Mucopolysaccharidosis Treatment & Management

Specific treatment or cure is limited for MPS. Management has been limited to supportive care and experimental treatment modalities. Routine assessment of multiple organ involvement is necessary to maintain the highest quality of life in these patients. Below are some of the medical and surgical treatment modalities that have been attempted for care of the patient with MPS.^{[5, 11, 12, 10, 8, 13]}

Laronidase (Aldurazyme) is a polymorphic variant of the human enzyme alpha-L-iduronidase produced by recombinant DNA technology. It is indicated to treat MPS type I (Hurler and Hurler-Scheie forms). It increases catabolism of glycosaminoglycans (GAGs), which accumulate with MPS I. Laronidase therapy has shown to improve walking capacity and pulmonary function.

Idursulfase (Elaprase) is a purified form of human iduronate-2-sulfatase, a lysosomal enzyme. It hydrolyzes 2-sulfate esters of terminal iduronate sulfate residues from the GAGs dermatan sulfate and heparan sulfate in the lysosomes of various cell types. It is used to replace insufficient levels of the lysosomal enzyme iduronate-2-sulfatase in MPS II.^{[14, 12, 10, 8]}

• Hearing loss: Severe handicapping hearing loss is present in about 70% of patients with MPS. Routine audiologic assessment and management is extremely important in order to maintain the highest quality of life.
• Joint stiffness: Range of motion exercises at home are indicated to limit the progressive loss of motion that is commonly seen in these patients. Night splinting and occupational aids have also been helpful.
• Bone marrow transplantation (BMT) has been successful in the treatment of MPS conditions, especially Hurler syndrome. Children treated with BMT generally have an increased lifespan compared to untreated children. Untreated children commonly died of cardiorespiratory compromise in the first decade of life. However, the musculoskeletal condition (dysostosis multiplex) did not improve with BMT. Skeletal radiographs of children treated with BMT and those who are not treated typically look similar.^[13]

Surgical care for specific conditions includes the following:

• Hydrocephalus: Ventriculoperitoneal shunting is the surgical treatment of choice in the child with hydrocephalus. Some clinical improvement has been noted in these patients after shunting. However, neurologic dysfunction has not been significantly affected. Thus, early recognition of hydrocephalus and early shunting before the onset of severe neurologic involvement may play a role in the management of these patients.
• Corneal clouding: Corneal transplantation has been performed for severe cases, but long-term results are lacking.
• Cardiovascular disease: Valve replacement has been performed, but experience is only limited. Mitral and aortic valves are most affected.
• Obstructive airway disease: Sleep apnea is common in MPS and is defined as cessation of airflow through the mouth or nose for a period greater than 10-15 seconds. Tracheostomy has been attempted for management of severe apnea with good success. Patients with obstructive airway disease are at a significant risk for anesthesia. This is especially true for patients with atlantoaxial instability such as those with Morquio syndrome.
• Orthopedic conditions: Orthopedic surgeries include soft tissue and bony procedures. The most common soft tissue procedure done in these patients is carpal tunnel release. Soft tissue procedures about the hip, knee, and ankle for release of contractures have also been performed, although results have been poor. Hip containment surgeries, such as femoral and pelvic osteotomies, are sometimes necessary in these patients. Progressive valgus deformity at the knee may also require corrective osteotomy, usually of the proximal tibia. Kyphosis is progressive in many of these patients, especially at the thoracolumbar level and sometimes associated with thoracis scoliosis. Posterior spinal fusion is proved to prevent further progression. In the cervical spine, odontoid hypoplasia can be seen leading to atlantoaxial instability. Fusion from C1 to C3 can be helpful.

Multispecialty care is mandatory for these patients and should include a pediatrician (internist), a neurologist, a cardiologist, an ophthalmologist, an audiologist, an orthopedic surgeon, and a physical and occupational therapist.