We have identified a lethal phenotype characterized by sudden infant death (from cardiac and respiratory arrest) with dysgenesis of the testes in males [Online Mendelian Inheritance in Man (OMIM) accession no. 608800]. Twenty-one affected individuals with this autosomal recessive syndrome were ascertained in nine separate sibships among the Old Order Amish. High-density single-nucleotide polymorphism (SNP) genotyping arrays containing 11,555 single-nucleotide polymorphisms evenly distributed across the human genome were used to map the disease locus. A genome-wide autozygosity scan localized the disease gene to a 3.6-Mb interval on chromosome 6q22.1-q22.31. This interval contained 27 genes, including two testis-specific Y-like genes (TSPYL and TSPYL4) of unknown function. Sequence analysis of the TSPYL gene in affected individuals identified a homozygous frameshift mutation (457_458insG) at codon 153, resulting in truncation of translation at codon 169. Truncation leads to loss of a peptide domain with strong homology to the nucleosome assembly protein family. GFP-fusion expression constructs were constructed and illustrated loss of nuclear localization of truncated TSPYL, suggesting loss of a nuclear localization patch in addition to loss of the nucleosome assembly domain. These results shed light on the pathogenesis of a disorder of sexual differentiation and brainstem-mediated sudden death, as well as give insight into a mechanism of transcriptional regulation.

This paper summarizes the published experience as well as results of the 3rd International Workshop on Glutaryl-CoA Dehydrogenase Deficiency held in October 2003 in Heidelberg, Germany, on the topic treatment of patients with glutaryl-CoA dehydrogenase (GCDH) deficiency. So far no international recommendation for treatment of GCDH deficiency exists. Such an approach is hampered by several facts, namely the lack of an in-depth understanding of the pathophysiology of the disease, the lack of prospective studies, including the evaluation of drug monotherapy, and lack of objective documentation of clinical changes (e.g. video documentation) during pharmacotherapy.

During the last decades, efforts have been made to elucidate the complex mechanisms underlying neuronal damage in glutaryl-CoA dehydrogenase deficiency. A combination of in vitro and in vivo investigations have facilitated the development of several hypotheses, including the probable pathogenic role of accumulating glutaric acid and 3-hydroxyglutaric acid. However, there are still many shortcomings that limit an evidence-based approach to treating this inborn error of metabolism. Major future goals should include generation of a suitable animal model for acute striatal necrosis, investigation of the formation, distribution and exact intra- and extracellular concentrations of accumulating metabolites, a deeper understanding of striatal vulnerability, and systematic investigation of effects on cerebral gene expression during development and of the modulatory role of inflammatory cytokines.

The metabolic hallmark of glutaric aciduria type I (GA I) is the deficiency of glutaryl-CoA dehydrogenase (GCDH) with subsequent accumulation of glutaric acid, 3-hydroxglutaric acid (3-OH-GA) and glutaconic acid. Current concepts regarding pathomechanisms of GA I focus on investigations of excitotoxic effects of 3-OH-GA. To identify pathogenetically relevant genes, microarray analyses were performed using brain material from GCDH-deficient (GCDH (-/-)) and control mice. These microarray data confirmed recent pathogenic models, but also revealed alterations in genes that had previously not been correlated to the disease, e.g. genes concerning vascular biology. Subsequent in vitro and in vivo experiments confirmed direct effects of 3-OH-GA on vascular permeability and endothelial integrity. Clinical observations underscore the involvement of vascular dysfunction. In MRI scans of GA I patients, subdural effusions as well as dilated transarachnoid vascular plexuses were detected independently of encephalopathic crises. In fact, some of these findings are already detectable shortly after birth. MRI scans of a GA I patient performed during an acute encephalopathic crisis detected a dilated intrastriatal vasculature with perivascular hyperintensity, indicating local extravasation. In conclusion, we hypothesize that 3-OH-GA affects prenatal development of vessels, thus leading to an increased vulnerability of endothelial structures and subsequent vascular dysfunction. These observations display an additional pathomechanism in GA I and might explain frontotemporal hypoplasia and chronic subdural effusions in this disease. Elucidation of the pathomechanisms of vascular dysfunction may give further insights into the pathogenesis of GA I.