfusions, iron overload may be a significant problem. This is a potential cause of cardiomyopathy and liver disease.