Myasthenia gravis is an autoimmune disorder of peripheral nervous system, leading to fluctuating muscle weakness. It is caused by circulating antibodies that block acetylcholine nicotinic postsynaptic receptors at the postsynaptic neuromuscular junction. Myasthenic crisis is a life-threatening complication, which is defined as weakness from acquired myasthenia gravis. In this paper we described a 15-year-old boy who was admitted to the Paediatric Intensive Care Unit due to myasthenic crisis. He had suffered not only from myasthenia gravis but also hypothyroidism, cerebral palsy and epilepsy. The patient required mechanical ventilation and was successfully treated with both plasmapheresis and intravenous immunoglobulins. He recovered from the crisis and then thymectomy was performed. Perioperative period and anaesthesia passed uncomplicated. Discharged home from the hospital after 2.5 month-treatment, for the last 4 years, he has only come on scheduled outpatient medical appointments. This case reveals that myasthenic crisis, albeit rare, may occur in male adolescents. In such cases multidisciplinary care followed by surgery becomes a procedure of choice. Concomitant medical problems, if well controlled, do not affect the results of outcome of the underlying disease.