Introduction: Mutations in the insulin receptor (INSR) gene usually progress with insulin resistance and hyperglycemia. However, rare heterozygous INSR gene mutations that cause hyperinsulinemic hypoglycemia (HH) have also been described. A case with hyperinsulinemic hypoglycemia due to a new variant mutation in the INSR gene, is presented.
Case: A 13-month-old male patient was referred to us with complaints of contractions in his entire body and low blood sugar in his history. He was born 3900 grams with spontaneous vaginal delivery as term birth. He had a similar seizure history 1 month ago. In family history; There was no consanguinity between father and mother. His father had a growth hormone treatment history and he had iris coloboma. Anthropometric measurements; Height: 78 cm (SDS: 0.24), weight: 12.1 kg (SDS: 1.08), head circumference: 45 cm (SDS: -0.37) was normal. In the physical examination of the patient, anterior fontanel was 0.5*0,5 cm open, elongated penis length was 3,5 cm, testicles were bilaterally palpable, other system examinations were normal. Laboratory values measured in hypoglycemic state (glucose: 35 mg/dL) are given in the table. In addition, the patient's metabolic tests (tandem, blood amino acid, urine organic acid, ammonia) were normal.
|Hormonal Tests:||Patient Results||Reference Ranges|
|Growth hormone||4,1||(0,10-6,20) ng/mL|
|Lactic acid||11,8||(4,5-19,8) mg/dl|
|Thyroid stimulating hormone||0,69||0,66-4,75 uIU/mL|
|Insulin like growth factor binding protein 3||3,04||0,8-3,9mg/L|
Hydrocortisone and diazoxide treatment were started simultaneously because the cortisol levels measured at the time of hypoglycemic attack were 3.9 mg /dL (low) and insulin was 7.6 uU/mL. Abdominal ultrasound was requested for the examination of pancreatic anomaly and it was found to be normal. Genetic result showed in INSR NM_000208.2 Exon 20 c.3634G>A p mutation. A new mutation was detected in Val1212lle. During the follow-up the basal cortisol value measured was 16.2 mg /dL. After this result and genetical diagnosis, hydrocortisone treatment was discontinued and diazoxide treatment was continued. The patient's blood sugar is followed closely, and the follow-up continues in terms of conversion to diabetes.
Conclusion: In conclusion, heterozygous INSR gene mutation causing hyper insulinemic hypoglycemia was detected in our case. This case is presented because INSR mutations are rare in the etiology of hyperinsulinism in hypoglycemic patients and also the detected mutation is new.
15 Sep 2022 - 17 Sep 2022