Most grandparents provide direct support to the sick grandchild [14]: Without the cell phone I get there with toys, I have to have time to play because otherwise he gets fed up... I sing, read a book, some childhood songs, I dance, and he laughs! (G., maternal grandmother of a 7-year-old child with centronuclear myopathy due to myotubularin 1 deficiency). Here, MTM1 is linked to autosomal dominant centronuclear myopathy.