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Answers on p 739.
An 18 year old woman presented with a two week history of polyuria, polydypsia, and accelerated weight loss. On examination she was thin, dehydrated, hypotensive (blood pressure 88/58 mm Hg), and tachycardic (pulse 130 beats/min). Random blood glucose concentration was 20.2 mmol/l and she had hyponatraemia, hyperkalaemia, and mild uraemia (consistent with diabetic ketoacidosis); however, she was not ketoacidotic (box 1). She was diagnosed as having diabetes (subsequent testing confirmed a diagnosis of type 1 diabetes mellitus) and treated with intravenous insulin and intravenous fluid. On further questioning, she admitted to a 13 month history of easy tanning, weight loss, generalised weakness, reduced appetite, and several episodes of collapse with abdominal pain.
Box 1: Investigations at presentation. Note the low sodium, high potassium, and urea consistent with diabetic ketoacidosis, but the absence of acidosis and significant ketosis (reference ranges in parentheses)
Sodium: 118 mmol/l (135–145)
Potassium: 5.2 mmol/l (3.5–5.3)
Urea: 10.9 mmol/l (2.5–7.5)
Creatinine: 87 μmol/l (50–110)
Glucose: 20.2 mmol/l
Glycated haemoglobin: 9.0% (4.6–6.2%)
Urinalysis: ketones ++
pH: 7.4 (7.36–7.44)
Arterial carbon dioxide tension: 4.99 kPa (37 mm Hg) (4.6–6.0 kPa)
Arterial oxygen tension: 12.7 kPa (95 mm Hg) (11.3–13.3 kPa)
Bicarbonate: 23.4 mmol/l (20–28)
Saturated oxygen: 97.4%
- What test may be used to confirm a diagnosis of type 1 (as opposed to type 2) diabetes mellitus?
- Given this patient's history before this admission; what other condition are the urea and electrolytes results in box 1 consistent with and how is the diagnosis confirmed?
- What may be the explanation for this profoundly unwell patient with type 1 diabetes and hyperglycaemia not to have developed diabetic ketoacidosis?
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