5th February 2024

A 45-year-old male presents with a 30-year history of fatigability, limiting his ability to carry out strenuous activities and sports.

A 45-year-old male presents with a 30-year history of fatigability, limiting his ability to carry out strenuous activities and sports. He manages well in his office job but has recently found himself needing help to climb up ladders and stairs to renovate his home. This is associated with muscle stiffness and pain. 

His symptoms eased off after resting and worsened if he was hungry. He did notice that he would be able to resume his work without issue once he rested for approximately 15 minutes with resolution of breathlessness, tachycardia and pain following rest. Blood tests showed raised CK levels with associated myoglobinuria. 

Which of the following enzymes are likely deficient in this condition?