Mitchell-Riley Syndrome: Improving Clinical Outcomes and Searching for Functional Impact of RFX-6 Mutations

AIMS/HYPOTHESIS

Caused by biallelic mutations of the gene encoding the transcription factor RFX6, the rare Mitchell-Riley syndrome (MRS) comprises neonatal diabetes, pancreatic hypoplasia, gallbladder agenesis or hypoplasia, duodenal atresia, and severe chronic diarrhea. So far, sixteen cases have been reported, all with a poor prognosis. This study discusses the multidisciplinary intensive clinical management of 4 new cases of MRS that survived over the first 2 years of life. Moreover, it demonstrates how the mutations impair the RFX6 function.

METHODS

Clinical records were analyzed and described in detail. The functional impact of two RFX6^R181W and RFX6^V506G variants was assessed by measuring their ability to transactivate insulin transcription and genes that encode the L-type calcium channels required for normal pancreatic beta-cell function.

RESULTS

All four patients were small for gestational age (SGA) and prenatally diagnosed with duodenal atresia. They presented with neonatal diabetes early in life and were treated with intravenous insulin therapy before switching to subcutaneous insulin pump therapy. All patients faced recurrent hypoglycemic episodes, exacerbated when parenteral nutrition (PN) was disconnected. A sensor-augmented insulin pump therapy with a predictive low-glucose suspension system was installed with good results. One patient had a homozygous c.1517T>G (p.Val506Gly) mutation, two patients had a homozygous p.Arg181Trp mutation, and one patient presented with new compound heterozygosity. The RFX6^V506G and RFX6^R181W mutations failed to transactivate the expression of insulin and genes that encode L-type calcium channel subunits required for normal pancreatic beta-cell function.

CONCLUSIONS/INTERPRETATION

Multidisciplinary and intensive disease management improved the clinical outcomes in four patients with MRS, including adjustment of parenteral/oral nutrition progression and advanced diabetes technologies. A better understanding of RFX6 function, in both intestine and pancreas cells, may break ground in new therapies, particularly regarding the use of drugs that modulate the enteroendocrine system.

[Occurrence of severe cardiac alterations in Amanita proxima poisoning: two original observations]

Amanita proxima is one species of white mushroom which can induce poisonings called in France "proximien" syndrome. The clinical feature of "proximien" syndrome is mainly characterized by early digestive troubles, mild hepatic cytolysis and late renal impairment. A cardiac insult has never been reported in such a circumstance. The authors describe herein two cases of white mushroom poisoning occurred in the Mediterranean French coast with a typical clinical feature of "proximien" syndrome plus secondary development of severe cardiac alterations. The outcome was good for the two patients thanks to symptomatic treatment. The cases reported here suggest that A. proxima have a potential severe cardiac toxicity leading to include early and precise cardiac examination in the management of patients poisoned by these mushrooms.

Comparison of PPCPs removal on a parallel-operated MBR and AS system and evaluation of effluent post-treatment on vertical flow reed beds

The presence in the aquatic environment of xenobiotics such as Pharmaceutical and Personal Care Products (PPCPs) has emerged as an issue of concern. Upgrading sewage treatment quality with modern technologies such as Membrane Bioreactors (MBRs) and/or implementing a further posttreatment might mitigate the release of xenobiotics into surface waters. The performance of two processes treating municipal sewage, a MBR and an Activated Sludge (AS) unit, have been compared in terms of PPCPs removal. Moreover, their effluents were treated using vertical flow reed beds. Both systems were operated under similar conditions, more specifically Hydraulic Retention Time (HRT), maintained at 8 hours, and Sludge Retention Time (SRT) set at 6 and 20 days. Pharmaceuticals belong to therapeutic groups such as antiepileptics (carbamazepine) and analgesics (ibuprofen, naproxen, diclofenac), whereas the personal care products are musk fragrances (galaxolide and tonalide). Xenobiotics removals achieved in the MBR showed better results, particularly for the acidic drugs ibuprofen (87% vs. 50%) and naproxen (56% vs. 6%) operating at low SRT. After filtration through vertical flow reed-beds, PPCPs content in effluents was decreased, below 1 ppb in most cases, improving the effluent quality and confirming reed-beds as an interesting low cost alternative in order to attenuate xenobiotics contamination.