Weakness and shortness of breath for the past month, dry cough with aggravation of shortness of breath for past 3 days. History notable for sigmoidectomy due to colon cancer. PET-CT done 3 months earlier showed no metastases nor recurrence.

Hgb 9.3 g/dL, baseline ~10 g/dL (known iron deficiency anemia). CRP 97 mg/dL, no leukocytosis.
Mentioned that he was consuming paraffin oil for constipation.

X-ray chest showed bilateral alveolar infiltrates and fine reticulations. CT chest, likewise, showed an extensive crazy paving pattern.
Extensive infectious (serology and urine) panels taken for viruses, bacteria, and fungi, as well as a rheumatoid panel. Bronchoalveolar lavage yielded 10^4 colonies (small amount) of Enterobacter cloacae complex, possibly colonizing the airways, i.e. a contaminant. Received antibiotics and steroids, and put on a nasal hi-flow device. Released after 2 weeks.

A follow-up CT chest done 1 month later showed significant regression of the lung opacities. On the subsequent follow-up CT chest done 2.5 months later, only the subpleural reticulation persisted.

A transbronchial biopsy was obtained from the right lower lobe (RLL) right after the first CT.
Histopathology:
Small fragments of bronchus and adjacent lung tissue showing chronic inflammation, fibrosis and intra-alveolar macrophages.
Immunostains: PAN-CK positive in benign epithelial cells; CD68 positive in macrophages; CMV negative.
Note: part of macrophages containing small clear vacuoles, probably lipid-laden.

The history of paraffin oil consumption, along with the biopsy findings and CT findings, the latter which dwindled down significantly after the patient ceased consuming it, all cemented the diagnosis of exogenous lipoid pneumonia, probably acute on chronic.