|Tinea of the scalp|
Tinea capitis (also known as "herpes tonsurans","ringworm of the hair", "ringworm of the scalp", "scalp ringworm", and "tinea tonsurans" ) is a cutaneous fungal infection (dermatophytosis) of the scalp. The disease is primarily caused by dermatophytes in the genera Trichophyton and Microsporum that invade the hair shaft. The clinical presentation is typically single or multiple patches of hair loss, sometimes with a 'black dot' pattern (often with broken-off hairs), 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.
It may appear as thickened, scaly, and sometimes boggy swellings, or as expanding raised red rings (ringworm). 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 (scutula) 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.
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 (arthroconidia) on the exterior of the hair shaft. Infected hairs usually fluoresce greenish-yellow under a Wood's lamp (blacklight). 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 fluorescence. 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 .
Tinea 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.
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 (inhibiting the growth or reproduction of fungi) and works by affecting the microtubular system of fungi, interfering with the mitotic spindle and cytoplasmic microtubules. The recommended pediatric dosage is 10 mg/kg/day for 6–8 weeks, although this may be increased to 20 mg/kg/d 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 affected 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. A 2016 meta-analysis of randomized controlled trials found that terbinafine, itraconazole and fluconazole were at least equally effective as griseofulvin for children infected with Trichophyton, and terbinafine is more effective than griseofulvin for children with T. tonsurans infection. However, concerns have 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 (Terbinafine hydrochloride, by Novartis AG) 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. [ citation needed ]Lamisil carries hepatotoxic risk, and can cause a metallic taste in the mouth.
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 affected 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 ( fomites ) may also be a factor in the spread of infection. In the US, 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 US, 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.
Athlete's foot, known medically as tinea pedis, is a common skin infection of the feet caused by a fungus. Signs and symptoms often include itching, scaling, cracking and redness. In rare cases the skin may blister. Athlete's foot fungus may infect any part of the foot, but most often grows between the toes. The next most common area is the bottom of the foot. The same fungus may also affect the nails or the hands. It is a member of the group of diseases known as tinea.
Griseofulvin is an antifungal medication used to treat a number of types of dermatophytoses (ringworm). This includes fungal infections of the nails and scalp, as well as the skin when antifungal creams have not worked. It is taken by mouth.
Dermatophyte is a common label for a group of fungus of Arthrodermataceae that commonly causes skin disease in animals and humans. Traditionally, these anamorphic mold genera are: Microsporum, Epidermophyton and Trichophyton. There are about 40 species in these three genera. Species capable of reproducing sexually belong in the teleomorphic genus Arthroderma, of the Ascomycota. As of 2019 a total of nine genera are identified and new phylogenetic taxonomy has been proposed.
Tinea corporis is a fungal infection of the body, similar to other forms of tinea. Specifically, it is a type of dermatophytosis that appears on the arms and legs, especially on glabrous skin; however, it may occur on any superficial part of the body.
Dermatophytosis, also known as ringworm, is a fungal infection of the skin. Typically it results in a red, itchy, scaly, circular rash. Hair loss may occur in the area affected. Symptoms begin four to fourteen days after exposure. Multiple areas can be affected at a given time.
Kerion or kerion celsi is an acute inflammatory process which is the result of the host's response to a fungal ringworm infection of the hair follicles of the scalp that can be accompanied by secondary bacterial infection(s). It usually appears as raised, spongy lesions, and typically occurs in children. This honeycomb is a painful inflammatory reaction with deep suppurative lesions on the scalp. Follicles may be seen discharging pus. There may be sinus formation and rarely mycetoma-like grains are produced. It is usually caused by dermatophytes such as Trichophyton verrucosum, T. mentagrophytes, and Microsporum canis. Treatment with oral griseofulvin common.
Tinea manuum is a fungal infection of the hand, mostly a type of dermatophytosis, often part of two feet-one hand syndrome. There is diffuse scaling on the palms or back of usually one hand and the palmer creases appear more prominent. When both hands are affected, the rash looks different on each hand, with palmer creases appearing whitish if the infection has been present for a long time. It can be itchy and look slightly raised. Nails may also be affected.
Trichophyton rubrum is a dermatophytic fungus in the phylum Ascomycota. It is an exclusively clonal, anthropophilic saprotroph that colonizes the upper layers of dead skin, and is the most common cause of athlete's foot, fungal infection of nail, jock itch, and ringworm worldwide. Trichophyton rubrum was first described by Malmsten in 1845 and is currently considered to be a complex of species that comprises multiple, geographically patterned morphotypes, several of which have been formally described as distinct taxa, including T. raubitschekii, T. gourvilii, T. megninii and T. soudanense.
David Gruby was a Hungarian physician born in the village of Kis-Kér to a Jewish farmer. He received his doctorate in Vienna and performed scientific research in Paris.
