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Answers on p 421.
A 62 year old retired woman was admitted to hospital with a 10 month history of pain and weakness in the muscles of both arms and legs. Her problems began with episodic weakness in both legs such that on occasions her legs gave way and she fell to the ground. She had a gradual deterioration in her muscle strength and after a fall five months before admission she became confined to bed.
Over the month before hospital admission her weakness had progressed to the extent that she was unable to lift her head off a pillow. She had also developed pain in the muscles of the arms and legs. Of note, she had no sensory, visual, speech, or swallowing disturbance. Relevant past history included epilepsy since the age of 43, hypertension, hypercholesterolaemia, and diet controlled type II diabetes mellitus.
Drug therapy was as follows: folic acid 5 mg once daily, lisinopril 5 mg once daily, aspirin 75 mg once daily, carbamazepine 200 mg twice a day, and cocodamol as required. She was a smoker of five cigarettes per day and was teetotal.
On examination she was dehydrated but apyrexic and not distressed. She had marked proximal muscle weakness and tenderness but no fasciculation. There was grade 2/5 power in neck flexion and extension. Shoulder abduction, hip flexion, and knee extension were all weak bilaterally with 3/5 power. Finger abduction, power grip, ankle dorsiflexion, and plantar flexion were all modestly weak (4/5). The other muscle groups had full power. Upper limb reflexes were present with reinforcement, lower limb reflexes being absent, and the plantar responses flexor. There was no objective sensory deficit and the remainder of the examination was normal.
Investigations at this stage included full blood profile (haemoglobin 129 g/l, leucocyte count 11.2 × 109/l), erythrocyte sedimentation rate (ESR) 120 mm/hour, urea and electrolytes (sodium 141 mmol/l, potassium 4.7 mmol/l, urea 8.3 mmol/l, creatinine 83 μmol/l), creatine kinase 533 U/l, creatine kinase MB fraction 34, electrocardiography (normal), and chest radiography (normal).
What is the differential diagnosis and the most likely diagnosis?
How would you confirm the diagnosis?
What are the associations of this condition?
How would you manage this patient?