Fragile X disorders include two distinct conditions: fragile X syndrome (the most common single-gene cause of developmental delay and autism) and an entirely separate group of premutation syndromes.

What is patellofemoral pain syndrome (PFPS)? Patellofemoral pain syndrome (PFPS), also known as runner's knee, means that you have pain in front of the knee or around the kneecap (patella). This is ...