27th June 2023

A 5-year-old boy is reviewed in clinic with his parents, who are concerned about his difficulty walking

A 5-year-old boy is reviewed in clinic with his parents, who are concerned about his difficulty walking. The boy was sitting on the floor doing a puzzle. When asked to stand, he uses his hands on his legs to help him stand up. On examination, he has pseudohypertrophy of both calves and weakness in proximal muscles. A gene defect affecting which chromosome causes this condition?

Select the SINGLE most appropriate chromosome. Select ONE option only.