Clinical and molecular characterization of a novel INS mutation identified in patients with MODY phenotype.

Correct diagnosis of Maturity-Onset Diabetes of the Young (MODY) is based on genetic tests requiring an appropriate subject selection by clinicians. Mutations in the insulin (INS) gene rarely occur in patients with MODY. This study is aimed at determining the genetic background and clinical phenotype in patients with suspected MODY. 34 patients with suspected MODY, negative for mutations in the GCK, HNF1α, HNF4α, HNF1ß and PDX1 genes, were screened by next generation sequencing (NGS). A heterozygous INS mutation was identified in 4 members of the same family. First genetic tests performed identified two heterozygous silent nucleotide substitutions in MODY3/HNF1α gene. An ineffective attempt to suspend insulin therapy, administering repaglinide and sulphonylureas, was made. DNA was re-sequenced by NGS investigating a set of 102 genes. Genes implicated in the pathway of pancreatic ß-cells, candidate genes for type 2 diabetes mellitus and genes causative of diabetes in mice were selected. A novel heterozygous variant in human preproinsulin INS gene (c.125T > C) was found in the affected family members. The new INS mutation broadens the spectrum of possible INS phenotypes. Screening for INS mutations is warranted not only in neonatal diabetes but also in MODYx patients and in selected patients with type 1 diabetes mellitus negative for autoantibodies. Subjects with complex diseases without a specific phenotype should be studied by NGS because Sanger sequencing is ineffective and time consuming in detecting rare variants.

Continuous subcutaneous infusion of protein C concentrate using an insulin pump in a newborn with congenital protein C deficiency.

We describe the case of a newborn presenting with multicystic encephalomalacy, hydrocephalus and bilateral hemovitreous. An underlying coagulation disorder was suspected and laboratory tests revealed severe protein C deficiency. At 25 days of life, after the appearance of purpura fulminans, replacement therapy with intravenous protein C concentrate (Ceprotin; Baxter, Vienna, Austria) was started.Due to difficulties in getting peripheral venous access and to repeated loss of the venous access, continuous subcutaneous infusion of protein C was started with an insulin pump (VEO 754; Medtronic, Minneapolis, Minnesota, USA), normally adopted in patients with type 1 diabetes mellitus. Protein C values increased into the normal range and the resolution of the purpuric skin lesion was achieved. Chronic prophylaxis with low-molecular-weight heparin failed and, due to cutaneous and cerebral recrudescence, replacement therapy with the pump was started again. The insulin pump allowed us to reduce the number of injections per day and to deal with the difficulties in getting peripheral venous access, permitting medical and paramedical staff an easier management of the therapy. The dosing schedule could be easily adapted with the insulin pump and the continuous subcutaneous administration of small amounts of protein C concentrate prevented fluctuation in trough levels of protein C. This is the first reported case of a novel, successful use of an insulin pump in an extremely rare disease, to administer a drug different from insulin, which needs to be further analyzed, underlining the importance of a multidisciplinary team approach in order to provide effective and efficient care in high-complexity diseases.