A 69-Year-Old Female with Tiredness and a Persistent Tan

A 69-year-old female presented with palpitations and a history of tiredness and shortness of breath for several weeks. She had a previous history of Raynaud syndrome. She was an ex-smoker. She commented that she had not lost her tan since the previous summer. Her only medication was nifedipine for her Raynaud syndrome. On examination, she was slim and tanned. Pulse rate was 86 beats per minute and regular. Her blood pressure (BP) was 105/74 mm Hg. Her chest was hyperinfl ated. The rest of her examination was recorded as normal. A chest X ray showed no evidence of cardiac failure. Electrocardiogram monitoring showed episodes of atrial fi brillation. Her routine biochemistry was as follows: serum sodium, 132 mmol/l (normal range, 135–145 mmol/l); potassium, 5.1 mmol/l (3.4–5 mmmol/l); urea, 8.6 mmol/l (2.5–6.4 mmol/l); and creatinine, 110 mmol/l (65–120 µmol/l). She was commenced on digoxin and warfarin. Her breathlessness gradually improved, and she remained in sinus rhythm. Hyponatraemia is a common electrolyte abnormality in hospitalised patients [1]. The cause is often obvious (e.g., a clear history of fl uid and electrolyte loss through vomiting or diarrhoea, or through use of thiazides or loop diuretics). A patient with hyponatraemia should be assessed by fi rst taking a thorough history, focusing on gastrointestinal symptoms, fl uid intake, thirst, postural dizziness, and medication. Evidence of intravascular volume depletion should be sought by examining skin turgour, the tongue, jugular venous pressure, and pulse rate, and most importantly, by measuring the BP in the supine and erect positions. A drop of BP by more than 20 mm Hg is indicative of intravascular volume depletion. Measurement of urinary sodium is the single most useful test. A urinary sodium concentration less than 20 mmol/l is indicative of volume depletion due to extrarenal causes (except in certain oedematous states). A urinary sodium concentration greater than 40 mmol/l suggests syndrome of inappropriate ADH secretion (SIADH), or a salt-losing nephropathy (diuretics, primary renal tubular diseases, or adrenal failure). The diagnosis of SIADH requires demonstration of normal thyroid and adrenocortical function, in the absence of intravascular volume depletion [2]. Progress The patient was admitted into hospital two weeks after the initial presentation. Her main complaints were increasing lethargy and tiredness, reduced appetite, an episode of fainting, and weight loss. On examination, she was pigmented and thin (Figures 1 and 2). Her pulse rate was 76 beats per minute in sinus rhythm. BP was …