Coincident neuraminidase and aspartoacylase deficiency associated with chromosome 9Q paracentric inversion in a Saudi family

Neurometabolic diseases at a national referral center: five years experience at the King Faisal Specialist Hospital and Research Centre

Of 910 children under the age of 12 years referred to the national center, we were able to assign an etiology to 473 (52%). This group consisted of lysosomal storage diseases (32%), amino acid disorders (14%), organic acid disorders (16%), various chromosome abnormalities and syndromes with dysmorphia or brain dysgenesis (26%), and various other metabolic diseases (12%). While such amino acidemias as branched-chain amino acidemia (MSUD) in classic and intermediate forms (44%) and hyperphenylalaninemia (PKU) due to 6-pyruvoyltetrahydropterin synthase deficiency (6PTSD) (19%) were common, classic PKU was rare (16%). Methylmalonic acidemia (31%), 3-hydroxy-3-methylglutaryl-coenzyme A lyase deficiency (16%), and propionic acidemia (12%) were encountered more frequently than other types of organic acidemias. When compared to the number of referred Down's syndrome patients, the results suggested the birth of at least one infant with neurometabolic disease per 50 births. Five tribes of Saudi Arabia constituted 26% of the diagnosable neurometabolic diseases. Diseases such as MSUD, 6 PTSD, Sanfilippo syndrome type B, methylmalonic acidemia, homocystinuria, GM2 gangliosidosis Sandhoff variant, infantile central nervous system spongy degeneration (Canavan disease), and neuraminidase deficiency showed definite tribal occurrence. In addition, 32% to 42% of the definitely diagnosed, and 25% to 87% of patients with probable neurometabolic disease but without a definable etiology, had more than one sibling affected. It is concluded that the many rare autosomal diseases of Saudi Arabia are due to "founder effect" created by marriages occurring within tribal and extended family boundaries.

Biochemical heterogeneity of infantile central nervous system spongy degeneration

Aspartoacylase, the enzyme whose activity is deficient in infantile central nervous system spongy degeneration (Canavan-Van Bogaert-Bertrand disease), is detected as an approximately 59-kD protein in the Sephadex G-200 filtration of normal fibroblast extracts. The enzyme activity in homogenates of fibroblasts is protected by leupeptin, a protease inhibitor. In the absence of leupeptin, 90% of aspartoacylase activity is lost. In some patients with infantile spongy degeneration, no activity (less than 2%) can be detected. In some other patients with residual activity in fibroblasts, two separate peaks of enzyme are eluted with molecular weight corresponding to approximately 59 and 19 kD. Aspartoacylase activity in this latter group is protected to the same extent by the presence of leupeptin. However, the elution of two peaks is independent of the presence of leupeptin. This study indicates biochemical heterogeneity in the pathogenesis of infantile spongy degeneration.