Endocrine Abstracts

Case history: A 22-year-old woman presented with a week’s history of abdominal pain and constipation. further history revealed episodes of tachycardia during childhood but no cause at that time was identified. On examination she had a sinus tachycardia, her abdomen was mildly tender and the rest of her clinical examination was completely unremarkable, including blood pressure, and there were no clinical findings consistent with Addisonian crisis.

Investigations: Sodium was found to be 104 mmol/l. Biochemistry confirmed a diagnosis of SIADH and she was referred to endocrinology. In view of the history of abdominal pain and tachycardia, and normal synacthen test, although a rapid urine dipstick test was negative a diagnosis of acute intermittent porphyria was considered.

Treatment: Her serum sodium was monitored meticulously with careful administration of hypertonic 5% saline. Although acute porphyria was suspected she was not treated with haem arginate. Biochemical confirmation of AIP was made some days after the acute episode She was discharged 8 days after admission with a normal serum sodium and a list of safe drugs to avoid further episodes. A precipitating cause for the acute episode was not identified. A genetic confirmation of AIP was also made (c.912G>C, p(Gln304His) in hydroxylmethyl bilane synthase gene. She is undergoing follow up the National Porphyria Clinic.

Conclusion: Acute intermittent porphyria (AIP) is a very rare disease which can present with hyponatraemia and a wide range of nonspecific symptoms. In view of its rarity it is not often seen apart from in MRCP questions and as clinicians we may not be confident in its management. Severe hyponatraemia can be challenging to manage and hypertonic saline needs to be given carefully in a high dependency area. We will highlight the pertinent diagnostic and management issues of both AIP and severe hyponatraemia.