While there is a significant focus on neurodegenerative symptoms, it is important to recognise that all body systems are affected by Sanfilippo. Symptoms involving the skeletal system, including hip and backbone problems, have been reported in Sanfilippo patients. This has also been seen in a recent paper from Dr Nicole Muschol's group at the International Center for Lysosomal Disorders in Hamburg, Germany. Dr Muschol and her team found high rates of hip problems in patients with Sanfilippo, especially those with severe disease.
The team looked at medical records from 32 Sanfilippo patients who ranged from three to 27 years of age. Patients were classified based on their disease severity using genetic or other laboratory results. Then, hip abnormalities were assessed using X-ray images on file.
The hip joint is the meeting point of the top of the long thigh bone of the leg (called the femoral head) and the hip socket on the pelvic bone. Usually, the femoral head aligns with the hip socket; hip dysplasia is a condition where the femoral head and hip bone do not fit together well, often leading to hip dislocations. After evaluating the X-rays of the 32 Sanfilippo patients, the team found hip dysplasia in 28% of the patients, all of whom had severe disease.
Another condition affecting the hip is osteonecrosis of the femoral head, which involves the death of the top of the thigh bone. This was seen on the X-rays of 17 patients, and 13 of them had osteonecrosis of both hips. It was found that patients with severe disease were more likely to experience osteonecrosis of the femoral head.
The researchers also received information from parents and caregivers on potential pain experienced by the patient and any observed changes in walking patterns. Alarmingly, they found that perceived hip pain was reported in only 29% of osteonecrosis cases, indicating that it may be difficult to determine the presence of hip problems in Sanfilippo patients without clinical examination.
Although this study shows Sanfilippo patients may have an increased risk of developing hip problems, it is uncertain what causes these conditions. For example, the team notes that it may be due to the accumulation of the complex sugars, or possibly a by-product of inflammation or other effects.
As a result of this study, the researchers highly recommend using hip X-rays in routine and follow-up assessments of patients with Sanfilippo. Furthermore, this research demonstrates the importance of not focusing solely on the devastating neurodegenerative aspects of the disease, but also on treatments that can work throughout the body to improve overall quality of life.