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Fig. 6.59 A-D. Skeletal paracoccidioidomycosis. A The chest radiograph of an 11-year-old boy with mediastinal enlargement and multiple osteolytic foci in the scapula, upper humerus, and ribs. B The same patient: there are multiple sharply demarcated cortical osteolytic lesions in the humeri and scapulae. The shoulder joints, particularly the left, are also infected and there is a lytic focus in the right acromium. There is no evidence of sclerosis around any of these lytic lesions. C The skull of the same patient also shows multiple small osteolytic lesions. D A different patient, an adult male, with a large osteolytic lesion in the os calcis. It is possible that this is the result of a wound in the heel, allowing direct inoculation. (Courtesy of Dr. I. L. Aymore, CLAP, Rio de Janeiro)

 

Fig. 6.60 A-C. Lobomycosis: infection with Loboa Ioboi forms a variety of lesions, easily mistaken for keloids (Fig. 6.1 B). A Tumoral form of lobomycosis. B Histopathology shows no fibrosis but diffuse infiltration of the dermis with many Loboa loboi cells. PAS, x64. C Successive budding results in chains of cells connected together. Gomori methenamine-silver, x200 (inset, x500). (A-C from Bittencourt and Londero 1995; A also courtesy of Dr. S. Marques, S. Luis, Brazil)

 

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Candidiasis

Hippocrates recognized oral thrush in the fourth century B. C. and described a disseminated form in two patients. By the eighteenth and nineteenth centuries there were many descriptions and further confirmation that this could become a systemic disease, even involving the brain. By 1877 it was known that the fungus was dimorphic, appearing as either yeast or mycelia: 20 years later it was realized that the different forms depended on environmental conditions. From then on the number of different species recognized and named grew considerably. Moniliasis was the name used by many experts, but in 1954 Candida became the agreed generic name.

In the first edition on this textbook there was a separate small section on Torulopsis glabrata, but the species has now been reclassified as C. glabrata: the group name monilia has also been discarded. One may perhaps wonder what any of these fungi will be called in future editions of this book!

Synonyms

Moniliasis. Thrush. Bronchomycosis. Tea taster's cough. Mycotic vulvovaginitis. Ger: Candidiasis. Fr: Candidiose. Sp: Candidiasis.

Definition

Candidiasis is an infection by one of the group of fungi of the genus Candida. Most of the Candida spp. are commensal and part of the normal flora in the mouth, pharynx, colon, vagina, and skin. Its presence therefore does not imply a pathological state unless there is evidence of tissue invasion or there has been an overwhelming increase in the number of fungi.

Geographic Distribution

The yeast and hyphae which cause candidiasis are everywhere, associated with warm-blooded animals. They have been extensively studied in the mouth, rectum, vagina, and skin of healthy people. There is no significant geographic variation.

Epidemiology and Pathology

There are more than 80 species of Candida, but only a few are pathogenic in humans. The commonest cause of candidiasis is Candida albicans, a normal commensal in the mouth and upper respiratory and intestinal tracts. Another common fungus is C. tropicalis. The various species probably have a predilection for different clinical sites: for example, C. albicans and C. parapsilosis are the most common causes of endocarditis, while C. tropicalis frequently causes disseminated infections in immunosuppressed patients and many of those with hematological malignancies. C. krusei infects neutropenic patients and gives children diarrhea. It is invasive in patients with septicemia. Many other species have been occasionally isolated and have been cultured from a very wide range of environmental sources.

Candida spp., particularly C. albicans, have been isolated from animals. If found in food or drinks (fruit juices are often contaminated) this is a reflection of the packaging and processing rather than the fruit juice. While the risk posed to healthy individuals is slight, for those who are immunosuppressed the risk is considerable and the infection can be fatal.

Candida are larger than bacteria and are gram-positive; all species can reproduce by budding, forming blastospores. Elongation of these yeast cells, with branching, can produce hyphae, the species varying in the way that these are produced. C. albicans can produce cylindrical germ tubes, which are rudimentary hyphae, from blastospores. Candida grows on a wide variety of common culture media, but most often is grown on Sabouraud's agar. There is a skin test which indicates prior sensitization by C. albicans, but many healthy adults react positively so that the test has little clinical use. The Candida spp. are opportunistic: they can produce toxic effects and potentially tissue-digesting enzymes such as protease and phospholipase. Gram stains and the periodic acid-Schiff stain show the fungi in tissue sections. Sometimes the tissue reaction is suppurative and without a contrast stain the fungi may be overlooked; in other cases the reaction is granulomatous and suggests tuberculosis, so it is important for pathologists to utilize special stains for fungi whenever there is any possibility of a mycosis.

Candidiasis may be cutaneous, mucocutaneous, or systemic. The papular dermatitis produced by C. albicans has no imaging characteristics. There is a marked inflammatory response causing an edematous, shiny erythema. This may be acute or chronic and is often extensive and progressive. This infection does not spread to deeper underlying tissues, but there may be vascular invasion and dissemination.

Mucocutaneous candidiasis is most commonly seen as oral thrush or vaginal, penile, or rectal infections. Again, there are no specific imaging findings. The systemic candidal infections do cause changes which are important for the imaging department.


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