Question:

A 3-year old boy presented with 3 months history of patchy hair loss. According to his parents, there was a history of pustules which had subsided after treatment from his GP. A cat in his family has skin problem recently. Clinical examination showed multiple patches of alopecia.

Answer: B. Tinea capitis

Tinea capitis is fungal infection of the scalp. It is caused by dermatophyte such as Trichophyton species and Microsporum species. It usually presents as patchy hair loss with variable degree of inflammation. The infected hairs are brittle and broken. In severe cases, kerion which is an inflammatory mass with pustules and purulent discharge can occur. Wood's light examination shows bluish green fluorescent in Microsporum species infection. Plucked hair or scales from the scalp should be collected for fungal culture to isolate the organism. In this case, the Wood's light examination demonstrated bluish green fluorescent. Together with the history of pustules and infected cat at home, the diagnosis is tinea capitis caused by zoophilic dermatophyte such as Microsporum species.

Alopecia areata is characterised by patchy hair loss without any inflammation of the scalp. Exclamation mark hair is characteristic in this condition. It can recover with regrowth of hair or further progress with complete loss of hair of the scalp or even other body hairs. Trichotillomania is a condition due to compulsive behaviour of repeated plucking of hair resulting in patchy hair loss. Scalp folliculitis is characterised by pustules and folliculitis of the scalp.