Keywords
neonatal diabetes mellitus - monogenic diabetes - ABCC8 - next-generation sequencing
- β cells - newborns
Neonatal/infancy onset diabetes mellitus (NDM) is a monogenic form of diabetes occurring
within 6 months from birth. NDM can be either permanent (PNDM), requiring lifelong
treatment, or transient (TNDM), when insulin administration is necessary for 3 to
6 months and the remission persists.[1] However, a significant number of patients with TNDM (∼50% of subjects) may relapse
in late childhood or adolescence with type 2 diabetes (T2DM). NDM was considered extremely
rare with an incidence of 1:400,000 to 1:500,000 live births,[2] when it was defined as persistent hyperglycemia developing in the first 6 weeks
of life in patients born at term and treated with insulin for at least 2 weeks. However,
considering the new limit of 6 months of age the estimated incidence is 1/90,000 to
1/210,000 newborns.[1]
[3] TNDM comprises ∼50% of children with neonatal diabetes;[4] a genetic diagnosis is made in up to 90% of these patients. The majority of cases
(∼70%) result from abnormalities of the imprinted region on chromosome 6q24, such
as paternal uniparental isodisomy, paternally inherited duplication, or a methylation
defect, leading to overexpression of paternally expressed genes.[5] Most patients have intrauterine growth retardation at birth and failure to thrive.
Other features noted in the neonatal period are macroglossia and umbilical hernia.[6] Activating mutations in genes encoding the Kir6.2 (KCNJ11) and SUR1 (ABCC8) subunits
of the pancreatic adenosine triphosphate (ATP)-sensitive K+ (K-ATP) channel account
for 12% and 13% of cases of TNDM, respectively.[7] We report the case of a preterm infant with TNDM due to a ABCC8 mutation.
Case Presentation
A white male was born at 30 weeks and 4 days of gestation by emergency cesarean section
because of acute fetal distress and intrauterine growth retardation. The APGAR scores
were 8 and 9 at 1 and 5 minutes, respectively. Birth weight was 1,065 g (10th percentile),
length was 37 cm (11th percentile), and head circumference was 26 cm (6th percentile).
He was the third baby born to nonconsanguineous parents. The infant's mother had gestational
diabetes mellitus (GDM) requiring insulin treatment, resulting in good metabolic control.
No family history of diabetes mellitus was referred. Physical examination at birth
revealed no anomalies. In the second day of life, after a regular postnatal adaptation,
our patients developed hyperglycemia, with glycemia varying from 170 to 351 mg/dL,
in absence of any stress, while the infant was receiving expressed breast milk in
addition to parenteral nutrition, for a total glucose intake of 4.5 mg/kg/min. Full
septic workup, including blood cultures, C-reactive protein (CRP), and urine culture,
resulted negative. From the 5th day of life, the infant was treated with intravenous
insulin boluses of 0.1 UI/kg (Humalog, Eli Lilly and Company, Indianapolis, IN), when
glucose level rose over 250 mg/dL, according to our protocol. On the 10th day of life,
insulin and C-peptide plasma concentrations were determined and showed low values
(1.5 mU/L [normal range, 3–17], 0.32 nmol/L [normal range, 0.37–1.49], respectively);
growth hormone was 20.1 U/mL (normal range, 0.05–4.5); thyroid hormones were normal;
islet cell antibodies (ICA), insulin autoantibodies (IAA), antityrosine phosphatase
antibodies (IA2), and antiglutamic acid decarboxylase (GADA) antibodies were negative;
and abdomen ultrasound was normal. Due to the persistent hyperglycemia, and according
to diabetologist advice, multiple daily injections (MDI) was started either in the
abdomen or buttocks with insulin lispro 0.1 IU/kg/dose before meals, extemporaneously
prepared by dilution in distilled water, without any effect reproducibility. On the
14th day of life, an attempt was made to administer regular insulin at the same dose
and with the same dilution but without improvement. Furthermore, the newborn developed
lipodystrophy in the injection areas. Continuous subcutaneous insulin infusion (CSII)
was excluded because of lack of subcutaneous tissue. Considering the low weight and
very poor insulin requirement (∼0.15–0.20 UI/dose), we had to face the subsequent
challenges: (1) lack of effect reproducibility, (2) operator-dependent effect, (3)
need to use insulin syringes for injections, and (4) 8-mm syringe needles.
