Bronchoalveolar Lavage in Liquid Paraffin Pneumonitis: Discussion (2)

Since the paraffin-loaded AM have suggestive but nonspecific histochemical features, liquid paraffin must be identified by TLC of the BALF lipid extract. Liquid paraffin was identified for the seven patients as a very hydrophobic compound migrating on the front in the solvent systems used for phospholipid or neutral lipid separation. This abnormal compound was faintly stained by iodine vapor and was identified as liquid paraffin by comparison with medicinal liquid paraffin deposited on the same plate. Furthermore, since cholesterol ester and paraffin spots were not completely separated in the solvent system for neutral lipid, the resolution was further improved by replacing this solvent system by pure hexane when the solvent front reached the three fourths of the plate. Therefore, cholesterol ester spot did not move anymore, whereas the paraffin spot continued to migrate with the solvent front, allowing better distinction between these two compounds. The paraffin nature of the abnormal spot was confirmed for patient 1 by comparative infrared spectroscopy and gas liquid chromatography of the spot. Liquid paraffin was never found by TLC in the BALF from the patients with PAP. asthma inhalers
Most cases of liquid paraffin pneumonitis are diagnosed at necropsy, following operations for suspected bronchial carcinoma or after open lung biopsy. Transthoracic needle biopsy has been used for diagnosis of lipoid pneumonitis, but false negative results are possible. Histologic changes are dominated by large amounts of vacuolated macrophages in the alveoli and to a lesser extent, in the interstitium and peribronchial lymph nodules. Inflammatory cells, mul-tinuclear giant cells, and various degrees of interstitial fibrosis also are present. The vacuoles of macrophages are empty on conventionally fixed sections and only slightly stained by the specific dyes for lipids, Sudan III, Sudan IV, and Black Sudan on fresh frozen sections. Liquid paraffin may finally be identified in the lung specimen by gas chromatography or infrared spectroscopy.