Pseudochylothorax, also known as chyliform effusion rich in cholesterol crystals, is a rare entity that sometimes occurs in long-standing rheumatoid arthritis (RA) and is usually associated with thickened pleura.

What causes Pseudochylous effusion?

A chyliform (pseudochylous) effusion is an uncommon disease entity which develops after an exudative effusion is in situ for a long time. It is commonly initiated by a tuberculous pleurisy and it is important to exclude the presence of active tuberculosis.

Is chylous effusion an exudate?

Although chyle is reported to have protein concentrations in the transudative range, chylous effusions are typically exudative, as defined by the standard criteria.