Introduction

HNF 1B is a widely distributed transcription factor¹. The 17q12 deletion is a contiguous gene syndrome encompassing HNF 1B that accounts for an extended phenotype compared to HNF 1B mutations alone². Furthermore, previous studies of HNF 1B mutations are limited by incomplete investigation of the extra-pancreatic features¹. It is therefore unclear if the phenotypical features of HNF 1B mutations have been fully characterized. 

Case

This case describes a 28yo Caucasian woman presenting with symptomatic hypomagnesaemia on a background of T2DM on oral hypoglycaemic agents (diagnosed at 18 years old), previous pancreatitis and anaemia secondary to iron and vitamin B12 deficiency. There was no prominent family history of early onset diabetes. Examination revealed a high forehead, prominent gums and high arched eyebrows. Biochemistry showed hypomagnesaemia with associated hypermagnesuria and hypocalciuria with normal renal function. Imaging of her renal tract showed a simple cyst in the right kidney with prominence of the renal pelvis bilaterally. Neuro-imaging performed for her initial symptoms of face and arm parasthaesias with headaches revealed findings of hyperostosis frontalis interna with no intracranial abnormality. Bone Mineral Density scans revealed high bone density with a T score of +2.3 at the femoral neck and +2.5 at L2-4. She was treated with parenteral magnesium replacement. Further genetic testing confirmed a 1.4Mb deletion at chromosome 17q12 encompassing the HNF 1B gene. 

Summary

We describe a case of 17q12 deletion presenting with facial, pancreatic (endocrine and possible exocrine) and renal features including tubular defects. Renal tubular defects have only recently been described with HNF 1B mutations³. 17q12 deletion has also been shown to be associated with dysmorphic features and neuropsychiatric defects. The latter was not present in our patient. The association with hyperostosis frontalis interna or increased bone density has not previously been described.