Endocrine Abstracts

A 54-year-old gentleman presented with increased urinary frequency, urgency and nocturia. His GP treated him for benign prostatic hypertrophy with tamsulosin. When this failed to alleviate his symptoms he was referred to urology. Investigations revealed he was drinking in excess of 6 litres of fluid per day, hence he was referred to endocrinology.

Aside from a 6-month history of polyuria and polydipsia, there was no history of previous head injury, headaches and no signs of any visual field defects. Investigations revealed normal fasting glucose and basal pituitary function, preserved U&Es (Na144) but high serum osmolality: 300 mosm/kg (275–295 mosm/kg) and low urine osmolality 147 mosm/kg. MRI showed appearances compatible with lymphocytic hypophysitis. A water deprivation test confirmed partial cranial diabetes insipidus (CDI). He was started on desmopressin with good effect.

Meanwhile this gentleman was being investigated elsewhere for chest pain. A CT chest revealed mediastinal, para-aortic and para-iliac lymphadenopathy. Investigations for sarcoidosis were inconclusive. Incidentally, a suspicious lesion in his left kidney and retroperitoneal fibrosis were also noted on CT. A renal biopsy performed showed evidence of interstitial nephritis. Given the host of problems this man had accumulated the question of a unifying diagnosis: immunoglobulin G4-related (IgG4-related) disease was proposed. This was confirmed with raised plasma IgG4-levels and IgG4 positive staining on renal biopsy. He subsequently developed renal failure and secondary hypogonadism. This responded well to steroid and testosterone treatment respectively. He remains on desmopressin.

Discussion: IgG4-related disease is an immune-mediated condition which can affect almost every organ system. CDI is a rare feature of this disease and even more uncommonly the presenting symptom. First reported in the literature in 2007, recent studies suggest its prevalence has been underestimated. It is therefore important to consider this multisystem disease when diagnosing CDI as this has implications on management, especially if there is multi-organ involvement.