Section 6: Superficial Fungal Infections

Tinea corporis Superficial fungal infections of the skin are among the most common of all pediatric dermatoses. These are illustrations of more superficial fungal infections of hairless skin. The annular lesions in Figs. 6-1 and 6-2 resulted from infection with Trichophyton tonsurans.

In the cases illustrated, clinical diagnosis of a superficial fungal infection is reasonably certain, and one may guess that the causative fungus is a Microsporum or Trichophyton. A potassium hydroxide preparation of a scale obtained from the edge of a lesion will identify the hyphae.

Tinea corporis In some cases, tinea corporis presents with concentric rings (Fig. 6-3). Definitive diagnosis depends on mycologic culture of the scale from a lesion. In cases of candidiasis, tinea imbricata and favus, the causative organism can frequently and confidently be guessed correctly. In general, one may say that Microsporum canis, Microsporum audouinii, T tonsurans, and T schoenleinii can infect scalp and hairless skin, and Trichophyton rubrum and Candida albicans can infect hairless skin and nails.

Tinea corporis-vesicular On rare occasions, a marked inflammatory response to the presence of a dermatophyte leads to a vesicular or bullous eruption. The clinical presentation seen in Fig. 6-4 must be differentiated from acute contact dermatitis, bullous impetigo, or an autoimmune blistering disease such as linear IgA dermatosis.

Tinea corporis The numerous scaly rings illustrated in Figs. 6-5 and 6-6 are due to M canis. The majority of cases result from exposure to infected cats, many of which have no symptoms of ringworm.

Kittens appear to have a higher frequency of infection than adult cats, and shedding of the fungus occurs more during the winter months. In addition, cats that live both outdoors and indoors appear to be more commonly infected with M canis than do indoor cats.

Tinea corporis (faciei) Infection at the sites shown in Fig. 6-7 may also be termed tinea faciei. Note the ring shape of the active periphery of the lesions in this patient.

Facial lesions may be due to T tonsurans, T rubrum, or T mentagrophytes. Cutaneous infection with zoophilic species, such as M canis, may also occur on the face. As noted in Fig. 6-8...