Patients with KCNJ11-related diabetes frequently have neuropsychological impairments compared with sibling controls.

AIMS: KCNJ11-related diabetes is the most common form of permanent neonatal diabetes and has been associated with a spectrum of neurodevelopmental problems. We compared neurodevelopmental outcomes in patients with KCNJ11 mutations and their sibling controls. METHODS: Through our Monogenic Diabetes Registry (http://monogenicdiabetes.uchicago.edu/), we evaluated 23 patients with KCNJ11 mutations with (n = 9) and without (n = 14) global developmental delay successfully treated with sulfonylurea and 20 healthy sibling controls, using a battery of targeted neuropsychological and behavioural assessments with scaled scores that are comparable across a wide range of ages. RESULTS: Patients with KCNJ11-related diabetes without global developmental delay had significant differences compared with sibling controls on a range of assessments including IQ, measures of academic achievement and executive function. KCNJ11 patients with global delay exhibited significant differences in behavioural symptoms with a tendency to avoid social contact and displayed a reduced ability to adapt to new circumstances. Parents reported more immature behaviour, gross mood swings, bizarre thoughts, other unusual and severe behaviours, and there were also significant deficits in all subdomains of daily living skills. CONCLUSIONS: This series represents the largest and most comprehensive study of neuropsychological and behavioural dysfunction of individuals with KCNJ11 diabetes and is the first to compare outcome with sibling controls. Our data demonstrate the variety of neurodevelopmental problems seen in those with KCNJ11 mutations, even in those without recognized global developmental delays. These data can be used to counsel families and guide structured neurodevelopmental assessments and treatments based on the initial genetic diagnosis in patients with neonatal diabetes.

Successful rhIGF1 treatment for over 5 years in a patient with severe insulin resistance due to homozygous insulin receptor mutation.

BACKGROUND: Congenital insulin resistance syndromes are caused by biallelic mutations within the insulin receptor gene (INSR). Recombinant human insulin-like growth factor (rhIGF1) has been used with mixed success; however, rigorous assessment of its efficacy is lacking. Here, we describe a child with a homozygous mutation in INSR successfully treated with rhIGF1 for more than 5 years. CASE REPORT: The patient presented with osmotic diabetes symptoms and was noted to have dysplastic dentition, hypertrichosis, coarse and dysmorphic facial features. Acanthosis nigricans, skin tags and rugated hyperkeratosis were also evident on the posterior neck, axilla and groin. A homozygous INSR essential splice site mutation (c.1268 + 2T > C, p.G374 fs*12) was identified, for which both parents were found to be heterozygous. The patient was treated with twice daily injections of rhIGF1 and metformin for more than 5 years with improvement in her acanthosis nigricans, hyperkeratosis and hypertrichosis. A dramatic fall in fasting insulin, HOMA-IR and HbA1c has been maintained over the entire course of treatment without adverse effects. Her linear growth velocity has remained on target for her predicted adult height. DISCUSSION: Our case demonstrates the effectiveness of rhIGF1 as an early treatment in a patient with a biallelic mutation within INSR without evidence of fluid retention, retinopathy, muscle pain, heart failure, cerebral infarcts or benign intracranial hypertension. Her case suggests rhIGF1 can and should be considered as an initial treatment option instead of as a final option in those with INSR mutations.

Phenotypic heterogeneity in monogenic diabetes: the clinical and diagnostic utility of a gene panel-based next-generation sequencing approach.

Single gene mutations that primarily affect pancreatic ß-cell function account for approximately 1-2% of all cases of diabetes. Overlapping clinical features with common forms of diabetes makes diagnosis of monogenic diabetes challenging. A genetic diagnosis often leads to significant alterations in treatment, allows better prediction of disease prognosis and progression, and has implications for family members. Currently, genetic testing for monogenic diabetes relies on selection of appropriate individual genes for analysis based on the availability of often-limited phenotypic information, decreasing the likelihood of making a genetic diagnosis. We thus developed a targeted next-generation sequencing (NGS) assay for the detection of mutations in 36 genes known to cause monogenic forms of diabetes, including transient or permanent neonatal diabetes mellitus (TNDM or PNDM), maturity-onset diabetes of the young (MODY) and rare syndromic forms of diabetes. A total of 95 patient samples were analyzed: 19 with known causal mutations and 76 with a clinically suggestive phenotype but lacking a genetic diagnosis. All previously identified mutations were detected, validating our assay. Pathogenic sequence changes were identified in 19 out of 76 (25%) patients: 7 of 32 (22%) NDM cases, and 12 of 44 (27%) MODY cases. In 2 NDM patients the causal mutation was not expected as consanguinity was not reported and there were no clinical features aside from diabetes. A 3 year old patient with NDM diagnosed at 3 months of age, who previously tested negative for INS, KCNJ11 and ABCC8 mutations, was found to carry a novel homozygous mutation in EIF2AK3 (associated with Wolcott-Rallison syndrome), a gene not previously suspected because consanguinity, delayed growth, abnormal bone development and hepatic complications had not been reported. Similarly, another infant without a history of consanguinity was found to have a homozygous GCK mutation causing PNDM at birth. This study demonstrates the effectiveness of multi-gene panel analysis in uncovering molecular diagnoses in patients with monogenic forms of diabetes.