4th March 2024

A 32-year-old male presents with progressive weakness in his upper limbs

A 32-year-old male presents with progressive weakness in his upper limbs, predominantly affecting his right side. He has had bilateral shoulder weakness over the past three years, with no apparent cause identified. His father and grandmother both suffered from similar issues.

On examination today, scapular winging is noted bilaterally, worst on the right side. There is a wasting of the muscles of his arms bilaterally with relative sparing of his forearms. He is unable to lift his arms above his head. Incidentally, he has an asymmetrical smile and finds it difficult to close his eyes tightly. Reduced power is noted predominantly in the upper limbs. Power is reduced in both upper limbs but is more marked in his right upper limb. When asked to flex his neck supine, his umbilicus moves upwards.

Which of the following is the underlying diagnosis?

Select the SINGLE most appropriate option from the list below. Select ONE option only.