Sandhoff disease is a rare autosomal recessive metabolic disorder of GM₂ gangliosides. Recently, a 10-month-old female child of nonconsanguineous marriage presented with developmental delay. She had attained social smile and approach to objects. There was no head control. She was not able to recognize her parents. There were no seizures. Vision and hearing were normal. However parents denied any deterioration in the neurological state. Growth parameters including head circumference were within normal limits. She had mild hypotonia. Deep tendon reflexes were normal and plantar responses were flexor bilaterally. She had bilateral cherry red spots in the fundus. Enzyme assay from two separate laboratories showed marked reduction of hexosaminidase A and B levels in the serum. Magnetic resonance imaging (MRI) showed unmyelinated large parts of white matter of centrum semiovale. Striking putaminal hyperintensity was seen on T₂ weighted images bilaterally (Fig. 1). Thalami also showed low signal on T₂ weighted images bilaterally.

Fig.1. Bilateral putaminal hyperintensity on T2 weighted images

Studies on magnetic resonance imaging in Sandhoff disease are scant in literature. However as early as in 1993, Caliskan, et al.(1) have suggested bilateral thalamic hyperdensity on computed tomography as a diagnostic marker of Sandhoff disease. Several other reports have shown involvement of thalamus, basal ganglia (caudate, putamen, globus pallidus) and cerebellum in this condition with rare involvement of other parts of brain(2-5). A review of these works suggests basal ganglia are more consistently involved than the other regions of the brain. Based on findings in three patients with GM₂ gangliosidosis Grosso, et al. have suggested that MRI pattern peculiar to GM₂ gangliosidosis can be defined(4). There have been a few attempts at clinical correlation with neuroimaging(3,4).

Our case shows further evidence to basal ganglia involvement in Sandhoff disease. We alert our fellow physicians involved in evaluation of neurometabolic diseases to look for these findings in more cases and perform enzyme assay when such lesions are noted on MRI. Any neuroimaging clue for the diagnosis of neurometabolic disorders are of paramount importance as diagnosis based on clinical information is very difficult and lack of access to biochemical assays in Indian scenario.

The authors thank Dr. Rajendra V. Phadke, Professor of Radiodiagnosis, Sanjay Gandhi Postgraduate Institute of Medical Sciences for the radiological evaluation.

K.M. Girisha,
Shubha R. Phadke,
Department of Medical Genetics,
Sanjay Gandhi Postgraduate Institute of Medical Sciences,
Lucknow 226 014, (U.P.), India.
E-mail: [email protected]

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