Scabies, lice and infestations — clinical case

Case

A 3-year-old boy from a remote community presents with a six-week history of intense itching that is worst at night and after a hot bath. His parents describe him scratching until the skin bleeds and waking the household repeatedly. Over the last fortnight his mother, father and older sister have all begun to itch, though none has visible lesions yet. The family lives in a crowded household with extended relatives. He is otherwise well, afebrile and thriving. [1]

Findings

On examination there are short, wavy, slightly raised serpiginous burrows in the finger-webs and on the flexor wrists, and excoriated inflammatory papules around the waist, umbilicus and genitalia. Several excoriated lesions carry honey-coloured crusting consistent with secondary impetigo. There are no thick hyperkeratotic crusts to suggest crusted scabies, and the palms, soles and scalp are clear. He meets the 2020 IACS criteria for clinical scabies: typical lesions in a typical distribution with itch and a clear epidemiological link to affected household contacts. [1]

Investigations

The diagnosis is clinical and does not require laboratory confirmation in this straightforward case. A skin scraping for mites, eggs or scybala is reserved for diagnostic uncertainty or suspected crusted scabies, neither of which applies here. Because the family lives in a remote community with a high burden of streptococcal skin disease, a urinalysis is performed to screen for haematuria and his blood pressure is checked, given the link between scabies-driven impetigo and acute post-streptococcal glomerulonephritis. [6]

Management

The boy is treated with permethrin five percent cream applied to the whole body from the neck down, including under the nails and in the finger-webs and genitalia, left on overnight for eight to fourteen hours, washed off, and repeated after seven to fourteen days. Crucially, every household member and close contact is treated on the same day, whether or not they itch, because the two-to-six-week incubation means the asymptomatic relatives are already infested. Linen, clothing and towels used in the previous two to three days are washed in a hot machine cycle, and items that cannot be washed are sealed in a bag for at least seventy-two hours. The impetiginised lesions are treated with an antistaphylococcal and antistreptococcal agent. [3]

Course

At two-week review the burrows and impetigo have settled and the family's itch has improved markedly, although the boy still itches somewhat. This is recognised as post-scabies itch, a hypersensitivity to residual mite antigen that can persist for several weeks after successful treatment, and the family is reassured that it is not evidence of failure or re-infestation. Because of the household's setting and the documented link between scabies and streptococcal skin disease, the family is linked to the community's Healthy Skin programme, which supports ongoing screening, environmental health measures and, where appropriate, mass drug administration with ivermectin to break community transmission. [6]