Fig 3.

Contractures and Z disk alterations are more common MH+ biopsies. A) Contractures are sharply delimited areas where sarcomeres are greatly shortened, flanked by regions where the sarcomeres are stretched. This is a classic example from a MH+ fibre. Contractures are more frequent in MH+ than in MH- biopsies (Tables 1 and 2). B) Large area of Z line streaming in an MH+ fibre consisting of an apparent flow or extension of Z line material longitudinally towards the A band, resulting in sarcomere disarray. Z line streaming is more frequent and extensive in MH+ than MH- biopsies. C) A classical nemaline rod was found, rarely, in a single index case for a CACNA1S mutation. Other alterations are less frequently observed and not related to MH mutations. D) Dilated junctional SR with loss of CASQ content is observed in all cases. E, F) Myeloid structures are aggregations of stacked membranes with variable morphology probably due to final degradations of mitochondria, from MH- and MH+ fibres respectively. G-H Two unusual structures: “concentric laminated bodies” (F) and crystalloid inclusions in mitochondria (H) from MH- fibres. They are also rarely seen in MH+ biopsies. Bars = A, C: 2 µm; B: 1 µm. C-H: 0.5 µm.