FAVUS 



163 



Favus. Favus is caused by Trichophyton Schoenleini in most 

 cases but T. violaceum and Microsporum gypseum occasionally cause 

 clinical favus. The disease occurs not only in man but also in various 

 lower animals, particularly mice, but also cats, dogs, chickens, and 

 some others. The great majority of human cases are contracted by 

 direct or indirect contact with preceding cases, and are due to T. 

 Schoenleini, but some of the species infecting lower animals will 

 also produce the disease in man. 



The disease occurs particularly in the poor and the unclean. It has 

 almost disappeared in the more advanced countries, but is prevalent 

 in southeastern Europe and northern 

 Africa. It occurs more frequently in 

 children than in adults. 



The lesions occur most frequently on 

 the scalp, though other parts of the body 

 surface may be affected, but in the latter 

 case the disease has usually been carried 

 from the scalp. The fungus grows be- 

 tween the outer cornified layer of the skin 

 and the inner layer of epithelial cells 

 (]\Ialpighian layer) and forms a very 

 characteristic yellow, cup-shaped mass, 

 the scutulum. The infection begins in a 

 hair follicle, and the hair is usually seen 

 projecting from the scutulum. "When the 

 latter is pulled off, there is left a raw, sometimes suppurating sur- 

 face. By growth and coalescence of the scutula, there may be 

 formed an extensive crusted layer on the scalp. The hairs become 

 opaque and dull, and finally drop out, leaving bald spots. 



A section through the scutulum shows a radiating feltwork of 

 mycelium, which tends to die off in the center, leaving a granular 

 debris, and to form spores at the periphery. The fungus also invades 

 the shaft of the hair, forming parallel bundles of mycelium through 

 its center. 



The organism may be demonstrated by a microscopic examination 

 of either the scutulum or a hair. A small portion of the former should 

 be crushed under a cover slip in a 10 per cent sodium hydroxide solu- 

 tion; the hair should also be examined in alkah. In the lesions the 

 mycelium is very irregular, its component cells varying considerably 

 in size and form. The cells tend to break apart, giving the filaments 

 an articulated appearance, and the terminal portions of the filaments 



Fig. 81. Favus of the scalp 

 showing crusts or scutula. 