Trichophyton is a genus of fungi, which includes the parasitic varieties that cause tinea, including athlete's foot, ringworm, jock itch, and similar infections of the nail, beard, skin and scalp. Trichophyton fungi are molds characterized by the development of both smooth-walled macro- and microconidia. Macroconidia are mostly borne laterally directly on the hyphae or on short pedicels, and are thin- or thick-walled, clavate to fusiform, and range from 4 to 8 by 8 to 50 μm in size. Macroconidia are few or absent in many species. Microconidia are spherical, pyriform to clavate or of irregular shape, and range from 2 to 3 by 2 to 4 μm in size.
Microsporum audouinii is an anthropophilic fungus in the genus Microsporum. It is a type of dermatophyte that colonizes keratinized tissues causing infection. The fungus is characterized by its spindle-shaped macroconidia, clavate microconidia as well as its pitted or spiny external walls.
Trichophyton tonsurans is a fungus in the family Arthrodermataceae that causes ringworm infection of the scalp. It was first recognized by David Gruby in 1844. Isolates are characterized as the "–" or negative mating type of the Arthroderma vanbreuseghemii complex. This species is thought to be conspecific with T. equinum, although the latter represents the "+" mating strain of the same biological species Despite their biological conspecificity, clones of the two mating types appear to have undergone evolutionary divergence with isolates of the T. tonsurans-type consistently associated with Tinea capitis whereas the T. equinum-type, as its name implies, is associated with horses as a regular host. Phylogenetic relationships were established in isolates from Northern Brazil, through fingerprinting polymorphic RAPD and M13 markers. There seems to be lower genomic variability in the T. tonsurans species due to allopatric divergence. Any phenotypic density is likely due to environmental factors, not genetic characteristics of the fungus.
Microsporum gypseum is a soil-associated dermatophyte that occasionally is known to colonise and infect the upper dead layers of the skin of mammals. The name refers to an asexual "form-taxon" that has been associated with four related biological species of fungi: the pathogenic taxa Arthroderma incurvatum, A. gypsea, A. fulva and the non-pathogenic saprotroph A. corniculata. More recent studies have restricted M. gypseum to two teleomorphic species A. gypseum and A. incurvatum. The conidial states of A. fulva and A. corniculata have been assigned to M. fulvum and M. boullardii. Because the anamorphic states of these fungi are so similar, they can be identified reliably only by mating. Two mating strains have been discovered, "+" and "–". The classification of this species has been based on the characteristically rough-walled, blunt, club-shaped, multicelled macroconidia. Synonyms include Achorion gypseum, Microsporum flavescens, M. scorteum, and M. xanthodes. There has been past nomenclatural confusion in the usage of the generic names Microsporum and Microsporon.
Microsporum canis is a pathogenic, asexual fungus in the phylum Ascomycota that infects the upper, dead layers of skin on domesticated cats, and occasionally dogs and humans. The species has a worldwide distribution.
Microsporum nanum is a pathogenic fungus in the family Arthrodermataceae. It is a type of dermatophyte that causes infection in dead keratinized tissues such as skin, hair, and nails. Microsporum nanum is found worldwide and is both zoophilic and geophilic. Animals such as pigs and sheep are the natural hosts for the fungus; however, infection of humans is also possible. Majority of the human cases reported are associated with pig farming. The fungus can invade the skin of the host; if it is scratched off by the infected animal, the fungus is still capable of reproducing in soil.
Microsporum gallinae is a fungus of the genus Microsporum that causes dermatophytosis, commonly known as ringworm. Chickens represent the host population of Microsporum gallinae but its opportunistic nature allows it to enter other populations of fowl, mice, squirrels, cats, dogs and monkeys. Human cases of M. gallinae are rare, and usually mild, non-life-threatening superficial infections.
Favus or tinea favosa is the severe form of tinea capitis, a skin infectious disease caused by the dermatophyte fungus Trichophyton schoenleinii. Typically the species affects the scalp, but occasionally occurs as onychomycosis, tinea barbae, or tinea corporis.
Trichophyton verrucosum, commonly known as the cattle ringworm fungus, is a dermatophyte largely responsible for fungal skin disease in cattle, but is also a common cause of ringworm in donkeys, dogs, goat, sheep, and horses. It has a worldwide distribution, however human infection is more common in rural areas where contact with animals is more frequent, and can cause severe inflammation of the afflicted region. Trichophyton verrucosum was first described by Emile Bodin in 1902.
Topical antifungaldrugs are used to treat fungal infections on the skin, scalp, nails, vagina or inside the mouth. These medications come as creams, gels, lotions, ointments, powders, shampoos, tinctures and sprays. Most antifungal drugs induce fungal cell death by destroying the cell wall of the fungus. These drugs inhibit the production of ergosterol, which is a fundamental component of the fungal cell membrane and wall.