Blastomyces dermatitidis with large yeast forms

Yeast forms of Blastomyces dermatitidis typically range from 8 to 20 microm in largest diameter. We report a rare case of primary pulmonary blastomycosis with an unusual morphology, in which we found significant numbers of large yeast forms ranging from 30 to 35 microm in diameter. To our knowledge, this is only the second reported case of giant forms of B dermatitidis. We also review the literature and discuss the possible association of this unusual morphology with immunosuppression in general and glucocorticoid use in particular.