Hyperglycaemia and β-cell antibodies: Is it always pre-type 1 diabetes?

Hyperglycaemia and β-cell antibodies: Is it always pre-type 1 diabetes?

DIAB-5707; No. of Pages 3 diabetes research and clinical practice xxx (2013) xxx–xxx Contents available at Sciverse ScienceDirect Diabetes Research ...

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DIAB-5707; No. of Pages 3 diabetes research and clinical practice xxx (2013) xxx–xxx

Contents available at Sciverse ScienceDirect

Diabetes Research and Clinical Practice journ al h ome pa ge : www .elsevier.co m/lo cate/diabres

Brief report

Hyperglycaemia and b-cell antibodies: Is it always pre-type 1 diabetes? Giuseppe d’Annunzio a,*, Marta Marchi a, Concetta Aloi a, Alessandro Salina a, Francesca Lugani a,b, Renata Lorini a a b

Pediatric Clinic, IRCCS Giannina Gaslini Institute, Genoa, Italy Laboratory on Pathophysiology of Uremia, IRCCS G. Gaslini Institute, Genoa, Italy

article info

abstract

Article history:

We describe 10-year-old girl with mild incidental hyperglycaemia, impaired glucose toler-

Received 20 June 2012

ance and GADA positivity. Family history for mild hyperglycaemia and GADA fluctuation

Received in revised form

alerted us to a possible MODY diagnosis which was confirmed by detection of GCK mutation

15 November 2012

c.626C>T; p.T209M. Weak or transient b-cell autoimmunity should not preclude genetic

Accepted 3 January 2013

testing for MODY when the clinical features are suggestive. # 2013 Published by Elsevier Ireland Ltd.

Keywords: Hyperglycaemia MODY b-Cell antibodies Pre-type 1 diabetes

1.

Introduction

In type 1 diabetes mellitus (T1DM) genetic, environmental and immunological factors exert a T-cell mediated autoimmune process [1]. The immune-mediated b-cell destruction occurs over years with progressive insulin deficiency and varying degrees of hyperglycaemia ranging up to severe metabolic derangement. Immunological markers of b-cell destruction are detectable before clinical diagnosis in subjects at risk of T1DM, predict the future development of the disease and characterize the ‘‘pre-type 1 diabetes’’ condition [1]. Maturity-Onset Diabetes of the Young (MODY) is a monogenic form of non-autoimmune diabetes resulting from a primary defect of insulin secretion characterized by

autosomal dominant inheritance, genetic heterogeneity, early onset of hyperglycaemia/diabetes, presence of obesity is variable and there is a lack of insulin dependence [2]. Currently many genetic defects are known. Several studies have highlighted that MODY may be misdiagnosed as type 1 diabetes or type 2 diabetes and has potential implications in susceptibility to adulthood diabetes [3].

2.

History and examination

A 10-year-old girl was admitted for incidental hyperglycaemia. There was a family history of diabetes (mother and grandmother) and celiac disease (mother and sister). The mother had been treated with oral hypoglycaemic agents and reported

* Corresponding author at: Pediatric Clinic, University of Genoa, IRCCS G. Gaslini Institute, Largo G. Gaslini, 5, 16147 Genova, Italy. Tel.: +39 0105636528; fax: +39 0103773210. E-mail address: [email protected] (G. d’Annunzio). 0168-8227/$ – see front matter # 2013 Published by Elsevier Ireland Ltd. http://dx.doi.org/10.1016/j.diabres.2013.01.003 Please cite this article in press as: d’Annunzio G, et al. Hyperglycaemia and b-cell antibodies: Is it always pre-type 1 diabetes?. Diabetes Res Clin Pract (2013), http://dx.doi.org/10.1016/j.diabres.2013.01.003

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Fig. 1 – Electropherogram of GCK mutation c.626C>T; p.T209M in exon 6, found both in the proband and in her mother.

good metabolic control with no diabetic complications. The girl is the second child and was born at 36 weeks gestation by caesarean delivery because of gestational hypertension. Her birth weight was 2070 g and length 46 cm. The neonatal period, growth and neurological development were normal. At first evaluation she was in good general health, height 130.6 cm, weight 28.6 kg and BMI 16.9 kg/m2. Clinical history was negative for polyuria, polydipsia, and weight loss. Acanthosis nigricans was absent and eye examination was normal.

3.

