A 36-year-old female was admitted to the intensive care unit after resuscitation diagnosed with diabetic ketoacidotic coma, which was the first manifestation of her diabetes mellitus. It may have been provoked by pulmonary or gastrointestinal coinfection. Five days following admission the patient regained consciousness and homeostasis returned to normal. One week after the stabilization of her cardiopulmonary state, weaning from the respirator turned out to be unsuccessful: flaccid tetraparesis developed with rapid muscle atrophy and absence of deep tendon reflexes. The sensory system and cranial nerves remained intact. Electrophysiological studies and muscle biopsy showed serious acute illness myopathy with mild demyelination owing probably to the latent diabetes. The course of acute quadriplegia was fluctuating and correlated mainly with the activity of the systemic inflammatory response syndrome mechanisms. Myopathy might have been aggravated by using high-dose glucocorticoid therapy. The patient's general condition improved quickly as a result of full recovery from sepsis, discontinuation of glucocorticoids and normoglicaemia maintained by subcutan insulin substitution. Eight months after admission almost full neuromuscular restitution was achieved showing the reversibility of this grave illness.