Crohn-like Disease Affecting Small Bowel Due to Monogenic SLCO2A1 Mutations: First Cases of Chronic Enteropathy Associated with SLCO2A1 Gene [CEAS] in France.

INTRODUCTION: Multiple chronic ulcers of small intestine are mainly ascribed to Crohn's disease. Among possible differential diagnoses are chronic ulcers of small bowel caused by abnormal activation of the prostaglandin pathway either in the archetypal but uncommon non-steroidal anti-inflammatory drug [NSAID]-induced enteropathy, or in rare monogenic disorders due to PLA2G4A and SLCO2A1 mutations. SLCO2A1 variants are responsible for CEAS [chronic enteropathy associated with SLCO2A1], a syndrome which was exclusively reported in patients of Asian origin. Herein, we report the case of two French female siblings, P1 and P2, with CEAS. CASE REPORT: P1 underwent iterative bowel resections [removing 1 m of small bowel in total] for recurrent strictures and perforations. Her sister P2 had a tight duodenal stricture which required partial duodenectomy. Next-generation sequencing was performed on P1's DNA and identified two compound heterozygous variants in exon 12 in SLCO2A1, which were also present in P2. CONCLUSION: CEAS can be detected within the European population and raises the question of its incidence and recognition outside Asia. Presence of intractable recurrent ulcerations of the small intestine, mimicking Crohn's disease with concentric strictures, should motivate a genetic search for SLCO2A1 mutations, particularly in the context of family history or consanguinity.

Rapid identification of HEXA mutations in Tay-Sachs patients.

Tay-Sachs disease (TSD) is a recessively inherited neurodegenerative disorder due to mutations in the HEXA gene resulting in a beta-hexosaminidase A (Hex A) deficiency. The purpose of this study was to characterize the molecular abnormalities in patients with infantile or later-onset forms of the disease. The complete sequencing of the 14 exons and flanking regions of the HEXA gene was performed with a unique technical condition in 10 unrelated TSD patients. Eleven mutations were identified, including five splice mutations, one insertion, two deletions and three single-base substitutions. Four mutations were novel: two splice mutations (IVS8+5G>A, IVS2+4delAGTA), one missense mutation in exon 6 (c.621T>G (p.D207E)) and one small deletion (c.1211-1212delTG) in exon 11 resulting in a premature stop codon at residue 429. The c.621T>G missense mutation was found in a patient presenting an infantile form. Its putative role in the pathogenesis of TSD is suspected as residue 207 is highly conserved in human, mouse and rat. Moreover, structural modelling predicted changes likely to affect substrate binding and catalytic activity of the enzyme. The time-saving procedure reported here could be useful for the characterization of Tay-Sachs-causing mutations, in particular in non-Ashkenazi patients mainly exhibiting rare mutations.

Characterization of seven novel mutations on the HEXB gene in French Sandhoff patients.

Sandhoff disease (SD) is an autosomal recessive lysosomal storage disease caused by mutations in the HEXB gene encoding the beta subunit of hexosaminidases A and B, two enzymes involved in GM2 ganglioside degradation. Eleven French Sandhoff patients with infantile or juvenile forms of the disease were completely characterized using sequencing of the HEXB gene. A specific procedure was developed to facilitate the detection of the common 5'-end 16kb deletion which was frequent (36% of the alleles) in our study. Eleven other disease-causing mutations were found, among which four have previously been reported (c.850C>T, c.793T>G, c.115del and c.800_817del). Seven mutations were completely novel and were analyzed using molecular modelling. Two deletions (c.176del and c.1058_1060del), a duplication (c.1485_1487dup) and a nonsense mutation (c.552T>G) were predicted to strongly alter the enzyme spatial organization. The splice mutation c.558+5G>A affecting the intron 4 consensus splice site led to a skipping of exon 4 and to a truncated protein (p.191X). Two missense mutations were found among the patients studied. The c.448A>C mutation was probably a severe mutation as it was present in association with the known c.793T>G in an infantile form of Sandhoff disease and as it significantly modified the N-terminal domain structure of the protein. The c.171G>C mutation resulting in a p.W57C amino acid substitution in the N-terminal region is probably less drastic than the other abnormalities as it was present in a juvenile patient in association with the c.176del. Finally, this study reports a rapid detection of the Sandhoff disease-causing alleles facilitating genetic counselling and prenatal diagnosis in at-risk families.