Endocrine Abstracts

Introduction: B cell lymphoma of brain is a rare form of lymphoma of brain and it presetting as SIADH is very rare. In this case it was very difficult to find the cause for SIADH with all routine tests. Ultimate diagnosis was by histopathology.

Case report: 68 year old gentlemen admitted with vomiting found to be hyponatraemic with serum sodium of 122 mmol/litre. He was known to have chronic lymphocytic lymphoma treated with chemotherapy with good remission, brochiectasis and hypercholesterolaemia. His admission investigation confirmed SIADH. Than he was investigated for underlying cause for SIADH. There was no evidence of hypothyroidism, adrenal insufficiency, drugs causing SIADH. He had radiological investigation, which did not show any evidence of recurrence of chronic lymphocytic lymphoma or any other malignancy. He was treated with fluid restriction and demeclocycline initially. He had CT scan of head following fall, did not show any acute changes. Subsequently MRI scan of brain was done as he developed weakness of his right lower limb. At this point, he was complaining of headache. He had second MRI of brain which showed suspicious lesions suggestive of degenerative disease or lymphoma of brain. He developed hydrocephalous within a week and gradually deteriorated and died within 6 weeks of admission. Brain biopsy confirmed a rare form of aggressive primary B cell lymphoma of brain.

Discussion: The diagnosis of cerebral lymphoma is often delayed due to the variable presentation and rarity. It is very important to look for secondary causes SIADH, as illustrated here. It could be late effect of chemotherapy or radiotherapy of previous malignancy.

Conclusion: Although SIADH is a diagnosis of exclusion for patients presenting with hyponatraemia, it is important to establish under lying cause. SIADH is a tip of iceberg.