Question

The mother of a seven-year-old boy notices that he is scratching his head frequently. On close examination she notices a grayish, round, and roughened area where the hair has broken off. Examination by the child's pediatrician produces a diagnosis of tinea capitis.

1. Explain the cause of the infection and proposed possible mechanisms for spread of infection in school-age children, particularly during winter months.

2. What methods are commonly used in the diagnosis  superficial fungal infections?

Answer 1

1. Tinea capitis is a disease caused by a fungi called dermatophytes. It is a, superficial fungal infection of the skin of the scalp, eyebrows, and eyelashes, with a propensity for attacking hair shafts and follicles. The disease is considered to be a form of superficial mycosis or dermatophytosis.

It is a highly contagious infection that’s usually spread through person-to-person contact or by sharing combs, towels, hats, or pillows. House pets, such as cats and dogs, can spread ringworm, too. Farm animals like goats, cows, horses, and pigs can also be carriers. However, these animals might not show any signs of infection. Dermatophytes prefer warmth and moisture. Overcrowding and poor hygiene increase the spread of ringworm.

The dermatophytes grow within dead, keratinized tissue only. The fungal cells produce keratinolytic proteases in vivo and in vitro which provide means of entry into living cells. The 29 fungal metabolic products diffuse through the Malphigian layer of epidermis to cause erythema, vesicles and pustules. The fungal hyphae grow rapidly, become old, break into arthrospores and are shed off from the epidermis. Dermatophytes colonize the horny layers of the skin, hair and nails initially. The dermatophytic infection spreads centrifugally in all directions on the glabrous skin showing the classical ringworm pattern. However, it is still not clear how dermatophytic fungi regulate the utilization of different proteases against various cornified layers of the host in addition to the other roles played by these proteins especially in adherence or immunomodulation etc. When compared to the other fungal diseases, dermatophytes infect the immunocompetent patients irrespective of the other fungal diseases where the incidence is more in immunocopromised patients. The dermatophytic infection can be acute and may rapidly be eliminated through efficient host immune responses

1. Diagnosis of tinea capitis usually can be made by clinical features alone, especially when occipital or postauricular lymphadenopathy is present. physical examination, assisted by the use of a Wood's lamp. Skin scrapings prepared with potassium hydroxide for microscopic examination, or a cotton swab for fungal culture, usually are diagnostic