Post-transplant diabetes

Editor – We read with interest the article on post-transplant diabetes mellitus.¹ Recognition of this complication of solid organ transplantation (also called new-onset diabetes after transplantation) is very important.

We wish to highlight some additional points that are important in this topic. In the context of renal transplantation, the identification of post-transplant diabetes mellitus in a patient with end stage renal disease (ESRD) of unknown cause may point to an underlying genetic diagnosis. Remarkably, the label ESRD of unknown cause is given to around 15% of all cases of renal disease requiring renal replacement therapy.² The finding of post-transplant diabetes mellitus should prompt genetic studies in the patient for mutations in HNF1B, which underlie the renal cysts and diabetes syndrome. Mutations in HNF1B lead to very variable renal phenotypes and mutations may cause ESRD of apparent unknown cause.³ A diabetes phenotype may only be revealed in cases where the pancreas is ‘stressed’, such as during pregnancy or with the commencement of steroids post transplant. Other pointers towards a diagnosis of HNF1B mutations include paediatric renal failure associated with congenital anomalies of the kidney and urinary tract, and a dominant pattern family history of phenotypes that may include renal tract anomalies, diabetes mellitus, gout, hypomagnesaemia and female genital tract anomalies.

In summary, in cases of post-transplant diabetes mellitus following kidney transplantation, physicians should review the underlying cause of the renal failure, take a full family history and have a low threshold to initiate HNF1B gene testing.

• © 2019 Royal College of Physicians