A 10-year-old boy presents with his mother, complaining of intense itching, worse at night, since the
first week of school. He has numerous excoriations in the interdigital web spaces, wrists, and anterior axillary folds. His infant sister has recently developed intensely pruritic linear lesions on her palms,
soles, face, and scalp. Their mother works in a nursing home and has developed pruritus and reddish-brown nodular lesions in her axillae and perineum that have persisted several months after she treated herself with a lotion that was provided at her place of work. As you exam the patient, your skin begins to itch.
Q 1, The most likely ectoparasite affecting this family is:
A) Head lice (pediculosis).
B) Chiggers (mites).
Answer And Discussion
The correct answer is “E.” Scabies.
Scabies’ mites (Sarcoptes scabiei) burrow into the epidermis, lay eggs, and hatch larvae in cycles of 3–4 days. The most notable clinical symptom is intense pruritus that is worse at night.
The typical lesion is small, erythematous, and papular and may resemble eczema in quality and distribution.
About 7% of individuals develop a nodular variant(like the mother in this case). Transmission is typically by direct contact and infestations may appear as epidemics in institutions like nursing homes. The organism may be spread by fomites as well, although to a lesser extent. Young children and infants often have involvement of palms, soles, face, and scalp. A clinical diagnosis may be made in the setting of pruritic rash, typical distribution, and multiple family members affected.
Q 2 What is the next best step in this case (the infant child weighs 10 kg)?
A) Removal of the individual organisms.
B) Tetracycline 10 mg/kg divided TID for all affected family members
C) Single-dose oral ivermectin 200 g/kg, repeated in 2 weeks for all affected family members.
D) Symptomatic treatment with topical steroids and oral antihistamines.
E) Single-dose oral ivermectin 200 g/kg repeated in 2 weeks for the mother; one application of 5%
permethrin cream for all other family members for 8–14 hours, followed by showering.
Answer And Discussion
The correct answer is “E.”
Permethrin cream is the topical medication of choice. Ivermectin, an antihelmintic medication, is indicated for adults with nodular disease (like the mother in this case), in epidemic settings, and for treatment of scabies crustosa.
Answer “B” is incorrect because tetracycline is not helpful in this situation and should be avoided in children.
Answer “C” is incorrect because oral ivermectin should be avoided in infants weighing <15 kg due to
concerns about increased penetration of the blood– brain barrier.
Finally, “D” is incorrect because scabies should be treated with specific therapy rather than simply symptomatic therapy.
All family members should be treated, regardless of the presence or lack of symptoms. Microscopic exam of a skin scraping may identify the mite but has poor sensitivity.
Other viable treatment alternatives include crotamiton 10% solution precipitated sulfur in petroleum and lindane (but avoid lindane in children <2 years old).