Morphology of Medically Important Fungi, 2nd Edition


absidiaThis web site is intended to help laboratory medicine residents and technologists identify clinically important fungi. Unlike much bacterial identification in the modern clinical microbiology laboratory, medical mycology often relies on morphology to establish a diagnosis. This site attempts to provide order in the sometimes confusing realm of fungal morphology. Poisoning from ingestion of fungi, non-medical mycology, and other elements of diagnosis including molecular and biochemical testing are not discussed in these pages.


a. nidulusFungi are eukaryotes that have cell walls composed of chitin with or without cellulose. They are ubiquitous and comprise an estimated 250,000 species, of which only about 150 have been shown to cause disease in humans. They are chemoheterotrophic saprophytes. Morphology remains an important tool for speciating fungi, especially filamentous fungi, although morphologic clues can also be useful in the identification of yeast species.

Basic Premise:

chaetomiumMorphology is essentially a comparative art: it is learned most easily when images can be quickly juxtaposed. While there is no substitute for experience, a great deal of morphology can be learned by study, especially when images are assembled in a way that assists recall. Like any other skill, morphology is a matter of practice. This web site attempts to simplify the learning process by allowing rapid comparison of different fungal organisms. Unlike an atlas or chapter, HTML allows nonlinear exploration of the subject matter and more convenient reference to important terminology and concepts. I hope that this web site serves pathology and laboratory medicine residents as both a basic primer in fungal morphology and as a study aid for board examinations.

How To Use These Pages:

epicoccumThis site is organized into several pages that can be viewed by selecting the underlined text in the column at the left of each major page. The Medically Important Fungi are separated into seven categories without regard to phylogenetic relationships; this page serves as a hub around which most of the discussion is organized. Since the nomenclature of medical mycology can be complicated, a page of Definitions is included to help the beginner. Finally, a brief bibliography and Other Web Resources are listed on a separate page. No work of this size can be completed without the generous help of many individuals; special Acknowledgement is due the kind and patient technologists, laboratory supervisors, and pathologists who made this work possible.

This site was hand written and tested using Microsoft Internet Explorer®. For best results, download the latest version from Microsoft. This site was developed by William McDonald, MD while a resident in Pathology at UCSF. Questions, comments, and corrections can be addressed to Enrique Terrazas, MD.


To use these pages as a tutorial, jump to Medically Important Fungi to begin. To use these pages as an atlas, jump to Site Map to begin.

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Revised: 29 January 2003