**Question:** An eight-year-old boy presents with multiple umbilicated papules on the trunk. Diagnosis is –

A. Impetigo
B. Eczema
C. Pediculosis
D. Scabies

**Correct Answer:** D. Scabies

**Core Concept:** Umbilicated papules on the trunk in an eight-year-old boy can be indicative of various dermatological conditions. Scabies is a common skin infection caused by the mite Sarcoptes scabiei, which primarily affects the skin, particularly in immunocompromised individuals or those with close contact with infected individuals.

**Why the Correct Answer is Right:** Scabies is caused by the parasitic mite Sarcoptes scabiei, which burrows into the skin and causes an inflammatory response, leading to the formation of papules, which become umbilicated due to the mite burrowing and feeding inside the skin. The key feature of scabies is the presence of these umbilicated papules, which is why we can confidently choose option D as the correct answer.

**Why Each Wrong Option is Incorrect:**

A. Impetigo: Impetigo is an infection caused by bacteria (usually Streptococcus or Staphylococcus species) and presents with superficial, vesicular lesions rather than umbilicated papules.

B. Eczema: Eczema is a group of skin conditions characterized by dry, itchy, and inflamed skin. It is not specific to umbilicated papules and can be found on any part of the body, not just the trunk.

C. Pediculosis: Pediculosis is an infestation with head lice or body lice, not caused by a mite. The clinical presentation would differ significantly, with lice infestation presenting with pruritus (itching) and hair loss in the head lice case, or with pruritus (itching) and alopecia (hair loss) in the body lice case.

**Clinical Pearl:** Scabies is a common skin infection that can be diagnosed clinically based on the umbilicated papules and the patient's history of close contact with another infected individual. Treatment typically involves the use of topical or oral anti-parasitic medications, such as permethrin or ivermectin, along with appropriate measures for close contacts to prevent further transmission.