Maturity-onset diabetes of the young (MODY) 5 is caused by mutations in the TCF2 gene encoding the transcription factor hepatocyte nuclear factor-1␤. However, in 60% of the patients with a phenotype suggesting MODY5, no point mutation is detected in TCF2. We have hypothesized that large genomic rearrangements of TCF2 that are missed by conventional screening methods may account for this observation. In 40 unrelated patients presenting with MODY5 phenotype, TCF2 was screened for mutations by sequencing. Patients without mutations were then screened for TCF2 rearrangements by the quantitative multiplex PCR of short fluorescent fragments (QMPSF). Among the 40 patients, the overall detection rate was 70%: 18 had point mutations, 9 had whole-gene deletions, and 1 had a deletion of a single exon. Similar phenotypes were observed in patients with mutations and in subjects with large deletions. These results suggest that MODY5 is more prevalent than previously reported, with one-third of the cases resulting from large deletions of TCF2. Because QMPSF is more rapid and cost effective than sequencing, we propose that patients whose phenotype is consistent with MODY5 should be screened first with the QMPSF assay. In addition, other MODY genes should be screened for large genomic rearrangements. Diabetes 54:3126 -3132, 2005 M aturity-onset diabetes of the young (MODY) is characterized by the occurrence of nonketotic diabetes of early onset, typically before the age of 25, caused by primary insulinsecretion defects and inherited as an autosomal dominant trait. Currently, heterozygous mutations in six different genes have been identified as a cause of MODY. These genes encode the enzyme glucokinase (MODY2 subtype) and the following transcription factors: hepatocyte nuclear factor-4␣ (HNF-4␣; MODY1), HNF-1␣ (TCF1; MODY3), insulin promoter factor 1 (MODY4), HNF-1␤ (TCF2; MODY5), and neurogenic differentiation factor 1 (MODY6) (1).In 20 -40% of the patients presenting with clinical and family history consistent with MODY, no mutation in the known MODY genes are found (2,3). Part of these socalled MODY-X cases may be caused by mutations in still unidentified genes. Alternatively, some MODY-X cases could result from complex molecular alterations in the known MODY genes that are missed by conventional screening methods.This hypothesis is supported by the observation that large genomic rearrangements account for up to 20% of the molecular defects responsible for other monogenic diseases (4 -7). PCR amplification of individual exons followed by sequencing is currently the standard screening method for MODY mutation analysis. However, in the case of large genomic deletions involving one or several exons, this method would yield false-negative results due to the amplification of the single wild-type allele.MODY5 encompasses a wide clinical spectrum comprising diabetes, pancreas atrophy with subclinical exocrine deficiency, progressive nondiabetic nephropathy, kidney and genital malformations, and liver test abnormalities (8). Sequence ...

Krabbe disease usually presents as a severe leukodystrophy in early infancy and childhood. From a series of 11 patients and 30 cases previously reported in the literature we describe the clinical, radiological, electrophysiological and genetic features of adult Krabbe disease. Patients diagnosed after the age of 16 years were included in this study. They were further divided into three groups depending on age at symptoms onset: (1) childhood onset cases (n = 7); (2) adolescence onset cases (n = 6) and adult onset cases (n = 28). Overall, 96 % of patients in the adult-onset group presented with signs of pyramidal tracts dysfunction. Spastic paraparesis or tetraparesis became prominent in all cases. A peripheral neuropathy was present in 59 % of cases and was most often demyelinating (80 %). Other clinical signs encompassed dysarthria (31 %), cerebellar ataxia (27 %), pes cavus (27 %), deep sensory signs (23 %), tongue atrophy (15 %), optic neuropathy (12 %), cognitive decline (12 %). Cerebrospinal fluid protein concentration was moderately increased in 54 % of patients. Patients in the adolescent- and childhood-onset groups had similar presentations but were more likely to display optic neuropathy (33 % and 57 %) and cerebellar ataxia (50 % and 57 %). In the adult-onset group, the disease progressed slowly over more than 10 years, but a rapid course was observed in two patients. Abnormalities of brain MRI was similar in the three groups and included high signals of cortico-spinal tracts (94 % of cases), hyper-intensities of optic radiations (89 %) and hyper-intensities or atrophy of the posterior part of the corpus callosum (60 %). No clear genotype-phenotype relationship could be demonstrated.

Background Adenosine kinase deficiency is a recently described defect affecting methionine metabolism with a severe clinical phenotype comprising mainly neurological and hepatic impairment and dysmorphism. Methods Clinical data of 11 additional patients from eight families with adenosine kinase deficiency were gathered through a retrospective questionnaire. Two liver biopsies of one patient were systematically evaluated. Results The main clinical symptoms are mild to severe liver dysfunction with neonatal onset, muscular hypotonia, global developmental retardation and dysmorphism (especially frontal bossing). Hepatic involvement is not a constant finding. Most patients have epilepsy and recurrent hypoglycemia due to hyperinsulinism. Major biochemical findings are intermittent hypermethioninemia, increased S-adenosylmethionine and Sadenosylhomocysteine in plasma and increased adenosine in urine. S-adenosylmethionine and S-adenosylhomocysteine are the most reliable biochemical markers. The major histological finding was pronounced microvesicular hepatic steatosis. Therapeutic trials with a methionine restricted diet indicate a potential beneficial effect on biochemical and clinical parameters in four patients and hyperinsulinism was responsive to diazoxide in two patients. Conclusion Adenosine kinase deficiency is a severe inborn error at the cross-road of methionine and adenosine metabolism that mainly causes dysmorphism, brain and liver symptoms, but also recurrent hypoglycemia.

No abstract