BLACK DOT RINGWORM

What is black dot ringworm?
Black dot ringworm is a fungal infection of the scalp and can also be referred to as tinea capitis.  Symptoms of scalp ringworm are:

• Distinct round or oval patch of scaly skin on the scalp
• Circular patches that spread into a red outer border with a clear center, giving it the appearance of a ring
• Reddening, crusting and scaling of the scalp
• Mild to intense itching
• Hair loss
• Swollen lymph nodes in the neck

The infection is diagnosed by looking at scalp lesions under a Wood’s lamp.  This is a special lamp that causes the fungus to fluoresce.  Hairs and scales may also be examined under the microscope for the presence of fungi.  Fungal cultures may also help in diagnosis.

What causes black dot ringworm?
Black dot ringworm is caused by the Trichophyton family of fungi and is the most common fungus in the United States.  The infection forms within the hair shaft, making the hair very brittle.  The hair then breaks off at the scalp’s surface around the area where blisters have appeared.  The remaining portion of hair that is left behind creates the appearance of black dots.  The fungus is transmitted from person-to-person, animal-to-person or object-to-person.

How is black dot ringworm treated?
Topical antifungal agents are ineffective in the management of tinea capitis.  If topical agents are used they must be applied until symptoms have resolved and fungal cultures are negative.  Griseofulvin, an oral antifungal agent, is the drug of choice for treatment.  Prednisone, systemic antibiotics and surgical drainage of pus may be required in severe cases.

References:
Wolff K, Johnson, RA.  Fitzpatrick’s Color Atlas and Synopsis of Clinical Dermatology. Sixth Edition. 2009.