Background: Non-islet cell tumour hypoglycaemia is a rare paraneoplastic phenomenon associated with tumours secreting IGF-2 (termed IGF-2-oma). The recommended confirmatory test is the measurement of serum IGF-2: IGF-1 ratio, looking for normal to elevated IGF-2 and low IGF-1.
Clinical Case: A 51-year old woman presented with severe hypoglycaemia (glucose 1.6 mmol/L) with a six month history of episodic confusion, fatigue and altered level of consciousness. She had clubbing, arthalgia and wrist swelling consistent with hypertrophic pulmonary osteoarthropathy.
Biochemistry showed non-insulin mediated hypoglycaemia with a plasma glucose of 1.6 mmol/L, a suppressed insulin level 0.1 mU/L (2.0 – 23), C-peptide < 0.1 nmol/L (0.3 – 1.4), proinsulin <3.1 pmol/L (<13.3) and low normal IGF-1 8.1 (7.2 – 31). CT chest identified a 17.8 cm right hemithoracic mass. There were no Australian pathology sites identified to measure serum IGF-2.
She was successfully bridged with intravenous dextrose and 25mg daily prednisone prior to resection of a 2kg right solitary fibrous tumour. Immunohistochemistry staining for IGF-2 was strongly positive in keeping with an IGF-2-oma causing recurrent hypoglycaemia.
Non-islet cell tumor hypoglycemia is usually associated with large mesenchymal tumors that secrete excessive mature and incompletely processed forms of IGF-2. Abnormal IGF-2 exerts potent insulin-like activity contributing to hypoglycaemia. Within the literature, a review of 800 cases of solitary fibrous tumours documented a 5% rate of hypoglycaemia (1). The tumours are often found to be large in size; on average 20 cm in greatest dimension. Solitary fibrous tumours can be associated with hypokalaemia, acromegaloid features and hypertrophic osteoarthropathy. Here we describe a rare paraneoplastic phenomenon and simultaneously a rare cause for hypoglycaemia.
Conclusion:
This case highlights the logistical and diagnostic challenges of hypoglycaemia associated with IGF-2 secreting tumours.