ABSTRACT
Infantile GM 1 or generalized gangliosidosis is a lysosomal
storage disease in which GM 1 ganglioside (Figure 89.1)
accumulates in the brain and viscera [1-5]. The resultant cerebral degenerative disease is a devastating one, and affected patients usually die before two years of age. This was the first of the GM
[5], and it is the most common. It has also been referred to as type 1, but as increasing genetically determined
variation becomes evident, it is less appropriate to number these disorders. A spectrum of considerable differences in phenotype appears to reflect different degrees of residual enzyme activity resulting from different mutations. It has been practical clinically to consider GM
broadly as infantile, juvenile, or adult. Defective activity of b-galactosidase (EC 3.2.1.23)
(Figure 89.1) was first discovered by Okada and O’Brien [6]. Recognition of the enzyme abnormality led to the elucidation of later onset forms of GM
Spondyloepiphyseal dysplasia and normal intelligence in a Morquio-like syndrome were also found in patients with deficiency of the same b-galactosidase enzyme [10-12]
The multienzyme complex with cathepsin A includes b-galactosidase and N-acetylaminogalacto-6-sulfatesulfatase and sialidase. The genes are, respectively, NEU1; cathepsin A and PPGB; and GLB. Mutations in any of these components lead to functional deficiency and severe lysosomal storage disease [13]. GM
Morquio type B have an incidence of about 1:100,0001:200,000 live births [14].
