ZYGOMYCETES AND ZYGOMYCOSIS
is the term applied to infection with any of a group of zy- gomycetes, the most
common of which are Absidia, Rhizopus,
and Mucor. These fungi are ubiquitous
saprophytes in soil and are commonly found on bread and many other foodstuffs.
They occasionally cause disease in persons with diabetes mellitus and in
im-munosuppressed patients receiving corticosteroid therapy. Diabetic acidosis
has a particu-larly strong association with zygomycosis.
Pulmonary or rhinocerebral disease is acquired by
inhalation of conidia. The pul-monary form has clinical findings similar to
those of other fungal pneumonias; the rhinocerebral form, however, produces a
dramatic clinical syndrome in which agents of zygomycosis show striking
invasive capacity. They penetrate the mucosa of the nose, paranasal sinuses, or
palate, often resulting in ulcerative lesions. Once beyond the mu-cosa, they
progress through tissue, nerves, blood vessels, fascial planes, and often the
vi-tal structures at the base of the brain. The clinical syndrome begins with
headache and may progress through orbital cellulitis and hemorrhage to cranial
nerve palsy, vascular thrombosis, coma, and death in less than 2 weeks.
The pathologic cerebral and pulmonary findings are
distinctive: the zygomycetes in-volved all show ribbon-like nonseptate hyphae in tissue which are
so large their branch points can be difficult to visualize. Conidia are not
seen. As with Aspergillus, tissue
biop-sies are necessary to demonstrate the invasive hyphae, unless they can be
seen on scrap-ings from palatal or nasal ulcers. For reasons that are obscure,
cultures are sometimes negative, even those from tissue containing
characteristic hyphae. Therapy involves con-trol of underlying disease,
amphotericin B, and occasionally surgery.