Atlantoaxial instability in mucopolysaccharidosis type VII.

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.