Although carpal tunnel syndrome (CTS) is the most common compressive neuropathy seen in the upper extremity of adults, it is rarely seen in children. Several reports have shown that mucopolysaccharidosis type II (Hunter syndrome), a rare genetic disorder, is one of the causes of CTS in children. Usual symptoms of CTS are pain, weakness, and paresthesias in the hand and digits. However, the diagnosis of CTS in Hunter syndrome is often delayed or unrecognized because of atypical symptoms and cognitive impairment. Here, we report the prevalence, clinical manifestation, and nerve conduction profiles of CTS in 45 Hunter syndrome patients. The mean age of the study participants was 117.1 (74.9) months (range: 4-408 months); all patients were male. Forty-three (96.0%) of the 45 patients with Hunter syndrome had CTS. Bilateral CTS was observed in all patients; 73 (82.0%) of the patients' hands had severe degree of CTS. Intriguingly, in contrast with other nerve velocities, decreases in forearm conduction velocities of the median nerve were observed in 28 (31.5%) of 89 hands with CTS. There was a significant difference in age (P < 0.001) between hands with normal, mild, moderate, and severe grades of CTS. The compound muscle action potential and sensory nerve action potential amplitudes of the median nerves decreased with age (CMAP, r = -0.526, P < 0.001; SNAP, r = -0.564, P < 0.001). Early recognition and intervention to ameliorate the symptoms of CTS are important in improving the quality of life of Hunter syndrome patients.
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