Unravelling the Mysterious Weakness

Author: Prakash Palaniappan Solaiyappan / Editor: Nick Tilbury / Codes: EnC6, GP9, MHP3, NepC3, NepP1, NeuC12, NeuC5, NeuC7, NeuP8, SLO11, SLO3 / Published: 11/09/2024

A 51-year-old male attends the emergency department (ED) reporting sudden-onset chest pain and severe weakness in all four limbs. He tells you his pain score was initially 4/10 in severity but has now largely subsided. He is also experiencing nausea, vomiting, clamminess, and palpitations.  

The patient has lost 10kg in the last 12 months and has been experiencing intermittent diarrhoea. He has recently had both a colonoscopy and endoscopy, which were unremarkable.

His observations are as follows:

• Heart rate: 132/min
• Right arm blood pressure: 105/76 mmHg
• Left arm blood pressure: 99/60 mmHg
• SpO2: 97% on room air
• Respiratory rate: 19/min
• Temp: 37.6°C

On examination, he looks unwell but is fully conscious. There is no radio-radial delay or radio-femoral delay. He appears to have no power in any of his limbs. Examination is otherwise unremarkable.

A venous blood gas is done as part of the initial work-up:

• pH: 7.349
• PCO2: 5.36 kPa
• PO2: 10.2 kPa
• Sodium: 143 mmol/L
• Potassium: 1.7
• Chloride: 109 mmol/L
• Calcium (Ca): 1.30 mmol/L
• Urea: ?
• Creatinine: 68 µmol/L
• Glucose (Glu): 8.4 mmol/L
• Lactate: 1.1 mmol/L
• Haemoglobin (Hb): 154 g/L
• Base excess: -3.3
• Anion gap: 11.6
• Bicarbonate (HCO3): 21.6 mmol/L