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अमूर्त

Cessation of Multiple Daily Insulin Injections in a Person with Twenty-Nine Years of “Type 1 Diabetes”.

Joel LIM Guanyi, Su Fen ANG, Clara Tan SH, Jessie Fong CW and Su Chi LIM

Diabetes mellitus is a complex and etiologically heterogeneous metabolic disorder. Therefore, accurate classification of patients into diabetes-subtypes remains a challenge in clinical practice. We report a 50-year-old, non-obese (Body Mass Index (BMI) 22.4 kg/m2) Chinese lady who was diagnosed with Type 1 Diabetes Mellitus (T1DM) at age 21. This diagnosis was made owing to abnormal glucose tolerance detected during pregnancy and the young-onset nature of the disease. Subsequently, a multiple daily insulin injection (MDI) regime was initiated and maintained for almost three decades. Given a few clinical features atypical of T1DM (i.e. relatively stable fasting and post-absorptive glucose profile along with being non-ketotic prone despite occasional interruption of MDI, suggesting preserved pancreatic β cell insulin secretory function), the diagnosis was re-visited. She was subjected to deep re-sequencing of a panel of 16 candidate genes implicated in monogenic diabetes (or Maturity Onset Diabetes of the Young [MODY]) using Next Generation Sequencing (NGS) technology. A glucokinase (GCK) coding non-synonymous mutation (S441W), novel among Asians was discovered. The mutation was predicted to be functionally deleterious by multiple bioinformatics algorithms. Additionally, one recent in vitro site-directed mutagenesis study reported reduced enzyme-substrate (i.e. glucose) affinity associated with this variant. This suggested a revised diagnosis of MODY2. Notwithstanding the long-standing duration of diabetes, she was successfully weaned off from all anti-diabetic agents over the next few months with modest impact on her global glycemic profile (HbA1c 6.4% to 6.9%). Averting unnecessary long-term pharmacotherapy often means substantial health-cost savings, avoidance of potential treatment-related adverse-effects and importantly, better quality of life for the person and their family members. This case-report serves as an important reminder to reconsider the diagnosis and consider the option of genetic testing (especially in the era of NGS), among diabetic individuals with features atypical of the classic forms of diabetes.