Endocrine Abstracts

Introduction: In 30–50% of cases central diabetes insipidus (CDI) is idiopathic. Other causes include tumours, pituitary surgery, cranial trauma or infiltrative diseases. Long-term medical follow-up is crucial given that idiopathic CDI can be the earliest sign of an evolving process (inflammatory or tumoural).

Case report: We report the case of a 23-year-old woman who presented with isolated polydipsia and polyuria. The diagnosis of isolated CDI was established. Magnetic resonance imaging of the pituitary gland showed thickening of the pituitary stalk and loss of normal hyperintense signal of the posterior pituitary on T1-weighted images. A ¹⁸F-FDG PET/CT revealed a tumour-like lesion in the right kidney which was confirmed by a renal contrast-enhanced ultrasonography (CEUS). Granulomatous with polyangiitis (GPA) was suspected on the basis of associated maxillary sinus hypermetabolism on PET/CT and plasmatic anti-MPO ANCA positivity. Strikingly, urinalysis and renal function were normal. Furthermore sinus biopsy revealed no granulomatous inflammation. Ultrasound control performed six months later showed that the right renal mass had doubled in diameter and demonstrated new lesions in the left kidney. Renal function and urinary sediment still remained normal. Finally, US-guided biopsy of the right renal tumour revealed granulomatous inflammation consistent with the diagnosis of GPA.

Conclusions: GPA is an ANCA-associated systemic vasculitis which classically affects the upper and lower respiratory tracts and kidneys. Pituitary involvement is very rare. Renal impairment is usually characterised by glomerulonephritis with hematuria and/or proteinuria leading to progressive renal failure. Only 16 cases of GPA with renal pseudotumours have been reported. To our knowledge this is the first case combining CDI and subsequent bilateral renal tumours in the setting of GPA. This affection should be considered in the differential diagnosis of CDI. Early diagnosis and initiation of treatment could minimize the risk of irreversible pituitary function loss.