Endocrine Abstracts

18 year old male patient with GCK related monogenic diabetes. Biallelic, likely pathogenic variants identified in the GCK gene. Analysis detected two heterozygous missense variants c.693T>A p.(Asn231Lys) and c.1310C>T p.(Thr437Ile). A change on both copies of the GCK gene has been described in literature but not with this particular variant. Therefore there is a challenge in interpreting exactly what this result means. Genetic testing of both parents confirmed that one copy was inherited from each parent. GCK acts as a ‘glucose sensor’. Changes in the gene can lead to a mild increase in blood glucose and it may not require treatment. Patient diagnosed with suspected type 1 diabetes at age 4 years. He was started on insulin at diagnosis. Noted to have a very stable HbA1c between 50-60 mmol/mol and a low insulin requirement (0.2units/kg/day) delivered via insulin pump. Despite infrequent bolusing he has steady glucose levels and a time in range of 73%. He is triple antibody negative with a persisting C-peptide of 297 pmol/l. Decision against progression to hybrid closed loop therapy as unclear how patient would react to algorithm. Genetic diagnosis confirmed 8 years after diagnosis. Alternative diagnosis considered earlier but some issues with testing encountered. Family history of type 2 diabetes in Grandparents but no other family history in parents. The family have undergone genetic counselling within the genetics department. Parents have had genetics and blood glucose testing. Planned trial of reducing insulin delivered via insulin pump is ongoing, initially starting with prandial doses then background insulin. We have experienced some difficulties with patient engagement. Patient now in process of transferring to adult services. Potential for very low insulin requirement or no treatment in future. Collaboration with East of Scotland Regional Genetics Service and discussion at virtual Scottish ‘Diabetes Diagnosis Advice Clinics’. In conclusion, because the gene variants are quite unique to this patient it is difficult to predict how their diabetes will behave. This patient was initially treated as suspected type 1 diabetes but is triple antibody negative with a low insulin requirement. Currently undergoing trial of reducing insulin delivery via pump to assess response.