A rare disease is any disease that affects a small percentage of the population. Rare diseases can vary in prevalence between populations, so a disease that is rare in some populations may be common in others. This is especially true of genetic diseases and infectious diseases. In this book, the authors present current research on the diagnoses, challenges and developing treatments for rare diseases, from researchers across the globe. Topics discussed include commotio cordis, also known as cardiac concussion with described cases of ventricular fibrillation and sudden death from cardiac arrest; the clinical manifestations and pathophysiology of muscle-specific kinase (MuSK) myasthenia gravis (MG); neurological complications of histiocytosis; nail-patella syndrome; management of cardiac angiosarcoma; diagnosis and treatment of clear cell adenocarcinoma of the bladder; eosinophilic pancreatitis; non-traumatic splenic rupture; and alkaptonuria (AKU).