120 An Introduction to Medical Mycology 



(2) Chronic infection— li\ the chronic form there is a simple inflamma- 

 tory process in the upper part of the cutis. The vessels arc slightly dilated; 

 cellular elements are of the small round type and are sparse. There is mod- 

 crate interstitial edema. The epidermis is slightly acanthotic. At times there 

 is marked hyperkeratosis. The basal cell margin is intact. There is no inter- 

 cellular edema, spongiosis or vesicle formation; occasional areas of para- 

 keratosis are noted. 



( h ) Differential diagnosis.— As in the diagnosis of other forms of 

 mycotic infection, laboratory methods should be employed for every pa- 

 tient suspected of having this fungous disease. The information to be ob- 

 tained by such studies is frequently the only means of definitely establish- 

 ing the diagnosis. 



(1) Interdigital lesions.— If the infection is present on the interdigital 

 webs of the feet alone, it may be impossible to determine the species of 

 infecting micro-organism by clinical observation. If all the webs are affected, 

 infection with M. albicans is probable. The bright red base and overhanging 

 collaret of skin suggest moniliasis. Intertrigo caused by T. purpureum or by 

 T, gypseum may be indistinguishable. There are a number of instances of 

 failure to demonstrate a pathogenic fungus. In some of these cases certain 

 bacteria, especially strains of hemolytic streptococci, have come under 

 suspicion without decision. 



Scaling between the toes due to the injudicious use of strong chemicals 

 may lead the physician astray. Several instances of this character have come 

 under our observation. The lack of laboratory confirmation and healing 

 under bland applications tend to rule out tinea pedis. Maceration of the 

 interdigital webs without evidence of inflammation may be caused by in- 

 creased perspiration or by lack of drying after the bath. Such tissue is vul- 

 nerable to pathogenic fungi and to bacteria. 



Syphilis may produce lesions difficult to distinguish from those of acute 

 tinea pedis. The bright red, fleshy, exudative character should make one 

 suspicious, and examination for condylomas or other evidence of the infec- 

 tion will be fruitful. 



Soft corns are not uncommon and may be found in association with a 

 fungous infection. They are, however, caused not by a fungus but by pres- 

 sure of ill-fitting shoes. When they are present at the base of the web they 

 may on superficial examination suggest tinea pedis. 



(2) Acute inflammatory tinea pedis.— Acute tinea of the feet, caused 

 most commonly by T. gypseum, is usually accompanied by interdigital 

 maceration. It should be remembered, however', that inflammation of the 

 foot and tinea of the webs may be unrelated disorders. In most cases of 

 inflammatory tinea the 4 reaction to the trichophytin test is positive. 



