This study is for people with pyruvate kinase (PK) deficiency, a rare kind of anemia where the body doesn't make enough healthy red blood cells. It's called an observational study because it watches people to see what happens without giving them any treatment. The goal is to learn more about this disease over time. The study will last up to 9 years, and you are followed for at least 2 years. Doctors will collect information about your health and treatments from your medical records once a year. You can join this study if you have been diagnosed with PK deficiency through genetic testing, which checks your genes for changes that cause the disease.

• Participants will not receive any treatment; the study is only for observation.
• You may need to have your medical data reviewed and shared yearly.
• Participation could last up to 9 years, but at least 2 years are required.