Faculty Bibliography

Lysosomal storage disorders are a heterogeneous group of biochemical genetic disorders; currently 40-50 are known. The clinical phenotype is determined by the tissue distribution of the storage material and degree of enzyme deficiency. The genetic transmission is mostly autosomal recessive. Lysosomal storage disorders can be divided into three groups according to the major organ system pathology: (1) Primary involvement of the central nervous system without significant somatic or skeletal pathology. Disorders of grey matter, eg gangliosidosis and disorders of white matter eg the leucodystrophy are the most common; (2) Primary involvement of the reticuloendothelial system with or without associated neuropathology, eg Niemann-Pick disease and Gaucher disease; (3) Multisystem involvement in which skeletal manifestations are prominent features. The mucopolysaccharidosis and mucolipidoses are the two major forms with this clinical phenotype. Lysosomal storage disorders identified at Siriraj Hospital are neuronal ceroid lipofuscinosis, GMI gangliosidosis, mucolipidosis II, Maroteaux-Lamy, sialidosis, Sly syndrome, Hunter syndrome, Morquio syndrome, Gaucher disease, Niemann-Pick, Sandhoff disease, Pompe's disease and many more. Most patients came from the provinces where consanguinity is common. Confirmation usually is done by enzyme assays using skin fibroblast culture or leucocytes. Genetic counseling is extremely important and prenatal diagnosis is recommended to high-risk couple

Canavan disease (CD) is an autosomal-recessive leukodystrophy characterized by macrocephaly, hypotonia, and psychomotor retardation with death usually occurring in the first decade of life. It is caused by the deficiency of N-acetylaspartoacylase (ASP) which hydrolyses N-acetyl-L-aspartic acid and is most prevalent among Ashkenazim. Recently, a common mutation (A(854) --> C) in the ASP coding region has been found in 85% of Ashkenazic Jewish patients [Nature Genet 1993;5:118]. In this study we present an 18-year-old male of Creek and Ashkenazic Jewish origin with CD whose clinical features and low levels of aspartoacylase activity in fibroblasts suggested a variant form of the disease. He has had progressive spastic quadriparesis, loss of visual function, and marked volumetric reduction of cerebral and cerebellar cortex and white matter by cranial CT and MRI. Molecular analysis showed the proband as a compound heterozygote carrying in the maternal allele the A(854) --> C Ashkenazic mutation and a new mutation in the paternal allele. DNA sequencing and allele-specific oligonucleotide (ASO) analyses revealed a novel mutation, C-914 --> A, resulting in the missense Ala(305) --> Glu in the paternal Greek allele. This novel mutation may be responsible for the less severe involvement and slower progression of the disease in this patient than in classical CD

Our ongoing study of central pallidotomy for the control of Parkison's disease in selected patients has provided the opportunity to explore the topographical and somatotopic organization of the human globus pallidus. Utilizing microelectrode techniques we have obtained recordings which were correlated with data from MPTP-parkinsonian primates. In addition, we performed pre- and postoperative FDG/PET scans in these patients. Our studies reveal similarities between the MPTP-parkisonian primate model and human Parkinson's disease in terms of physiological recordings and responses. However, we have encountered significant differences between dominant and nondominant hemisphere representations, particularly for the hand, in the human. In addition, our PET studies confirmed, as in previous parkinsonian primate models, glucose hypermetabolism in the lenticular area of Parkinson's disease patients. This hypermetabolism is dramatically altered by creation of a lesion in the globus pallidus medialis. This is demonstrated by follow-up PET scans which reveal not only a decrease in metabolism of the operated lenticular region, but also in the frontal cortical projections. These combined observations of the cellular activity in globus pallidus and the observed changes in PET metabolism support the selection of the pallidum for lesioning and control of Parkinson's disease, and offer insight into the underlying physiology of this disorder. The above physiological and PET data will be clinically correlated with our ongoing series of 35+ patients

The frequency of nine different mutated alleles known to occur in the glucocerebrosidase gene was determined in 247 Gaucher patients, of whom 176 were of Jewish extraction, 2 were Jewish with one converted parent, and 69 were of non-Jewish origin. DNA was prepared from peripheral blood, active glucocerebrosidase sequences were amplified by using the PCR technique, and the mutations were identified by using the allele-specific oligonucleotide hybridization method. The N37OS mutation appeared in 69.77% of the mutated alleles in Jewish patients and in 22.86% of the mutated alleles in non-Jews. The 84GG mutation, which has not been found so far among non-Jewish patients, existed in 10.17% of the disease alleles among Jewish patients. The IVS + 1 mutation constituted 2.26% of the disease alleles among Jewish patients and 1.43% among the non-Jewish patients. RecTL, a complex allele containing four single-base-pair changes, occurred in 2.26% of the alleles in Jewish patients and was found in two (1.43%) of the patients of non-Jewish extraction. Another complex allele, designated 'RecNciI' and containing three single-point mutations, appeared in 7.8% of alleles of non-Jewish patients and in only two (0.56%) of the Jewish families. The prevalence of the L444P mutation among non-Jewish Gaucher patients was 31.43%, while its prevalence among Jewish patients was only 4.24%. The prevalence of two other point mutations--D409H and R463C--was 5.00% and 3.57%, respectively, among non-Jewish patients and was not found among the Jewish Gaucher patient population. The prevalence of the R496H mutation, found so far only among Jewish patients, was 1.13%. The results presented demonstrate that seven mutations identify 90.40% of the mutations among Jewish patients and that these seven mutations allow diagnosis of only 73.52% of the non-Jewish patients. Identification of additional mutant alleles will enhance the accuracy of carrier detection

The myelin membrane is essential for rapid conduction of nerve impulses through the central nervous system. Failure of myelination--dysmyelination--may arise through several mechanisms. The synthesis of a particular myelin protein can be defective, as occurs for proteolipid protein in Pelizaeus-Merzbacher disease and for myelin basic protein in the 18q- syndrome. Delay in myelination with a more generalized diminution in white matter is characteristic of many inherited metabolic diseases, including galactosemia, pyridoxine-dependent seizure disorder, glutaric aciduria type 1, and infantile Refsum disease. Demyelination or breakdown in myelin is characteristic of metachromatic leukodystrophy, Krabbe disease, mitochondrial disorders, adrenoleukodystrophy, Canavan disease, Alexander disease, and orthochromatic leukodystrophy. A fourth category is reserved for malformation syndromes. These include Cockayne, Fukuyama, Walker-Warburg, and Angelman syndromes. Demyelination also occurs in HIV-infected individuals with central nervous system findings and in multiple sclerosis. Much of the evidence for leukodystrophy in these disorders comes from neuroimaging. Some of these disorders are treatable