A 24-year-old man presents with pruritus in the pubic region. Examination reveals small brownish-grey insects firmly attached to pubic hair with nits cemented to hair shafts. Similar involvement of the eyelashes is noted. The causative organism is:
- A Sarcoptes scabiei var. hominis
- B Phthirus pubis ✓
- C Pediculus humanus capitis
- D Demodex folliculorum
Correct answer: B. Phthirus pubis
Explanation
Phthirus pubis (crab louse) characteristically infests coarse body hair including pubic hair, axillary hair, and can involve eyelashes and eyebrows. The insect appears broader and shorter than head lice, resembling a crab. Pediculus humanus capitis infests scalp hair. Sarcoptes scabiei causes scabies with burrows, not visible insects attached to hair.
Reference: Rook's Textbook of Dermatology, 9th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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