Blood cell disorders affect red and white blood cells and smaller circulating cells called platelets. All three cell types form in the bone marrow, which is the soft tissue inside bones. Red blood cells transport oxygen to the body’s organs and tissues. White blood cells help fight infections. Platelets help the blood to clot. Blood cell disorders impair the formation and function of one or more of these types of blood cells. Symptoms may include fatigue, shortness of breath, difficulty concentrating due to lack of oxygenated blood in the brain, muscle weakness and elevated heartbeat. Blood tests can reveal blood cell disorders and treatment depends upon the cause and the cells affected.