most commonly infected with tinea capitis. Trichophyton tonsurans is the most common cause of out breaks of tinea capitis in children, and is the main cause of endothrix (inside hair) infections. Trichophyton rubrum is also a very common cause of favus, a form of tinea capitis in which crusts are seen on the scalp. Infected hair shafts are broken off just at the base, leaving a black dot just under the surface of the skin, and alopecia can result. Scraping these residual black dot will yield the best diagnostic scrapings for microscopic exam. Numerous green arthrospores will be seen under the microscope inside the stubbles of broken hair shafts at 400×. Tinea capitis cannot be treated topically, and must be treated systemically with antifungals. Tinea manuum or ringworm of the hands In most cases of tinea manuum, only one hand is involved. Frequently both feet are involved concurrently, thus the saying "one hand, two feet". Onychomycosis, tinea unguium, or ringworm of the nail See Onychomycosis Tinea incognito Ringworm infections modified by corticosteroids, systemic or topical, prescribed for some pre-existing pathology or given mistakenly for the treatment of misdiagnosed tinea. Pathogenesis In order for dermatophytoses to occur, the fungus must directly contact the skin. Likelihood of infection is increased if the skin integrity is compromised, as in minor breaks. The fungi use various proteinases to establish infection in the keratinized stratum corneum. Some studies also suggest that a class of proteins called LysM coat the fungal cell walls to help the fungi evade host cell immune response. The course of infection varies between each case, and may be determined by several factors including: "the anatomic location, the degree of skin moisture, the dynamics of skin growth and desquamation, the speed and extent of the inflammatory response, and the infecting species." The ring shape of dermatophyte lesions result from outward growth of the fungi. The fungi spread in a centrifugal pattern in the stratum corneum, which is the outermost keratinized layer of the skin. For nail infections, the growth initiates through the lateral or superficial nail plates, then continues throughout the nail. For hair infections, fungal invasion begins at the hair shaft. Symptoms manifest from inflammatory reactions due to the fungal antigens. The rapid turnover of desquamation, or skin peeling, due to inflammation limits dermatophytoses, as the fungi are pushed out of the skin. Dermatophytoses rarely cause serious illness, as the fungi