CASE PRESENTATION: This patients was a 64-year-old man with hypertension. He was admitted in November 2013 with a 6 days history of high fever, productive cough and dyspnea. Dry rales and wheezing were audible in lung fields on both sides. Laboratory findings were as follows: WBC 11.63×109/L, NEU% 93%, CRP 88.5 mg/dL, ALT 66 U/L, AST 93 IU/L, LDH 488 IU/L, CK 2792 IU/L, SCr 71U/L, K+ 3.41mmol/L, Na+ 134mmol/L. Arterial blood gas analysis demonstrated hypoxemia (PaO2 = 49mmHg) under the 5L/min of nasal oxygen inhalation). Chest radiography showed obvious exudation and consolidation in right lung (Fig. 1). The patient received high-flow mask oxygen support and was empirically treated with cefoperazone-sulbactam and moxifloxacin. However, his clinical condition deteriorated rapidly and had to receive invasive positive pressure ventilation and ECMO successively, while vancomycin, intravenous methylprednisolone and immunoglobulin (IVIG) were commenced. His symptoms, oxygenation and radiography were improved slowly at 8th day and was discharged at 39th day after admission. Admission blood culture, Smears and culture of the sputum and BALF, sera antibody detecting for atypical pathogens were all negative. Loop primer-mediated isothermal amplification (LAMP) for 12 common bacteria and Multiplex real-time PCR for 20 common viruses were also negative. Finally deep sequencing of BALF Prompt suspected Mycoplasma hyorhinis infection.