A 26-year-old patient complains about considerable muscle weakness, dizziness, extended abdominal pain, nausea and vomiting giving no relief. The disease has been gradually developing within 6 months. There was progress of general weakness, skin darkening. The patient fell into grave condition after an ARD: there appeared abdominal pain and frequent vomiting. Objectively: the skin is dry with diffuse pigmentation. Heart sounds are significantly weakened, heart rate - 60/min, AP- 80/40 mm Hg. The abdomen is slightly painful in the epigastrial region. In blood: WBCs - 8,1 × 109/l, glucose - 3,0 millimole/l. What is the most likely diagnosis?