A 51-year-old woman, nonsmoker, without underlying diseases, no suspicious case history was admitted to the hospital for further workup of symptoms of cough, expectoration, and progressive dyspnea. Chest radiograph and HRCT thorax a month ago revealed increased lung markings associated with areas of bilateral and patchy ground glass shadowing. A poor response to short-term broad-spectrum antibiotic was manifested. Only one month leading up to her hospital admission again, she became virtually incapacitated by shortness of breath and exercise tolerance decreased to several feet walk at one time.
Blood pressure was 113/69 mmHg, heart rate 119 beats/min, respiration rate >30 breaths/min, oxygen saturation of 93% with high flow oxygen (10 L/min) via nasal cannula at rest, and she was about to desaturate to 88% after minimal exertion. Temperature was normal. Physical examination findings revealed a distinct respiratory distress, positive three depressions sign, and cyanopathy. Pulmonary examination findings showed remarkably decreased breath sounds and diffused velcro rale. No crackles or wheezing were appreciated. Cardiac examination revealed regular rhythm, no gallop, or edema. There was no skin rash, joint deformity, hepatosplenomegaly, or lymphadenopathy.
Blood gas analysis revealed Po2 8.54 KPa, Pco2 4.9 KPa, pH 7.421, FiO2/PaO2 = 120. WBCs and HGB were within normal limits. NEU% of 74.1% was slightly increased. Serologic examinations including ANA, Sm, UI-NRnp, Jo-1, Scl-70, SSA, SSB, P-ANCA, RF, C-ANCA, and HIV were all negative. ECG demonstrated sinus tachycardia. Chest radiography was performed which is shown in Figure 1. Her chest CT scan (Figure 2) revealed areas of ground glass attenuation and consolidation in bilateral bases of her lungs accompanied with traction bronchiectasis.
Bronchoscopy was performed and the results suggested absence of microorganism infection or tumor cell and eosinophil count was normal. Cytology and culture results for mycobacterium, fungus, and bacteria were all negative. BAL fluid test results for cytomegalovirus, chlamydia, Legionella, herpes simplex virus, and respiratory syncytial virus were negative too. Transbronchial lung biopsy (TBLB) showed slight proliferation of inflammatory and fibrous tissue. 
The patient was treated with high-concentration oxygen therapy, broad-spectrum antibiotics therapy, intravenous application of methylprednisolone (80 mg/day) in conjunction with noninvasive ventilation (Bi-PAP) which was terminated after 2 hours for man-machine counteraction. But all of the treatments were unremarkable. Dyspnea was increasingly aggravated since the 4th day after admittance to the hospital. Oxygenation index slumped to 99.9 mmHg. Based on the clinical and radiologic features she was diagnosed with AIP. Tracheotomy associated mechanical ventilation was required and methylprednisolone pulse therapy (500 mg/day, three consecutive days) was administrated. However, irreversible exacerbation of postoperative oxygenation index dropped further to 32.5 mmHg and blood pressure deteriorated as it fell to 90/60 mmHg. She eventually expired due to respiratory failure on the 7th day of admission. Percutaneous lung biopsy was performed and the slides (Figure 3) showed diffuse alveolar damage (DAD) associated with hyaline membrane formation, pulmonary interstitial edema, and immature collagen edema, and focal type II pneumocyte hyperplasia were also visible.