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Giuseppa Patti, Saverio Scianguetta, Domenico Roberti, Alberto Di Mascio, Antonio Balsamo, Milena Brugnara, Marco Cappa, Maddalena Casale, Paolo Cavarzere, Sarah Cipriani, Sabrina Corbetta, Rossella Gaudino, Lorenzo Iughetti, Lucia Martini, Flavia Napoli, Alessandro Peri, Maria Carolina Salerno, Roberto Salerno, Elena Passeri, Mohamad Maghnie, Silverio Perrotta, and Natascia Di Iorgi

Background

Autosomal dominant neurohypophyseal diabetes insipidus (adNDI) is caused by arginine vasopressin (AVP) deficiency resulting from mutations in the AVP-NPII gene encoding the AVP preprohormone.

Aim

To describe the clinical and molecular features of Italian unrelated families with central diabetes insipidus.

Patients and methods

We analyzed AVP-NPII gene in 13 families in whom diabetes insipidus appeared to be segregating.

Results

Twenty-two patients were found to carry a pathogenic AVP-NPII gene mutation. Two novel c.173 G>C (p.Cys58Ser) and c.215 C>A (p.Ala72Glu) missense mutations and additional eight different mutations previously described were identified; nine were missense and one non-sense mutation. Most mutations (eight out of ten) occurred in the region encoding for the NPII moiety; two mutations were detected in exon 1. No mutations were found in exon 3. Median age of onset was 32.5 months with a variability within the same mutation (3 to 360 months). No clear genotype–phenotype correlation has been observed, except for the c.55 G>A (p.Ala19Thr) mutation, which led to a later onset of disease (median age 120 months). Brain magnetic resonance imaging (MRI) revealed the absence of posterior pituitary hyperintensity in 8 out of 15 subjects, hypointense signal in 4 and normal signal in 2. Follow-up MRI showed the disappearance of the posterior pituitary hyperintensity after 6 years in one case.

Conclusion

adNDI is a progressive disease with a variable age of onset. Molecular diagnosis and counseling should be provided to avoid unnecessary investigations and to ensure an early and adequate treatment.

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Riccardo Bonfanti, Dario Iafusco, Ivana Rabbone, Giacomo Diedenhofen, Carla Bizzarri, Patrizia Ippolita Patera, Petra Reistadler, Francesco Costantino, Valeria Calcaterra, Lorenzo Iughetti, Silvia Savastio, Anna Favia, Francesca Cardella, Donatella Lopresti, Ylenia Girtler, Sarah Rabbiosi, Giuseppe D'Annunzio, Angela Zanfardino, Alessia Piscopo, Francesca Casaburo, Letizia Pintomalli, Lucia Russo, Valeria Grasso, Nicola Minuto, Mafalda Mucciolo, Antonio Novelli, Antonella Marucci, Barbara Piccini, Sonia Toni, Francesca Silvestri, Paola Carrera, Andrea Rigamonti, Giulio Frontino, Michela Trada, Davide Tinti, Maurizio Delvecchio, Novella Rapini, Riccardo Schiaffini, Corrado Mammì, and Fabrizio Barbetti

Objective: Transient neonatal diabetes mellitus (TNDM) is caused by activating mutations in ABCC8 and KCNJ11 genes (KATP/TNDM) or by chromosome 6q24 abnormalities (6q24/TNDM). We wanted to assess whether these different genetic aetiologies result in distinct clinical features.

Design: Retrospective analysis of the Italian data set of patients with TNDM.

Methods: Clinical features and treatment of 22 KATP/ TNDM patients and 12 6q24/TNDM patients were compared.

Results: Fourteen KATP/TNDM probands had a carrier parent with abnormal glucose values, four patients with 6q24 showed macroglossia and/or umbilical hernia. Median age at diabetes onset and birth weight were lower in patients with 6q24 (1 week; -2.27 SD) than those with KATP mutations (4.0 weeks; -1.04 SD) (p=0.009 and p=0.007, respectively). Median time to remission was longer in KATP/TNDM than 6q24/TNDM (21.5 vs 12 weeks) (p=0.002). Two KATP/TNDM patients entered diabetes remission without pharmacological therapy. A proband with the ABCC8/L225P variant previously associated with permanent neonatal diabetes entered 7-year long remission after 1 year of sulfonylurea therapy. Seven diabetic individuals with KATP mutations were successfully treated with sulfonylurea monotherapy; four cases with relapsing 6q24/TNDM were treated with insulin, metformin or combination therapy.

Conclusions: If TNDM is suspected, KATP genes should be analyzed first with the exception of patients with macroglossia and/or umbilical hernia. Remission of diabetes without pharmacological therapy should not preclude genetic analysis. Early treatment with sulfonylurea may induce long-lasting remission of diabetes in patients with KATP mutations associated with PNDM. Adult patients carrying KATP/TNDM mutations respond favourably to sulfonylurea monotherapy.