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Pathological findings from left deltoid muscle biopsy at age 22 years. Groups of angular atrophic fibers (black arrows in panels a and c) are interspersed with normally sized to mildly hypertrophic muscle fibers. The slow myosin immunostaining (panel b) is roughly equivalent to ATPase at pH 4.3 and stains positive for type 1 muscle fibers (slow twitch). Type 1 muscle fibers are negative on fast myosin immunostaining (see, for example, muscle fibers 1a, 1b, 1c, and 1d in panel c). The fast myosin immunostaining (panel c) is roughly equivalent to ATPase at pH 9.4 and it stains positive for type 2 muscle fibers (fast twitch). Type 2 muscle fibers are negative on slow myosin immunostaining (see, for example, most of the angulated atrophic fibers in panel b). Widely scattered fibers are undergoing myonecrosis/myophagocytosis (white arrow in panel a).
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F1
Deltoid muscle biopsy showed marked type 1 fiber predominance and large groups of angular atrophic fibers interspersed with normal-sized muscle fibers (Fig. 1).
Forced vital capacity by age. Not plotted here are the mean inspiratory and mean expiratory pressures. At age 45 years, for example, these pressures were 26 cm H20 and 27 cm H20, respectively.
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F2
Forced vital capacity (FVC) was normal (serial testing is summarized in Fig. 2).
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