suppress immune responses, although the mechanism of action remains unknown. Trichophyton rubrum infection has been associated with the induction of an id reaction in which an infection in one part of the body induces an immune response in the form of a sterile rash at a remote site. The most common clinical forms of T. rubrum infection are described below. Foot Trichophyton rubrum is one of the most common causes of chronic tinea pedis commonly known as athlete's foot. Chronic infections of tinea pedis result in moccasin foot, in which the entire foot forms white scaly patches and infections usually affect both feet. Individuals with tinea pedis are likely to have infection at multiple sites. Infections can be spontaneously cured or controlled by topical antifungal treatment. Although T. rubrum tinea pedis in children is extremely rare, it has been reported in children as young as two years of age. Hand Tinea manuum is commonly caused by T. rubrum and is characterized by unilateral infections of the palm of the hand. Groin Along with E. floccosum, T. rubrum is the most common cause of this disease, also known as 'jock itch.' Infections cause reddish brown lesions mainly on the upper thighs and trunk, that are border by raised edge. Nail Once considered a rare causative agent, T. rubrum is now the most common cause of invasive fungal nail disease (called onychomycosis or tinea unguium). Nail invasion by T. rubrum tends to be restricted to the underside of the nail plate and is characterized by the formation of white plaques on the lunula that can spread to the entire nail. The nail often thickens and becomes brittle, turns brown or black. Infections by T. rubrum are frequently chronic, remaining limited to the nails of only one or two digits for many years without progression. Spontaneous cure is rare. These infections are usually unresponsive to topical treatments and respond only to systemic therapy. Although it is most frequently seen in adults, T. rubrum nail infections have been recorded in children. Epidemiology It is thought that Trichophyton rubrum evolved from a zoophilic ancestor, establishing itself ultimately as an exclusive agent of dermatophytosis on human hosts. Genetic analyses of T. rubrum have revealed the presence of heat shock proteins, transporters, metabolic enzymes and a system of up-regulation of key enzymes in the glyoxylate cycle. The species secretes more than 20 different proteases, including exopeptidases and