Endocrine Abstracts

Background: Guillain-Barré syndrome is a rare but very serious autoimmune disorder and it’s caused by the immune led demyelination of the peripheral nervous system. The symptoms are mainly weakness and numbness, but can also consist in severe respiratory failure due to paralysis. The treatment consist in administration of intravenous immunoglobulins (IVIGs) which shorten the duration of disease.

Case presentation: A 67 year-old man was referred to our Endocrinology team due to hyponatremia. The patient was admitted in the hospital 6 days previously due to 1-day history of hand and legs numbness and weakness. He denied any recent history of trauma to the spine Two weeks prior to this current emergency visit, he complained of flu like symptoms and upper respiratory tract infection. On admission he was alert, and not in respiratory distress. His presenting vitals were stable. Neurological: reduced tone, muscle power of 4/5 bilateral upper and lower limbs, absent tendon reflexes at the patellas and ankles, bilateral downgoing plantar response and reduced sensation to soft touch and pin prick from knee below. The cranial nerves were intact. Examination of cardiovascular, respiratory systems, abdominal and skin were unremarkable. His full blood count, renal and liver function, cardiac enzymes, blood gas were within normal limits.

Patient received 5 days of IVIGs and then the Sodium dropped to 125 mmol/l. This was considered SiADH, started on fluid restriction and referred to Endocrinology. Seen by our team 48 h later (bank holiday) – patient was stable but worsening hyponatremia.

Initial impression: Pseudohyponatremia secondary to IVIGs (this medication is known can increase plasma Osm).

Final Diagnostic: True Hypotonic Hyponatremia as further investigations revealed low Plasma Osmolality 263 mmol/kg with significant increased Urine Osmolality (687 mmol/kg) and loss sodium in the urine. The fluid restriction was stopped and for next few days the hyponatremia actually initially worsen (lowest Na 117 mmol/l) due to a very complex mechanism. The patient received iv fluids and slow salt tablets for 3 days. The Sodium level had slowly improved and remained stable. We reviewed other cases which were previously treated with IVIG. Unfortunately the data was limited but other cases of hyponatremia post IVIGs were identified.

Conclusions: We would like to highlight our case for the need to be vigil about such complications and to avoid fluid restriction in cases of patients treated with IVIGs as this can worsen hyponatremia.