We report a 15-year-old boy with mucopolysaccharidosis (MPS) Type VII (Sly 
disease) who was found to have atlantoaxial instability with quadriparesis. 
Subluxation of C1 on C2 has also been documented in patients with Type I and 
Type IV MPS. Routine screening of the cervical spine is recommended in patients 
with "MPS Type VII" so that delayed diagnosis of instability, which may lead to 
neurologic compromise, is avoided.