|Year : 2006 | Volume
| Issue : 2 | Page : 110-112
An uncommon presentation of hexosaminidase deficiency
Mary Iype1, Prabhakar Jyothy2, PR Sudhakaran2, Noel Narayanan3, Kunju PAM1
1 Departments of Pediatric Neurology, Government Medical College, Trivandrum, Kerala - 695 011, India
2 Departments of Pediatrics, Government Medical College, Trivandrum, Kerala - 695 011, India
3 Department of Biochemistry, University of Kerala, Trivandrum, Kerala - 695 011, India
TC 4/2559 (1), Pattom Kawdiar Road, Kawdiar PO, Trivandrum - 695003
Source of Support: None, Conflict of Interest: None
Focal muscular atrophy (FMA) can occur due to several causes. We report three cases of FMA associated with deficiency of hexosaminidase A. The serum level of hexosaminidase A was assayed in seven patients with FMA without any definite aetiology identified over a period of two years. Three cases of FMA showed deficiency of hexosaminidase A. All these patients had clinical features of isolated lower motor neurone involvement in one limb without any evidence of involvement of the rest of the neuraxis. Detailed laboratory tests were negative. Electromyography confirmed neurogenic involvement without any evidence of radiculopathy or neuropathy. Hexosaminidase deficiency as a possible association for FMA is highlighted.
Keywords: Focal muscular atrophy, Hexosaminidase A deficiency, monomelic amyotrophy, motor neuron disease, spinal muscular atrophy
|How to cite this article:|
Iype M, Jyothy P, Sudhakaran P R, Narayanan N, PAM K. An uncommon presentation of hexosaminidase deficiency. Ann Indian Acad Neurol 2006;9:110-2
| Hexosaminidase deficiency presenting as focal muscular atrophy|| |
Focal muscular atrophy (FMA) is not an uncommon presenting problem for patients attending neurological centres in India. A variety of etiological factors such as post polio paralysis, trauma, immune mediated plexopathies, toxins, electrical or radiation injury can account for FMA. In a hospital-based study from India, among 110 patients with anterior horn cell disease, 10.9% had progressive muscular atrophy; 1.8% had post polio muscular atrophy and 22.7% had monomelic amyotrophy, where the aetiology was not apparent. FMA of unknown aetiology referred to as monomelic amyotrophy is more often reported from India,, Korea and Japan. Hirayama et al had described a progressive wasting and weakness of the distal muscles of one upper limb which became arrested after 1-2 years.
Hexosaminidase deficiency (HD) has been associated with FMA and a spinal muscular atrophy (SMA) like syndrome., Tay Sach's Disease,, a progressive infantile encephalopathy, was the first neurological disease where HD was identified as the primary biochemical defect. Subsequently several other syndromes, such as progressive cerebellar ataxia resembling Ramsay Hunt syndrome, atypical spinocerebellar ataxia, resting tremor, dystonia, spastic paresis, psychosis and focal amyotrophy were reported in association with nonfunction/absence of hexosaminidase enzyme. Here we report three cases of FMA associated with HD.
| Case Report|| |
Between January 2003 and December 2004 we had come across seven cases of FMA of whom three were deficient for hexosaminidase. The diagnostic criteria of FMA were (1) wasting and weakness confined to a single upper or lower limb (2) progressive course or initial progression followed by a static course. (3) evidence of lower motor neuron (LMN) involvement only (4) no evidence of muscle or peripheral nerve disease (5) no involvement of bulbar cranial nerves, cognitive function, cerebellar, extrapyramidal, pyramidal and sensory system. The exclusion criteria included sudden onset and pain preceding the weakness, history of polio, herpes zoster, trauma, electrical injury, exposure to toxins or evidence of malignancy. Their muscle strength was graded using the MRC scale. Nerve conduction studies were done in the ulnar, radial, common peroneal and posterior tibial nerves (for motor); and median, ulnar and sural nerves (for sensory) by using the technique described by Kimura. We did electromyography in all patients using concentric needle electrodes. Spinal cord and root lesions were excluded using MRI scan of the corresponding spinal segments. Other investigations included a complete haemogram, blood sugar, urea, creatinine, chest X-ray, CPK, thyroid function tests and a collagen profile.
Hexosaminidase activity in serum was determined on samples drawn between 8 am and 10 am. The serum with age and sex matched healthy individuals, collected under identical conditions were used as controls. Hexosaminidase A and B activity was determined first. Repeat measurement after heat inactivation of hexosaminidase A yielded hexosaminidase B activity. Hexosaminidase A activity was calculated as the difference between total hexosaminidase AB and hexosaminidase B activities. Hexosaminidase A deficiency was defined as enzyme activity less than five percent compared to the age and sex matched control.
The clinical and electrophysiological details of these three patients of FMA associated with Hexosaminidase deficiency are given in [Table - 1][Table - 2]. MRI of the spinal cord was normal in all three patients.
| Discussion|| |
We presented three cases of FMA associated with HD identified from the neurological out patient service. All three cases were young females and presented with wasting and weakness restricted to a focal area, without any sensory abnormality. There were no clinically evident fasciculations, though two of them had fibrillations and positive sharp waves on electromyography. All patients had insidious onset, gradual progression and thereafter a plateau phase. No particular pattern of limb affection could be discerned since two cases had upper limb involvement and one had lower limb involvement. Selective involvement of the medial aspect of the forearm and small muscles of the hand and selective brachioradialis weakness had been reported in a cohort of cases of FMA. Diffuse atrophy of a limb as reported here, was earlier reported in 30 to 65% of FMA patients., Unlike in a previous report all the three patients were females.
Electromyography revealed a denervating process in the first two cases, with characteristic fibrillation potentials and positive sharp waves with the muscle at rest, decreased recruitment on minimal muscle contraction and an incomplete interference pattern on maximal voluntary effort. The third case also showed decreased recruitment on minimal muscle contraction and an incomplete interference pattern on maximal voluntary effort. The absence of giant and polyphasic motor unit potentials (MUP)s in all the three cases indicated the paucity of reinnervation in the denervated muscle.
Recently hexosaminidase deficiency had been reported in association with motor neuron disease, and SMA., We have reported three cases of FMA due to hexosaminidase A deficiency. Hexosaminidase A deficiency may be considered in cases of FMA when there is no evident cause.
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[Table - 1], [Table - 2]