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An unusual case of hyponatraemia Natasha Porcu Southampton General Hospital

An unusual case of hyponatraemia Natasha Porcu Southampton General Hospital. Mrs M 30 yr old Portuguese female pc : presented in A&E (13/12/04)- abdominal pain and frequent vomiting . On examination : abdomen soft and tender, BP 162/94. Pregnancy test (+) ectopic pregnancy?

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An unusual case of hyponatraemia Natasha Porcu Southampton General Hospital

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  1. An unusual case of hyponatraemia Natasha Porcu Southampton General Hospital

  2. Mrs M • 30 yr old Portuguese female • pc: presented in A&E (13/12/04)- abdominal pain and frequent vomiting On examination: abdomen soft and tender, BP 162/94 Pregnancy test (+) ectopic pregnancy? - plasma β-HCG: 682 IU/L (500-10,000 3-4 weeks pregnant) - normal ultrasound

  3. pmh: admitted 8 months earlier with abdominal pain Gastritis? pain resolved after 2 days. dh: not on any prescribed medication sh: 10 cigarettes/day, ½bottle of wine/night regular cannabis user

  4. High blood pressure/tachycardia throughout her hospital stay TFT’s (21/12/04) Free T4= 48.9 pmol/L (11.5-24.0) TSH= <0.01 mIU/L (0.35-5.50)

  5. Abdominal pain • Gastritis, constipation, appendicitis ruled out • Porphyria? Random urine porphyrin screen (24/12/04) Porphobilinogen - detected Urine porphyrin 1800 nmol/L (0-320) Porphyrin/creatinine ratio 147.7 (0-35) Acute Intermittent Porphyria

  6. Trend in measured plasma sodium during her hospital stay

  7. Day 14: plasma Na 103 mmol/L (135-145) plasma osmolality=225 mOsmol/kg (280-295) urine osmolality= 735 mOsmol/kg urine sodium= 57 mmol/L Syndrome of inappropriate ADH secretion (SIADH)? Summary: acute porphyria, pregnant, thyrotoxic with SIADH

  8. SIADH: A diagnosis of exclusion • Criteria: • low plasma sodium and osmolality • urine sodium >20 mmol/L • urine osmolality inappropriately high (>200 mOsm/kg) • patient should be clinically euvolaemic • exclude renal, adrenal, hypopituitary and cardiac disease • exclude drugs that may affect water balance • clinical and biochemical improvement to water restriction

  9. Haem Biosynthetic Pathway Acute Intermittent Porphyria Marshall WJ, Bangert SK. Clinical Chemistry. 5th ed. 2004

  10. AIP • rare autosomal dominant disorder (1-2 cases:100,000 in UK) • build-up of neurotoxic porphyrin precursors during an acute attack • Precipitating factors: alcohol • physical/emotional stress • weight loss • hormonal changes • many drugs • -

  11. Symptoms of acute intermittent porphyria (AIP) Abdominal pain Nausea and vomiting Tachycardia Hypertension Hyponatraemia (SIADH) Psychological disturbances Muscle weakness Thyrotoxicosis? neurological

  12. Brodie et al (1978), 17 patients with AIP: 13 in remission (normal thyroid function) 4 in acute attack- had significantly elevated thyroid hormones (increase related to severity of attack) ‘‘AIP may represent a reversible cause of hyperthyroidism in man…… increased thyroidal sympathetic neural stimulation may be responsible’’ Brodie et al. Thyroid function in acute intermittent porphyria: A neurogenic cause of hyperthyroidism? Horm Metab Res 1978; 10: 327-31

  13. Recovery of Mrs M • IV haem-arginate to suppress the pathway (26/12/04) • Propanolol and propylthiouracil for thyrotoxicosis (24/12/04) Random urine sample: porphobilinogen (not detected) urine porphyrin 78 nmol/L (0-320) Free T4= 19.3 pmol/L (11.5-24.0) TSH= 0.02 mIU/L (0.35-5.50) Na = 137 mmol/L on discharge

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