Bilateral carpal tunnel syndrome and multiple trigger fingers in a child with mucolipidosis Type III disease

Abstract

This report presents a five-year-old girl with mucolipidosis Type III disease who had bilateral carpal tunnel syndrome and eight trigger fingers. Bilateral open carpal tunnel release was performed. The trigger fingers were treated with A1 and A3 pulleys release and the ulnar slips of the flexor digitorum superficialis tendons were removed.

INTRODUCTION

Mucolipidosis Type III is an inherited lysosomal storage disease that all the enzymes are present, however, the targeting factors on the enzymes are deficient and the lysosomes are unable to recognize and transport the enzymes.[1–5] The enzyme deficiency in mucolipidosis Type III is mutations in UDP-N-acetylglucosamin: Lysosomal enzyme N-acetylglucosaminyl-1-phosphotransferase.[4,5]

The reported hand manifestations of mucolipidosis Type III include: Carpal tunnel syndrome (CTS), trigger digit, triggering at the wrist level, claw hand, clinodactyly, brachydactyly and generalized joint stiffness. They develop because of deposited substances in the different tissues including cartilage, bone, joint capsule, tendon, synovium and connective tissues. However the clinical manifestations may have varied severities.[6–8]

We present a five-year-old girl with mucolipidosis Type III disease who had bilateral CTS and eight trigger fingers.

CASE REPORT

A five year old girl presented with an inability to use her hands. Her parents had noticed that her problems began at the age of three years. All the fingers of her right and left hands were locked in extension. She could not flex the proximal and distal interphalangeal joints of her fingers actively. The locked positions of the fingers were not released by passive flexion. There were palpable nodules over the proximal phalanges of all her fingers. The thumbs movements were normal but she had thenar wasting.

Since mucopolysaccharidosis is a well-known cause of multiple trigger fingers in children her urine was analyzed to look for excretion of glycosaminoglycans which was negative. However, serum enzyme analysis revealed beta-glucoronidase 14.1564 mU/ml (norm: 0.281-1.991 mU/ ml); alpha-mannosidase 15.9537 mU/ml (norm: 0.10-0.262 mU/ml); beta–mannosidase 48.1079 mU/ml (norm: 3.918-11.65 mU/ml); total hexamin 229.6 mU/ml (norm: 8,916-27.07 mU/ml). The extreme high level of serum enzymes was compatible with the diagnosis of mucolipidosis Type III. In mucolipidosis Type III the abnormal enzymes are expelled from the cells and are present at high levels in the serum of the affected patients.[1,2,4]

The patient did not present symptoms of CTS probably because of the young age. Tinel's sign and Phalen's tests were negative. The patient was not cooperative to perform sensory testing. Electrodiagnostic screening for CTS has been recommended for all the children with mucopolysaccharidoses.[1–3] An electrodiagnostic study of her hands revealed bilateral severe CTS.

Under general anaesthesia, open carpal tunnel release was performed in both hands through midpalmar incision. The transverse carpal ligament was thickened. The median nerves had hourglass constriction [Figure 1]. External neurolysis was performed and the thenar branch explored. Tenosynovectomy was performed. Histopathology study of the flexor retinaculum [Figure 2] demonstrated foamy macrophages distributed between collagen fibres, compatible with the storage disease.

Figure 1.

The left median nerve shows hourglass constriction

Figure 2.

Histopathology study of the right flexor retinaculum demonstrates “balloon cells” (foamy macrophages) (black arrows) distributed between the collagen fibres, compatible with the storage disease. (Haematoxylin and Eosin, ×400)

To treat the trigger fingers, the flexor sheaths were approached and inspected through zigzag incisions over the palpable nodules in the fingers. During surgery the A1 and A3 annular pulleys appeared thickened and there were multiple nodular thickenings and fusiform swellings along the course of the deep and superficial flexor tendons proximal to the A3 pulleys preventing the excursion of the flexor tendons [Figure 3]. Trigger digits were treated by sequential A1 and A3 release and resection of the ulnar slip of the flexor superficialis tendons. The ulnar slips of the flexor digitorum superficialis (FDS) tendons were resected to open space for the movement of the flexor tendons.

