{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,18]],"date-time":"2026-06-18T10:57:04Z","timestamp":1781780224729,"version":"3.54.5"},"reference-count":14,"publisher":"BMJ","issue":"6","content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Case Rep"],"accepted":{"date-parts":[[2026,6,1]]},"published-print":{"date-parts":[[2026,6]]},"abstract":"<jats:p>\n                    Autoimmune small-vessel cerebral vasculitis is an uncommon but potentially reversible cause of rapidly progressive cognitive and neurological decline. Its presentation can be heterogeneous, often mimicking vascular, infectious or degenerative processes. Hyponatraemia due to the syndrome of inappropriate antidiuretic hormone secretion (SIADH) may occur as a secondary manifestation of hypothalamic involvement or systemic inflammation, compounding neurological dysfunction and complicating management. We describe a middle-aged woman who developed acute cognitive deterioration, emotional lability and gait disturbance secondary to newly diagnosed autoimmune small-vessel vasculitis with serological evidence of systemic autoimmunity, on a background of prior polyautoimmune diseases (type 1 diabetes mellitus and hypothyroidism). Despite resolution of inflammatory activity following high-dose corticosteroid therapy, profound hyponatraemia (serum sodium 110\u2013120\u2009mmol\/L) persisted despite conventional measures (fluid restriction, salt supplementation and urea) and despite improvement in inflammatory activity following immunotherapy, consistent with refractory SIADH. Initiation of tolvaptan, a selective vasopressin V\n                    <jats:sub>2<\/jats:sub>\n                    -receptor antagonist, successfully resulted in gradual and sustained correction of serum sodium levels without over-rapid correction, osmotic demyelination or hepatic toxicity. Alongside longer-term immunosuppression with steroids and cyclophosphamide, this led to stabilisation of neurological and cognitive deficits. This case highlights the complexities of managing patients with cognitive and neuropsychiatric sequelae from autoimmune small-vessel central nervous system (CNS) vasculitis and the importance of evaluation and treatment of potential organic causes of cognitive impairment. To our knowledge, there are no prior published reports describing refractory SIADH in autoimmune small-vessel CNS vasculitis requiring V\n                    <jats:sub>2<\/jats:sub>\n                    -receptor antagonism. Awareness of this disease association and this effective therapeutic option allows earlier recognition and improved patient outcomes in similar cases.\n                  <\/jats:p>","DOI":"10.1136\/bcr-2025-271031","type":"journal-article","created":{"date-parts":[[2026,6,18]],"date-time":"2026-06-18T10:40:13Z","timestamp":1781779213000},"page":"e271031","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":0,"title":["Autoimmune small-vessel cerebral vasculitis with refractory SIADH: clinical recovery after V\n                    <sub>2<\/sub>\n                    -receptor antagonism (tolvaptan)"],"prefix":"10.1136","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6421-8074","authenticated-orcid":false,"given":"Fangzhi (Frank)","family":"Jia","sequence":"first","affiliation":[{"name":"Department of Neurology, Royal North Shore Hospital, St Leonards, New South Wales, Australia"},{"name":"The University of Sydney Faculty of Medicine and Health, Sydney, New South Wales, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chong","family":"Liang","sequence":"additional","affiliation":[{"name":"Department of Neurology, Nepean Hospital, Penrith, New South Wales, Australia"},{"name":"Department of Endocrinology, Monash Medical Centre, Clayton, Victoria, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mohammad Ruhul","family":"Amin","sequence":"additional","affiliation":[{"name":"Department of Neurology, Nepean Hospital, Penrith, New South Wales, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sameen","family":"Haque","sequence":"additional","affiliation":[{"name":"Department of Neurology, Nepean Hospital, Penrith, New South Wales, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"239","published-online":{"date-parts":[[2026,6,18]]},"reference":[{"key":"2026061803400773000_19.6.e271031.1","doi-asserted-by":"publisher","DOI":"10.1002\/art.40930"},{"key":"2026061803400773000_19.6.e271031.2","doi-asserted-by":"publisher","DOI":"10.1016\/j.autrev.2021.103013"},{"key":"2026061803400773000_19.6.e271031.3","doi-asserted-by":"crossref","first-page":"1301","DOI":"10.1097\/CM9.0000000000003574","article-title":"Inflammatory disorders that affect the cerebral small vessels","volume":"138","author":"Han","year":"2025","journal-title":"Chin Med J 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case of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) associated with lupus erythematosus in the central nervous system","volume":"2","author":"Hara","year":"2013","journal-title":"CEN Case Rep"},{"key":"2026061803400773000_19.6.e271031.9","doi-asserted-by":"crossref","first-page":"19","DOI":"10.5049\/EBP.2020.18.1.19","article-title":"Recurrent Severe Hyponatremia in a Patient with Sj\u00f6gren\u2019s Syndrome","volume":"18","author":"Kim","year":"2020","journal-title":"Electrolyte Blood Press"},{"key":"2026061803400773000_19.6.e271031.10","doi-asserted-by":"crossref","first-page":"579436","DOI":"10.3389\/fendo.2020.579436","article-title":"Autoimmune Hypophysitis With Systemic Lupus Erythematosus: A Case Report and Literature Review","volume":"11","author":"Xiang","year":"2020","journal-title":"Front 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