To overcome these obstacles, we had to plan an insulin delivery which was more reproducible
and feasible also for the parents after discharge. To provide cartridges with diluted
insulin lispro ready for use in pen injectors, we needed the Sterile Diluent ND-800
(Eli Lilly and Company,). This diluent is not authorized for commercial use in Italy
and, therefore, it was necessary to activate the procedure to import abroad registered
drugs. The following dilution was prepared by the hospital pharmacy: insulin lispro
at a 1:100 dilution (1 IU diluted = 0.01 IU insulin lispro) in sterile diluent to
yield a concentration of 1 IU/mL. A cartridge of 3 mL (297 units of sterile diluent
added to 3 UI of insulin lispro) was drawn up in the pen injector (HumaPen LUXURA
HD, Eli Lilly and Company) allowing injections with a 4-mm needle. The insulin lispro
dilution made it possible to administer accurate and exact insulin doses, thus resulting
in good glycemic control. On the 66th day of life, which was the original due date,
the infant was discharged from the hospital, with a daily insulin requirement of 0.15
UI/kg. Weight gain during neonatal intensive care unit stay was poor, with a weight
at term equivalent age of 2,076 g (0 percentile). A regular clinical follow-up was
then performed: glycated hemoglobin (HbA1c) was measured quarterly and resulted in
the normal range (< 5.8%; < 40 mmol/mol). Insulin was administered a few minutes before
each breast feed, glucose level was checked 90 minutes after meals, and the values
ranged between 100 and 150 mg/dL, while fasting hyperglycemia persisted. After discharge,
the infant's weight showed a marked catch up growth exceeding the 97th percentile.
At 2 months, corrected age hypoglycemia occurred after meals and insulin doses were
progressively decreased until suspension on the 133th day of life (2 months corrected
age) ([Fig. 1]). At the time of writing this article, the patient is ∼22 months old and is euglycemic
without insulin treatment. He is being evaluated twice a year to check glucose metabolism
since it is known that T2DM can occur around puberty in children with TNDM. Genetic
DNA testing for neonatal diabetes revealed no genetic or epigenetic aberrations at
the TNDM locus on chromosome 6q24. Therefore, next-generation sequencing (NGS) was
performed and the mutation of c.2473C > T (p.Arg825Trp) in the ABCC8 gene was identified. The mutation was inherited from the mother and is associated
to neonatal diabetes[4] ([Fig. 2]). Genomic DNA extracted from peripheral lymphocyte was analyzed by NGS approach
through targeted resequencing (454 FLX Roche platform) for a set of 182 genes. The
sequencing array targets all coding exons and flanking sequences of all 14 known MODY
genes, which were identified from genome-wide linkage study or genome-wide association
studies (GWAS) as increasing the risk of T2DM and causing diabetes in animal models.
All identified genetic variants entered a systematic data analysis pipeline that included
Sanger sequencing validation, segregation analysis, and a bioinformatic prediction
of pathogenicity.
Fig. 1 Insulin need and weight timeline.
Fig. 2 ABCC8 Sanger sequencing in the proband and parents.
Discussion
Management of neonatal hyperglycemia is challenging and no universal guidelines are
available. Stabilizing glucose levels and minimizing the hypoglycemic risk can be
difficult and the initial approach is usually represented by intravenous insulin infusion.[7] No insulin regimen, such as intermediate acting insulin, long-acting and short-acting
insulin, or rapid-acting insulin analogue, has been demonstrated to be more effective
than another. The need for tiny insulin doses and small body surface area with poor
subcutaneous tissue represent limitations in preterm infants to the use of subcutaneous
injections with pen injectors and syringes. Furthermore, breastfeeding is associated
with intraindividual variation, requiring a very flexible insulin therapy and making
it very difficult to establish the timing of insulin administration and the adequate
insulin dose by carbohydrate counting. Moreover, repeated injections can lead to the
development of lipodystrophy and to an erratic and unreliable insulin absorption,
increasing the hypoglycemic risk in these patients who are already prone to hypoglycemia.
CSII is considered safe and effective in obtaining adequate glycemic control in NDM
and offers the possibility of precise dose titration and delivery of tiny insulin
volumes.[8]
[9]
In this study, we report the case of a preterm infant with TNDM due to a ABCC8 mutation inherited from the mother who experienced insulin-treated GDM. After delivery,
the mother presented normal glucose metabolism, in particular, normal oral glucose
tolerance test (OGTT) and HbA1c. ABCC8 mutations are associated with TNDM or PNDM, but more frequently are responsible for
TNDM. The majority of ABCC8 mutations are de novo; however, dominant and recessive
inheritance occurs as well.[4] The ABCC8 mutation leads to overactivation of K-ATP channels and impairment of insulin secretion
from pancreatic β cells by increasing the magnesium-nucleotide-dependent stimulatory
action of SUR1 on the Kir pore.[10] Patients with activating mutations of the K-ATP channel genes and PND, after initial
insulin therapy, can be switched to sulfonylurea.
In our case, aforementioned clinical characteristics of our patients precluded the
possibility of treating him with CSII, and moved us to use insulin lispro at a 1:100
dilution in sterile diluent. To our knowledge, this is the first patient successfully
treated with a specifically prepared insulin dilution for pen injector instead of
syringes with distilled water. The stabilization of glucose levels resulted in good
weight gain and normal glucose metabolism without insulin and shows adequate growth
and neurodevelopment. This case report sheds light on the importance of a multidisciplinary
approach to complex cases: in this particular case, the neonatologist, the pediatric
diabetologist, the pharmacist, the dietician, and the drug company were involved and
cooperated to ensure our patient's therapeutic success.
