Sir/Madam,

I read with interest the authors’ description of transient neonatal diabetes mellitus in a pre-term infant. Genetic studies have an important role in the management of these patients. This is an example of pharmacogenetics where the genetic cause of the insulin deficiency determines the response to treatment. It is important that mutations in the ABCC8 are looked for. In a recent case series (1), four of seven mis- sense mutations were familial. Oral sulphonylurea therapy could be effective for most patients with neonatal diabetes caused by a mutant SUR 1. Sulfonylurea therapy is also safe in the short term for patients with diabetes caused by KCNJ11 mutations and is probably more effective than insulin therapy (2). Mutations of KCNJ11 are typically associated with permanent diabetes mellitus, whereas most mutations of ABCC8 are associated with transient diabetes mellitus, perhaps reflecting a less severe form of the disease (1).

There are practical problems when dealing with insulin therapy in infancy. These include the preparation and administration of minute doses of insulin. Insulin comes in a strength of 100 units per ml. To give small doses to a baby, it is necessary to dilute this insulin to 10 units per ml. Only soluble insulin can be diluted with saline. Other forms of insulin need a specific diluent from the manufacturer on a named patient basis (personal communication). This has to be prepared in the aseptic unit and has a limited shelf life. The diluent is not licensed and is provided on a named patient basis. Home blood glucose monitoring has to be performed with a device which can cope with the neonatal haematocrit range. Dietary management would include regular feeds including night feeds and early weaning under strict dietary supervision. The multi- disciplinary team has a crucial role to play in the successful management of these infants.

1. Activating mutations in the ABCC8 Gene in neonatal

Diabetes mellitus

AP Babenko, M Polak, H Cave et al

N Engl J Med 355; 5: 456-466

2. Switching from Insulin to oral sulfonylureas in

patients with Diabetes due to Kir6.2 mutations

ER Pearson, I Flechtner, PR Njolstad et al

N Engl J Med 355; 5: 467-477