Detached single cilia: another potential pseudomicrobe seen in bronchoalveolar lavage specimens

High magnification examination of Romanovsky-stained bronchoalveolar lavage (BAL) material may be needed, if one is to confidently exclude small organisms such as toxoplasmosis, histoplasmosis, and the negative images of mycobacteria. Pseudomicrobes have been described, and detailed criteria must be carefully applied, if incorrect diagnoses are to be avoided. We recently noted numerous free-lying, uniform, eosinophilic, straight or slightly curved bacilliform structures in such a specimen. These were seen on Diff-Quik-stained material, but were extremely pale on Papanicolaou-stained slides. Comparison with the cilia of contaminating bronchial cells showed these pseudomicrobes to have similar length, diameter, and tinctorial properties. Electron microscopy of the sedimented cell pellet showed isolated, detached single cilia (DSC) far removed from any bronchial cells. Twenty BAL's from 13 males and seven females (median age = 48.5) undergoing infection surveillance were then retrospectively reviewed. DSC were present in 16 specimens (80%), but were rare in three of these. Although present in cases with prominent bronchial cell contamination (n = 6 cases), DSC were also encountered when ciliated cells were rare (n = 13), or absent (n = 1). Familiarity with these distinctive structures should make it unlikely that they will be mistaken for infectious organisms.