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Metabolic acidosis in an Afro-Caribbean man with hyperpigmentation
  1. D A Darko,
  2. N N Chan,
  3. A Jackson,
  4. C Peiris,
  5. D O'Shea
  1. Department of Diabetes and Endocrinology, Charing Cross Hospital, Fulham Palace Road, London W6 8RF, UK
  1. Dr Darko (e-mail: d.darko{at}ic.ac.uk)

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Answers on p 439.

A 46 year old Afro-Caribbean man presented with a 10 day history of increasing malaise, polydipsia, polyuria, and weight loss. One day before admission he had become increasingly unwell and had repeated vomiting without abdominal pain. He regularly drank six units of alcohol daily (42 units per week) and had consumed three pints of beer on the day of admission. There was no previous history of diabetes, pancreatitis, or renal disease. His mother had developed type 2 diabetes in her 30s, but no other family members were known to have diabetes or any endocrine diseases.

On examination, he was dehydrated, afebrile, mildly disorientated (Glasgow coma score 14/15), and had no stigmata of chronic liver disease. Kussmaul's type respiration and ketotic breath were evident. He was obese (body mass index 35 kg/m2) with skin hyperpigmentation in the distribution of the nape of his neck, axillae (fig 1), and extensor surfaces. He was tachycardic with a pulse rate of 100 beats/min, and his blood pressure was 130/90 mm Hg on standing and 110/80 mm Hg sitting. Abdominal examination was unremarkable.

Figure 1

Hyperpigmentation in the axilla.

Biochemical investigations showed 3+ ketonuria on urine dipstick, arterial pH was 7.04, standard bicarbonate 4.0 mmol/l, carbon dioxide tension 1.89 kPa, and oxygen tension 20.0 kPa with a plasma glucose of 70 mmol/l. Serum sodium concentration was 134 mmol/l, potassium 3.6 mmol/l, urea 21 mmol/l, creatinine 196 μmol/l, and calculated plasma osmolality was 374.6 mOsm/kg (normal range 278–305). His serum amylase was raised at 184 mU/l (normal range <100). Other investigations including full blood count, liver function tests, a chest radiograph, and an electrocardiogram were all normal. Septic screen including blood and urine cultures were negative.

Questions

(1)
What is the metabolic condition in this case? Discuss the possible differential diagnosis.
(2)
What is the dermatological diagnosis (fig 1) and which endocrine/metabolic conditions is this cutaneous sign associated with?
(3)
What further investigations may be warranted in this patient?

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