Internal medicine or general internal medicine is the medical specialty dealing with the prevention, diagnosis, and treatment of internal diseases. Physicians specializing in internal medicine are called internists. Internists can manage particularly multisystem (affects a number of organs, or the whole body) chronic diseases or comorbidities that single-organ-disease specialists may not be trained to deal with. Moreover, they can manage undifferentiated presentations that cannot be easily fitted within the expertise of a single-organ specialty (e.g. dyspnea, fatigue, weight loss, confusion, …etc). Furthermore, they can manage serious acute illnesses that affect multiple organ systems at the same time in a single patient.