Summaries: The common presentation is acute development of quadriplegia in patients treated with high dose steroid and neuromuscular blocker such as veruoconium. Recovery is usually complete. Histologically, there is extensive atrophy, change in staining characteristics of fibers, and electron microscopy shows characteristic loss of thick filaments. Type 2 fibers are predominantly affected.

Clinical: Also known as intensive care unit myopathy. The common presentation is acute development of quadriplegia in patients treated with high dose steroid and neuromuscular blocker such as veruoconium, one of the most common setting is treatment of patients with status asthmaticus with steroid and neuromuscular blocker. Recovery is usually complete although the aged and malnourished patients may not be successfully weaned from respirator.

HISTOPATHOLOGY AND IMMUNOHISTOCHEMISTRY: Head

Atrophy: There is extensive atrophy; type 2 fibers are more affected. A few necrotic fibers may be present.

Change in staining characteristics: Many fibers stain kind of blue with HE. Fibers also stain purple on modified trichrome, probably resulted from an excess of Z discs and a paucity of thick myofilaments.

Histochemistry:

· ATPase shows marked zones of pallor in the abnormal fibers; the center or the whole fiber may be involved.

· Oxidative enzyme reaction: diffuse light blue staining in the abnormal zone.

· Lipid: Excess lipid droplets may be present.

EM: There is characteristic loss of thick filament (i.e., selective loss of myosin). Degree of fiber loss is variable among different fibers.

REFERENCES:

Takao Mitsui, Yoshifumi Umaki, Masakazu Nagasawa, et al. Mitochondrial damage in patients with long-term corticosteroid therapy: development of oculoskeletal symptoms similar to mitochondrial disease. Acta Neuropathol (2002) 104: 260-266

Matsubara S, Okada T, Yoshida M. Mitochondrial changes in acute myopathy after treatment of respiratory failure with mechanical ventilation (acute relaxant-steroid myopathy). Acta Neuropathol (Berl). 1994;88(5):475-8. Review.