Tinea capitis is a cutaneous fungal infection of the scalp. The disease is
primarily caused by dermatophytes in the Trichophyton and Microsporum genera that
invade the hair shaft. The clinical presentation is typically single or
multiple patches of hair loss, sometimes with a 'black dot' pattern, that may be
accompanied by inflammation, scaling, pustules, and itching. Uncommon in
adults, tinea capitis is predominantly seen in pre-pubertal children, more
often boys than girls. At least eight species of dermatophytes
are associated with tinea capitis. Cases of Trichophyton infection predominate
from Central America to the United States and in parts of Western Europe.
Infections from Microsporum species are mainly in South America, Southern and
Central Europe, Africa and the Middle East. The disease is infectious and can
be transmitted by humans, animals, or objects that harbor the fungus. The
fungus can also exist in a carrier state on the scalp, without clinical
symptomatology. Treatment of tinea capitis requires an oral antifungal
agent; griseofulvin is the most commonly used drug, but other newer antimycotic
drugs, such as terbinafine, itraconazole, and fluconazole have
started to gain acceptance. Symptoms
It may appear as thickened, scaly, and sometimes boggy swellings, or as
expanding raised red rings. Common symptoms are severe itching of the
scalp, dandruff, and bald patches where the fungus has rooted itself in the
skin. It often presents identically to dandruff or seborrheic dermatitis. The
highest incidence in the United States of America is in American boys of school
age. There are three type of tinea capitis,
microsporosis, trichophytosis, and favus; these are based on the causative
microorganism, and the nature of the symptoms. In microsporosis, the lesion
is a small red papule around a hair shaft that later becomes scaly;
eventually the hairs break off 1–3 mm above the scalp. This disease used to be
caused primarily by Microsporum audouinii, but in Europe, M. canis is
more frequently the causative fungus. The source of this fungus is typically
sick cats and kittens; it may be spread through person to person contact, or by
sharing contaminated brushes and combs. In the United States, Trichophytosis is
usually caused by Trichophyton tonsurans, while T. violaceum is more
common in Eastern Europe, Africa, and India. This fungus causes dry,
non-inflammatory patches that tend to be angular in shape. When the hairs break
off at the opening of the follicle, black dots remain. Favus is caused by T.
schoenleinii, and is endemic in South Africa and the Middle East. It is
characterized by a number of yellowish, circular, cup-shaped crusts grouped in
patches like a piece of honeycomb, each about the size of a split pea, with a
hair projecting in the center. These increase in size and become crusted
over, so that the characteristic lesion can only be seen around the edge of the
scab. Diagnosis
Tiniea capitis may be difficult to distinguish from other skin diseases
that cause scaling, such as psoriasis and seborrhoeic dermatitis; the basis
for the diagnosis is positive microscopic examination and microbial
culture of epilated hairs. Wood's lamp examination will reveal bright green to
yellow-green fluorescence of hairs infected by M. canis, M. audouinii, M.
rivalieri, and M. ferrugineum and a dull green or blue-white color of hairs
infected by T. schoenleinii. Individuals with M. canis infection trichoscopy will
show characteristic small comma hairs. Histopathology of scalp biopsy shows
fungi sparsely distributed in the stratum corneum and hyphae extending
down the hair follicle, placed on the surface of the hair shaft. These
findings are occasionally associated with inflammatory tissue reaction in the
local tissue. Treatment
The treatment of choice by dermatologists is a safe and inexpensive
oral medication, griseofulvin, a secondary metabolite of the fungus
Penicillium griseofulvin. This compound is fungistatic and works by affecting
the microtubular system of fungi, interfering with the mitotic spindle and
cytoplasmic microtubules. The recommended pediatric dosage is 10 mgday
for 6–8 weeks, although this may be increased to 20 mgd for those infected
by T. tonsurans, or those who fail to respond to the initial 6 weeks of
treatment. Unlike other fungal skin infections that may be treated with
topical therapies like creams applied directly to the afflicted area,
griseofulvin must be taken orally to be effective; this allows the drug to
penetrate the hair shaft where the fungus lives. The effective therapy rate
of this treatment is generally high, in the range of 88–100%. Other oral
antifungal treatments for tinea capitis also frequently reported in the
literature include terbinafine, itraconazole, and fluconazole; these
drugs have the advantage of shorter treatment durations than griseofulvin.
However, concern has been raised about the possibility of rare side effects
like liver toxicity or interactions with other drugs; furthermore, the newer drug
treatments tend to be more expensive than griseofulvin.
On September 28, 2007, the U.S. Food and Drug Administration stated that Lamisil
is a new treatment approved for use by children aged 4 years and older. The
antifungal granules can be sprinkled on a child's food to treat the infection.
Lamisil carries hepatotoxic risk, and can cause a metallic taste in the mouth.
Pathophysiology From the site of inoculation, the fungus
grows down into the stratum corneum, where it invades keratin. Dermatophytes
are unique in that they produce keratinase, which enables them to use
keratin as a nutrient source. Infected hairs become brittle, and after three
weeks, the clinical presentation of broken hairs is evident.
There are three types of infection: Ectothrix: Characterized by the growth
of fungal spores on the exterior of the hair shaft. Infected hairs usually
fluoresce greenish-yellow under a Wood lamp. Associated with Microsporum canis,
Microsporum gypseum, Trichophyton equinum, and Trichophyton verrucosum.
Endothrix: Similar to ectothrix, but characterized by arthroconidia
restricted to the hair shaft, and restricted to anthropophilic bacteria.
The cuticle of the hair remains intact and clinically this type does not have
florescence. Associated with Trichophyton tonsurans and Trichophyton
violaceum, which are anthropophilic. Favus: Causes crusting on the surface of
the skin, combined with hair loss. Associated with Trichophyton
schoenleini. Epidemiology
Tinea capitis caused by species of Microsporum and Trichophyton is a
contagious disease that is endemic in many countries. Affecting primarily
pre-pubertal children between 6 and 10 years, it is more common in males than
females; rarely does the disease persist past age sixteen. Because spread is
thought to occur through direct contact with afflicted individuals, large
outbreaks have been known to occur in schools and other places where children
are in close quarters; however, indirect spread through contamination with
infected objects may also be a factor in the spread of infection. In the USA,
tinea capitis is thought to occur in 3-8% of the pediatric population; up to
one-third of households with contact with an infected person may harbor the
disease without showing any symptoms. The fungal species responsible for
causing tinea capitis vary according to the geographical region, and may also
change over time. For example, Microsporum audouinii was the
predominant etiological agent in North America and Europe until the 1950s, but
now Trichophyton tonsurans is more common in the USA, and becoming more
common in Europe and the United Kingdom. This shift is thought to be due to the
widespread use of griseofulvin, which is more effective against M. audounii than
T. tonsurans; also, changes in immigration patterns and increases in
international travel have likely spread T. tonsurans to new areas. Another
fungal species that has increased in prevalence is Trichophyton violaceum,
especially in urban populations of the United Kingdom and Europe.
See also List of cutaneous conditions
Ringworm affair Footnotes
References Richardson M.. Fungal Infection:
Diagnosis and Management. Cambridge, MA: Blackwell Publishers. ISBN
1-4051-1578-5. External links