Infants smile and follow and grasp objects, but they are unable to roll over or support weight on their legs. Generalized hypotonia and poor head control are present. Motor delay is usually more severe than cognitive delay. A wide degree of variability among patients with I-cell disease may exist. The characteristic facies is similar to that of Hurler syndrome.
Gingival hypertrophy is a distinguishing feature.
These findings are similar to those observed in Hurler syndrome, a condition with which I-cell disease may be confused. In early infancy, periosteal new bone formation leads to cloaking of the long bones. The tubular bones of the upper extremities are short and widened, and the phalanges are bullet-shaped. Anterior beaking and wedging of the vertebrae occur. This results in a lumbar gibbus deformity and kyphoscoliosis.