There is no one who specializes in SA/CRS, as it is a rare condition with multiple medical types of treatment.  The list of doctors typically seen for treatment of SA/CRS are:

Urologist to address bladder and kidney (sometimes a nephrologist in the case of severe kidney issues)

Orthopedist to address treatment of hips, legs, knees, and feet

Gastroenterologists/colorectal specialists to address issues of the GI track and bowels

Neurologist to address issues of the spine and spinal cord

Physical Therapist to address mobility skills and wheelchair selection

Genetisist if there are other specific conditions that may be genetic such as Curarino syndrome (genetic factors for SA/CRS specifically are unknown)

Orthotist to construct and fit leg and foot braces

Nutritionist if there are concerns related to diet