Overview
Tinea capitis, commonly known as scalp ringworm, is a fungal infection that affects the scalp and hair shafts. It is characterized by itchy, scaly patches that often lead to hair loss. Despite its name, no worms are involved. The term “ringworm” is derived from the ring-like appearance of the infection on the skin. Tinea capitis primarily affects children but can also occur in adults, particularly those with weakened immune systems.
Causes of Tinea Capitis
Tinea capitis is caused by dermatophytic fungi, which thrive in keratinized tissues such as hair and nails. Common causative species include Trichophyton and Microsporum. These fungi can be transmitted through direct contact with infected individuals or animals, as well as through contact with contaminated objects like combs, towels, and bedding. The fungi can remain viable on these surfaces for extended periods, facilitating the spread of infection.
Fungal Species
Dermatophytes can be categorized based on their preferred hosts:
- Anthropophilic Species (Human Preference):
- Trichophyton tonsurans: Common in the United States.
- Trichophyton violaceum: Seen in individuals from Africa or the Middle East.
- Other examples include Trichophyton soudanense, Trichophyton schoenleinii, Trichophyton rubrum, and Microsporum audouinii.
- Zoophilic Species (Animal Preference):
- Microsporum canis: Common in Europe and New Zealand, originating from cats.
- Other species include Microsporum nanum (pigs), Microsporum distortum (a variant of M. canis), Trichophyton equinum (horses), and Trichophyton verrucosum (cattle).
- Geophilic Species (Soil Preference):
- Microsporum gypseum: Rarely causes tinea capitis but originates from soil.
Symptoms of Tinea Capitis
Symptoms of tinea capitis can vary significantly depending on the fungal species involved, the type of hair invasion, and the host’s inflammatory response. Common symptoms include:
Non-inflammatory Variants:
- Gray Patch: Fine scaling of the scalp and patches of alopecia (hair loss) that appear gray due to spores coating the affected hairs. Erythema (redness) is usually minimal with anthropophilic species but can be marked with zoophilic or geophilic species.
- Black Dot: Fine scaling with patches of alopecia, characterized by black dots where the hair shafts have broken off.
- Diffuse Scale: Resembles generalized dandruff; alopecia is subtle or absent.
Inflammatory Variants:
- Diffuse Pustular: Patchy alopecia with associated pustules or folliculitis. Secondary infection with bacteria or other fungi may occur.
- Kerion: A severe inflammatory reaction resulting from a delayed immune response to the fungus. This manifests as a painful, erythematous, boggy plaque with associated alopecia and scattered pustules. It is usually caused by a zoophilic species and may result in permanent alopecia.
- Favus: A chronic inflammatory infection characterized by matted hair and the formation of yellow, crusted cup-shaped lesions (scutula) around the base of the hairs. Scutula contain hyphae and keratin debris and may coalesce to form a large mass.
Diagnosis of Tinea Capitis
The diagnosis of tinea capitis is typically based on clinical presentation and confirmed through laboratory tests. Key diagnostic methods include:
- Microscopy and Culture: Samples of hair or scalp skin are taken for microscopic examination and culture to identify the presence of fungal elements. This is the gold standard for confirming tinea capitis.
- Wood’s Lamp Examination: This diagnostic tool uses ultraviolet light to detect fluorescence in infected hairs. Certain species of fungi, such as Microsporum species, exhibit bright green fluorescence under a Wood’s lamp, aiding in the identification of affected hairs for sample collection.
- KOH Stain: Potassium hydroxide (KOH) preparation involves placing a sample of the infected area on a slide with KOH solution. The KOH dissolves keratin, making fungal elements more visible under a microscope.
- PCR (Polymerase Chain Reaction): This advanced diagnostic technique can identify fungal DNA in samples, providing a rapid and accurate diagnosis.
Treatment of Tinea Capitis
Effective treatment of tinea capitis requires systemic antifungal medications because topical treatments alone are insufficient. Common treatment options include:
Oral Antifungal Medications:
- Griseofulvin: Typically prescribed for a duration of 6-8 weeks. It is the only oral antifungal approved for use in children.
- Terbinafine: Often considered the first choice due to its effectiveness. It is usually prescribed for 4 weeks.
- Itraconazole and Fluconazole: Other options that may be used depending on the specific fungal species and patient response.
Medicated Shampoos:
Shampoos containing 2% ketoconazole or 1% selenium sulfide are recommended for twice-weekly use to reduce fungal spores and prevent the spread of infection. These shampoos are not curative on their own but help control the spread.
Complications of Tinea Capitis
If left untreated, tinea capitis can lead to several complications, including:
- Scarring Alopecia: Permanent hair loss due to scarring of the scalp.
- Secondary Bacterial Infections: These can occur if the affected area is scratched or if there is significant inflammation.
- Kerion Formation: A severe inflammatory response that can result in scarring and permanent hair loss.
- Dermatophytid Reaction: An allergic reaction to the fungus that can cause a rash on other parts of the body, such as the hands or feet.
Prevention
Preventing tinea capitis involves measures to reduce exposure to the fungi and minimize the risk of transmission. Key strategies include:
- Education: Teaching children and caregivers about the infection, its transmission, and preventive measures is crucial.
- Hygiene Practices: Regular hair washing, especially after haircuts, and maintaining clean and dry skin can help prevent infection. Avoid sharing personal items like combs, brushes, hats, towels, and bedding.
- Environmental Cleanliness: Regularly cleaning and disinfecting common areas, especially in schools, childcare centers, gyms, and locker rooms, is essential. Ensuring that pets, especially those that go outdoors, are regularly checked by a veterinarian for fungal infections.
- Screening and Early Treatment: Early identification and treatment of infected individuals can help prevent the spread within households and communities. In cases of outbreaks, screening of classmates, family members, and close contacts may be necessary.
Conclusion
Tinea capitis is a common fungal infection affecting primarily children but also adults with weakened immune systems. Understanding its causes, symptoms, and treatment options is essential for effective management and prevention. Early diagnosis and prompt treatment with systemic antifungal medications are crucial to prevent complications and the spread of the infection. Preventative measures, including education, hygiene practices, and environmental cleanliness, play a vital role in controlling the spread of tinea capitis within communities.
References
Mayo Clinic Staff. (2022). Ringworm (scalp) – Symptoms & causes. Mayo Clinic. Retrieved from https://www.mayoclinic.org.
Mayo Clinic Staff. (2022). Ringworm (scalp) – Diagnosis & treatment. Mayo Clinic. Retrieved from https://www.mayoclinic.org.
DermNet NZ. Tinea Capitis. Retrieved from https://dermnetnz.org/topics/tinea-capitis.
British Association of Dermatologists. Tinea Capitis. Retrieved from https://www.bad.org.uk.
