Carpal tunnel syndrome is a common musculoskeletal manifestation of Hurler’s syndrome. It can still occur despite treatment of the syndrome with a bone marrow transplant.

Hurler’s syndrome (mucopolysaccharidosis type 1H) is a lysosomal storage disease. It is caused by an autosomal recessive genetic deficiency of the enzyme α-l-iduronidase and has an incidence of around 1 in 100,000 live births [1]. This failure of normal lysosomal breakdown of complex carbohydrates produces a systemic accumulation of dermatan sulfate and heparan sulfate in tissues. The resulting clinical features include coarse facial features, proportionate short stature, progressive hepatosplenomegaly, cardiac and pulmonary failure, severe skeletal abnormalities, and progressive mental retardation. The musculoskeletal manifestations are the result of the accumulation of specific mucopolysaccharides in the cartilage, tendons, and joint capsule tissue. These may lead to carpal tunnel syndrome, triggering of the digits, shortened stature, thoracolumbar kyphosis, genu valgum, developmental hip dysplasia, generalized diminished enchondral ossification for longitudinal bone growth, and generalized joint stiffness [2, 3]. In untreated Hurler’s syndrome, the pattern of musculoskeletal abnormalities is referred to as dystosis multiplex and follows a typical course with premature death occurring at a median of around 5 years.

Since the early 1980s, treatment has consisted of a bone marrow transplant occurring before the age of 1 year. The donor bone marrow synthesizes the deficient enzyme which then diffuses into the tissues helping to prevent or reverse the accumulation of dermatan and heparan sulfate. This results in a reduction of any hepatosplenomegaly, an increase in cardiorespiratory function, an increase in intellect, and a longer life expectancy [2, 3]. The effect on the musculoskeletal manifestations of the disease is less marked due to reduced penetration of the tissues by the leukocyte-derived enzyme [2, 3]. In their sample of 43 children with Hurler’s syndrome, Khanna et al. found 53% developed carpal tunnel syndrome following bone marrow transplant [4]. A correlation between age at time of bone marrow transplant and the risk of developing carpal tunnel syndrome at a later date was also demonstrated. Each year, increase in age at the time of transplant produced a 58% increase in the risk of developing carpal tunnel syndrome [4].

Here, the case of a 7-year-old girl with Hurler’s syndrome is discussed. She initially presented with pins and needles affecting her left index and middle fingers after waking in the morning. She had received a successful sibling bone marrow transplant at the age of 10 months.

On examination, there was no thenar muscle wasting in either hand, but multiple flexor tendon nodules were palpable. The left index and right middle finger were noted to be triggering, with palpable nodules at the A1 pulley. The patient had good opposition of the thumb to little finger in both hands. On examination, no abnormality of sensation was detected. The patient complained of transitory numbness and pins and needles of the left index and middle fingers in the morning. An extensor lag of 5° was noted in all proximal interphalangeal joints and up to 10° in some distal interphalangeal joints. These were treated conservatively with splints and hand physiotherapy. Electromyography showed evidence of moderate to severe median neuropathy of both wrists, the left more severe than the right. Ultrasound showed no abnormality of the median nerve but there were significant deposits in the proximal interphalangeal joints resulting in an decreased joint space. An open left carpal tunnel release was performed, with simultaneous trigger-finger release of the left index finger. A standard incision was made over the flexor retinaculum. On decompression of the carpal tunnel, the flexor retinaculum was noted to be thickened, and the tunnel itself contained fatty-looking deposits. A hyperemic hourglass compression deformity of the median nerve was observed (Fig. 1). Six months later, the right carpal tunnel was released with simultaneous release of the right middle finger and thumb which were triggering. It was felt that performing the carpal tunnel releases of each hand separately would be less obstructive to the child’s development and education.

Fig. 1
figure 1

Intraoperative photo of the contents of the carpal tunnel following decompression. The hourglass deformity and hyperemia of the median nerve, highlighted by arrow, suggests marked compression

Full size image

At eighteen months sensation was normal in the thumb, index, or middle fingers of both hands. The patient was noted to be developing flexion contractures of the distal interphalangeal joints, these were correctable with gentle stretching, for which they were referred to hand physiotherapists for conservative management.