Persistent hypomagnesaemia caused by HNF1B-MODY in a patient on platinum-based chemotherapy: A case report and review

Abstract

We report a case of a 60 year-old female with persistent refractory hypomagnaesemia caused by HNF1B gene deletion. Her hypomagnaesemia had been attributed to the use of adjuvant platinum chemotherapy administered 2 years previously following a haemicolectomy for colorectal cancer. However it emerged that she had HNF1B gene deletion and had been diagnosed with MODY thirteen years previously. Her hypomagnaesemia was in fact longstanding and predated chemotherapy use. Previous abdominal imaging showed bilateral renal cysts and uterine didelphys which are consistent with anatomical features of HNF1B dysfunction. Her hypomagnaesemia is most likely related to HNF1-MODY. She continues to be managed with regular magnesium infusions and will likely require this as a lifelong measure. This case served as a reminder to look beyond medications as a potential cause for hypomagnesaemia and consider rare genetic conditions.