Figure 3.

Multiple nodular thickening and fusiform swelling along the course of the ring finger's deep (black arrows) and superficial flexor tendons (white arrow) in the left hand

Intraoperative manual passive flexion and extension of the fingers and passive traction of the flexor tendons proximal to the A1 pulley and through the released carpal tunnel confirmed adequate release. However there were mild proximal interphalangeal and distal interphalangeal joints’ stiffness.

Histopathology study of the A1 [Figure 4] and A3 pulleys and the excised slip of the superficialis flexor tendons demonstrated foamy macrophages distributed between collagen fibres, compatible with the storage disease.

Figure 4.

Histopathology study of the right hand`s small finger's A1 pulley demonstrated abundant foamy macrophages (black arrows) distributed between collagen fibres, which suggest the storage disease. (Haematoxylin and Eosin, ×400)

After six months’ follow-up finger flexion improved considerably in both hands. The fingertips approached to 1 cm from the distal palmar crease [Figures 5 and 6].

Figure 5.

Post-operative clinical outcome: Extension of the fingers, surgical scars are apparent

Figure 6.

Post-operative clinical outcome: Flexion of the fingers

DISCUSSION

A prominent feature of this case is the silent development of severe CTS. It might develop secondary to the thickened flexor retinaculum, increased volume of the flexor tenosynovium, and abnormal anatomy of the carpal tunnel due to the dysplastic carpal bones.[2,7,8] The deposition of mucolipids in the median nerve has not been described.

In the children who present with trigger digits, congenital triggering should be distinguished from the triggering that develops in the lysosomal storage diseases. In the congenital trigger finger there is an abnormal flexor anatomy.[9–11] However, in the lysosomal storage diseases, as observed in this case report, triggering may develop because of enlargement of the flexor tendons and thickening of the annular pulleys secondary to accumulation of the deposited materials.[3,6,8]

In the children who present with locked fingers, the trigger finger should be distinguished from the joint stiffness and contractures by clinical examination (palpation of the nodule and active and passive movement of the interphalangeal joints) and intraoperative assessment of flexor tendon excursion.[3,9] In the lysosomal storage diseases joint stiffness and contractures might be developed because of deposition of materials in the cartilages, ligaments and joint capsules.[2]

There is no standard treatment to address the congenital trigger fingers in children.[9] The following echelons of treatment might be necessary until the full excursion of the tendon achieved: Release the A1 pulley, release the A3 pulley, partial division of the A2 pulley, widening of the FDS chiasm by separating the terminal slips of the FDS tendon in a proximal direction, partial resection of the superficial flexor tendon, resecting of both slip of the FDS tendon and suturing the sublimes tendon to the profundus tendon, and tenosynovectomy.[3,8–11]

Treatment of the trigger fingers in mucopolysaccharidosis depends on the surgical findings and judgment at surgery. Mac Doughal et al., advised the release of the fibro-osseous tunnel to treat the trigger finger in mucopolysaccharidosis and its related diseases. However, they did not point out exactly which anatomic structure should be released.[6] Haddad et al., performed A1 pulley release and limited synovectomy to treat the trigger finger in mucopolysaccharidosis and its related diseases.[8] Van Heest et al., advise intraoperative surgical judgment and sequential release of A1 and A3 pulleys and the partial resection of flexor digitorum superficialis tendon until the full excursion of the tendon is achieved.[3] In this case there were multiple nodules and thickening along both the flexor tendons and releasing the A1 and A3 pulleys was not adequate treatment for the trigger fingers. Therefore, the ulnar slips of the FDS tendons were resected for opening space for the movement of flexor the tendons.

There is limited information about the natural history and functional outcomes of the hand involvement in mucolipidosis Type III.[2,7,8] Currently there is no treatment for mucolipidosis III disease and she will continue to have abnormal metabolism. The five year old girl might develop recurrence in the future and may need further surgery if she lives long enough, although six months post operatively, hand functions had improved considerably.