Systemic lupus erythematosus Quiz: Ace Your Exams

A 36-year-old woman comes to the emergency department because of chest pain and difficulty breathing that came on gradually over the past two weeks. The patient also describes feeling fatigued and feverish for the past three months. The pain is characterized as a sharp, stabbing pain in both sides of the chest that is worse with deep breathing and sneezing. The dyspnea is characterized by shortness of breath when walking across the street outside her home and is associated with a mild, non-productive cough. She denies any travel outside of the country or any sick contacts at home or work. The patient’s temperature is 37.8°C (100.0°F), pulse is 95/min, respirations are 22/min, and blood pressure is 128/78 mmHg. Physical examination reveals diminished breath sounds at both lung bases with decreased tactile fremitus. An upright chest X-ray is obtained and shows the following:    


Reproduced from: Wikimedia Commons  
Thoracentesis is performed and laboratory tests show the following:  

Laboratory value	Result	Reference range
Serum
Lactate dehydrogenase	50 U/L	45-90 U/L
Total protein	7.0 g/dL	6.0-7.8 g/dL
Amylase	50 U/L	25-125 U/L
Glucose	90 mg/dL	40-70 mg/dL
Pleural fluid
Appearance	Yellow-green, viscous	Pale yellow
pH	7.35	-
Total protein	4.5 g/dL	-
Glucose	40 mg/dL	-
Lactate dehydrogenase	80 U/L	-
Amylase	25 U/L	-
Total nucleated cells	20,000/mm3	0-1,000/mm3
Neutrophils	7%	-
Lymphocytes	80%	-
Monocytes	6%	-
Eosinophils	4%	-
Basophils	3%	-
Microbiological staining	No organisms seen on Gram or acid-fast staining	-

Which of the following is the most likely underlying etiology of this patient’s findings?