Fabry disease is a panethnic, X-linked, inborn error of glycosphingolipid metabolism resulting from mutations in the α-galactosidase A gene (GLA) that lead to the deficient activity of the lysosomal enzyme, α-galactosidase A (α-Gal A). Affected males with no α-Gal A activity have the early-onset classic phenotype, whereas those with residual activity present with the lateronset subtype. Recently, we reported that newborn enzyme-based screening using dried blood spots (DBS) in Taiwan revealed a high incidence of newborn males who had the GLA c.936+919G→A (IVS4+919G→A) mutation. This lesion causes cryptic splicing, markedly reducing the amount of wild-type GLA mRNA, and has been found in males with the later-onset Fabry phenotype, manifesting as cardiac, renal and/or cerebrovascular disease. To more accurately determine the incidence of the IVS4+919G→A mutation, 20,063 consecutive newborns were screened by a deoxyribonucleic acid (DNA)-based assay. Of the 10,499 males, 12 (1/875) and 24 of the 9,564 females (1/399) had the mutation. On the basis of these frequencies, the previous newborn enzymebased DBS screening (cutoff: <30% of the normal mean) only identified 67% and 17% of mutation-positive males and females, respectively. The mean DBS α-Gal A activities in the mutation-positive males and females were 23% (1.54 U) and 55% (3.63 U) of normal mean male/female values, respectively. These studies confirm the high incidence of the IVS4+919G→A mutation in the Taiwanese population and indicate that its detectability by enzyme-based DBS screening is unreliable, especially in females. These studies emphasize the superiority of DNA-based newborn screening for common mutations, particularly for X-linked diseases.

Newborn screening (NBS) aims to diagnose patients with Pompe disease earlier so that timely treatment can be applied. We describe the evolution of the screening methods in Taiwan with a population in which a pseudodeficiency variant is prevalent. We review and update the outcome of NBS-identified patients and discuss the limitations of the current therapy. We also address the challenges associated with caring for the babies with diagnosed acid alpha-glucosidase deficiency but yet without significant clinical manifestations. Further modifications of the current treatment and better predictive biomarkers should be explored.

Mutations in the SLC22A5 gene, which encodes for the plasma membrane carnitine transporter OCTN2, cause primary carnitine deficiency (PCD). After our first report of OCTN2 mutations in Chinese, three more Chinese PCD patients were identified. The parents of these families were non-consanguineous and these families were unrelated. Two novel truncating mutations were found: R254X, a single-base mutation at cDNA position 981 (c.981C>T); and Y387X (c.1382T>G). Two probands, one each from Taiwan and Macau, were homozygous for R254X. The other proband from Taiwan carried both R254X and Y387X. Two additional heterozygote carriers of R254X were also identified among 250 control samples, while none was detected for Y387X. The population carrier rate for R254X would be about 1 in 125. Haplotypes of R254X alleles were examined and patients homozygous for R254X were also homozygous for the same haplotype of intragenic and microsatellites markers. Analysis of population frequencies of haplotypes revealed that the chance of 4 chromosomes having arisen as independent events was 0.016. We conclude that R254X is probably a founder mutation in Chinese. Other previously reported mutations found in the Japanese population were also screening in 250 control samples but no carrier was identified, indicating that they were either very rare or not present in Southern Chinese.

Summary:Bone marrow transplantation (BMT) has been used for a wide variety of lysosomal storage diseases with encouraging results. We report a 3-year 5-month-old girl with Niemann-Pick type C disease (NPC) who received an allogeneic BMT. The patient presented with repeated lower respiratory tract infections, hepatosplenomegaly, failure to thrive, and developmental delay. Chest computed tomography (CT) revealed diffuse interstitial lung infiltration. Bone marrow and liver biopsies revealed abundant lipid-filled foamy macrophages. Skin fibroblast sphingomyelinase assay revealed partial deficiency. The ability of her skin fibroblasts to esterify cholesterol was very low, and the cells stained brightly for free cholesterol. She received BMT from a healthy HLA-identical male sibling donor at the age of 2 year 6 months. Full engraftment was evidenced by repeated bone marrow sex chromosome studies. Regression of the hepatosplenomegaly, markedly reduced foamy macrophage infiltration in bone marrow, and decreased interstitial lung infiltration was noted 6 months after BMT. Her neurological status, however, deteriorated. Follow-up magnetic resonance image (MRI) revealed progressive, diffuse brain atrophy. We conclude that resolution occurred in the liver, spleen, bone marrow and lung following successful engraftment. Such a response is remarkable since the underlying problem involves a membrane receptor for cholesterol. This positive response might be due to replacement of the monocyte-phagocytic system or it may imply the existence of cross-correction in the NPC membrane receptor defect by BMT approach. Since BMT did not halt the neurological deterioraton, it is unlikely to be an adequate treatment for NPC.

FMR1 (Fra X Mental Retardation 1), a gene of unknown function, is responsible for an important hereditary mental retardation, the fragile X syndrome. In this study, a 22-bp enhancer (methylation sensitive element, MSE) in the FMR1 promoter was defined by DNase I footprinting assay, and the binding of this element by nuclear factor was prevented by DNA CpG methylation. A cAMP-responsive element (CRE)-like sequence and a myc-binding sequence in MSE were identified. In the transfection assay, MSE demonstrated a strong, methylation-sensitive enhancer activity. MSE could be bound by recombinant CRE-binding protein (CREB), and its activity was stimulated by CREB in a co-transfection assay. In PC12 cells, forskolin elevated MSE activity several fold, and this induction was abolished in CRE mutants. The involvement of cAMP in the expression of FMR1 should be a clue to both the function of FMR1 and the pathogenesis of fragile X syndrome.