Investigation

Laboratory examination revealed fasting hyperglycaemia (6.2 mmol/L) and HbA1c 6.5% (normal 4–6%). Testing for bcell auto-antibodies (GADA and IAA) was performed with 100% specificity and 100% sensitivity radioligand assay CentAK Anti-GAD65 and CentAK IAA RT (Medipan, Germany). GADA was weakly positive (1 U/mL, normal < 0.9) and IAA was negative. Oral glucose tolerance test (OGTT) showed impaired glucose tolerance (2 h plasma glucose 10.7 mmol/L). Intravenous glucose tolerance test (IVGTT) showed a First Phase Insulin Response (FPIR) of 49 mU/mL, less than 1st centile for pubertal stage [4]. Based on a slow increase in capillary glucose levels and elevated HbA1c levels, low dose insulin was prescribed (long-acting insulin analogue 0.2 U/ kg/day) which was followed by improvement of capillary glucose levels. Subsequent disappearance of GADA and stability of glycaemic levels, together with family history for mild hyperglycaemia lead us to consider a clinical diagnosis of MODY. Genetic analysis performed by direct sequencing showed a GCK mutation c.626C>T; p.T209M compatible with MODY2, also found in the patient’s mother (Fig. 1). Interestingly, GADA follow-up testing was again mildly positivity (1.7 U/mL), in the absence of signs and symptoms of metabolic decompensation.

4.

Conclusion

GCK/MODY is the most common form of MODY in Caucasians [2]. The enzymatic activity of GCK is linked with insulin secretion and GCK acts as the main glucosensor of b-cells. GCK/MODY phenotype ranges from fasting hyperglycaemia with small increases in HbA1c to mild clinical diabetes. Severe ketoacidosis and complications are extremely rare [5]. Diet

and exercise are the best initial treatment options. With more severe hyperglycemia, insulin therapy can be started followed by clinical re-evaluation. By contrast classic type 1 diabetes is preceded by a long prodromic, asymptomatic period characterized by b-cell autoimmunity and clinical diagnosis coincides with up to 90% b-cell mass destruction. Initial hyperglycaemia may evolve rapidly to severe metabolic decompensation [6]. Morbidity and mortality are still reported if the diagnosis is delayed [7], while early diagnosis positively influences partial remission and better metabolic outcomes [8]. Improvements in glycaemic control achieved initially correlate with long-term glycaemic control [9], while glycaemic instability may have negative consequences through a ‘‘metabolic memory’’ despite future improvements [10]. Incidental hyperglycaemia in children and adolescents represents a diagnostic challenge, since it can indicate a number of possibilities including pre-type 1 diabetes and monogenic forms of diabetes [11]. The search for immunological markers of b-cell autoimmunity and clinical follow-up may help for discriminate MODY from type 1 diabetes [12]. In our patient the lack of obesity and acanthosis nigricans together with hyperglycaemia and GADA positivity initially lead us to suspect a pre-type 1 diabetes. Subsequently temporary GADA disappearance, lack of progression of symptoms together with a family history of mild diabetes alerted us to the possibility of MODY. A recent survey in children and adolescents on phenotypic aspects of MODY reported a 17% prevalence of b-cell autoimmunity in genetically diagnosed MODY probands [13]. The coexistence of different form of MODY with type 1 diabetes has been reported in four cases [14–16]. Bowden described the first case, an overweight adolescent female who was firstly diagnosed as type 2 diabetes and was treated with oral agents. Worsening of metabolic control during treatment lead to suspecting type 1 diabetes, which was confirmed by positive b-cells auto-antibodies and recovery after insulin therapy. The strong family history of diabetes and the lack of acanthosis nigricans raised the suspicion of a monogenic form of diabetes and a HNF1a/MODY mutation was found. This resulted in the description of a new phenotype of ‘‘triple diabetes’’ [14]. Calcaterra et al reported the second case, a 13 years old girl with GCK/MODY diagnosed at seven years who developed clinical signs of metabolic syndrome followed by overt type 1 diabetes with b-cell autoimmunity [15]. Recently, Zucchini et al. reported worsening metabolic control in two different MODY patients (GCK/MODY and HNF1a/MODY, respectively) associated with detection of b-cell autoimmunity and insulin requiring type 1 diabetes [16]. In our case the detection of b-cells autoimmunity required us to continue careful metabolic follow-up to avoid missing severe metabolic decompensation and missing a diagnosis of type 1 diabetes. On the other hand, weak b-cells autoimmunity should not preclude genetic testing for MODY if clinical circumstances are suspicious.

Conflict of interest The authors declare that they have no conflict of interest.

Please cite this article in press as: d’Annunzio G, et al. Hyperglycaemia and b-cell antibodies: Is it always pre-type 1 diabetes?. Diabetes Res Clin Pract (2013), http://dx.doi.org/10.1016/j.diabres.2013.01.003

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Please cite this article in press as: d’Annunzio G, et al. Hyperglycaemia and b-cell antibodies: Is it always pre-type 1 diabetes?. Diabetes Res Clin Pract (2013), http://dx.doi.org/10.1016/j.diabres.2013.01.003

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