Others have also recognized the value of CSF HS as a predictive marker of clinical efficacy (17); unfortunately, i.v. delivery of recombinant N-sulfoglucosamine sulfohydrolase resulted in no resolution of hepatosplenomegaly and no clear clinical benefits in a clinical study involving 6 patients with MPS IIIA. The gene discussed is SGSH; the disease is mucopolysaccharidosis type 3A.