Paediatricsmiddle twist
A 9-year-old boy has two years of worsening exercise intolerance, drooping eyelids and newly fitted hearing aids. You take a family history to draw a pedigree. His mother wears a hearing aid and tires easily. Her brother developed diabetes and deafness at 32, but his three children, two of them girls, are all well. Their own mother needed a walking frame in her fifties. The boy's sister has milder hearing loss. Nobody on the father's side is affected. Which one of the following inheritance patterns does this pedigree indicate?