Caught under the lens

A 12-year-old female patient presented with “dandruff ” on her scalp [Figure 1] for the past 3 months. Trichoscopy (DL 200, ×10, non-polarized, non-contact) revealed an adult head louse moving among the hair on her scalp [Video 1]. Few oval-shaped nits of size around 0.8 × 0.3 mm were also seen attached to the proximal part of the hair shaft. Microscopic examination (× 100) revealed a 2 mm, wingless, dorsoventrally flattened head louse with short antennae, and three pairs of clawed legs [Video 2]. Based on the characteristic trichoscopic and microscopic features, a diagnosis of pediculosis capitis was made and the patient was advised to apply 1% permethrin and wash it after 10 min. This was followed by wet combing. The same treatment was repeated after 1 week with good improvement. The household contacts were screened and treated in the same manner, Pediculosis capitis is transmitted among children through direct contact with an infected scalp. Other manifestations include papular urticaria, pruritus, excoriations, and lymphadenopathy. Head lice are known to carry Staphylococcus aureus and Streptococcus pyogenes. Other organism identified in head lice include Borrelia recurrentis, Bartonella quintana, and Coxiella burnetti.^[1] Pediculosis capitis needs to be differentiated from peripilar keratin casts, scalp psoriasis, and seborrheic dermatitis. Trichoscopy and microscopy are useful noninvasive investigations that help physicians establish the diagnosis in patients with pediculosis capitis.

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Figure 1:

A 12-year-old female patient presented with pediculosis capitis presenting as “dandruff ” on her scalp.

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Management of pediculosis capitis is based on the eradication of living lice and eggs. Topical treatments including permethrin 1% lotion/cream, malathion 0.5% lotion/gel, benzyl alcohol 5% lotion, spinosad 0.9% suspension, and ivermectin 0.5% lotion. If live lice are seen 24 h after the treatment, retreatment with a new drug class might be needed, as resistance is likely. Patients need to be made aware that conditioner should not be used before these topical medications and that hair should not be rewashed for 1–2 days after removing the medications. Along with these treatment options, heating clothing and linens to >50°C is also recommended for better efficacy.