A burrow on the side of the finger near the web space.

SCABIES

Scabies is the infestation of the skin by the scabies mite. Intense itching caused an allergic contact dermatitis to the mite, its eggs and feces ensues.

• Oral ivermectin once and then repeated had the highest success rate of treatment (93%) in one recent meta review.
• Do not treat any itchy rash as scabies until the diagnosis is confirmed by either finding classic burrows or seeing the mite with a skin scraping.
• Treat not just the patient but the family/girlfriend/boyfriend as well.
• When using permethrin cream, the patient and family needs to show good technique. If anyone misses one square inch, e.g., on the back or one toe web, the rash and itch can all come back.
• Give a topical steroid as well. The itch will last 1-2 weeks even after treatment. "Dead bug parts," of which the patient is allergic, are still on the skin for 1-2 weeks until shed.
• The patient with scabies for the first time has 10-12 mites total. If has had before (and thus immunity) only 5-6 mites.
  

The patient presents with intense itching. It is often worse at night, but this may be because there is nothing to distract the patient from the itch. Other members of the family are often affected. The best place to see the burrows, which appear as 3-10 mm thread-like lines, is between the fingers in the web spaces and along the sides of the feet. Red papules on the penis are classic and are highly suggestive. Diffuse itching and red 2-4 mm bumps on the penis are almost always scabies.

Crusted scabies is a severe and highly contagious form of scabies in which thousands of mites trigger diffuse crusting and even thick, hyperkeratotic plaques.

Diagnosis

For the experienced clinician, seeing even one classic burrow establishes the diagnosis. In uncertain cases or in order to confirm the diagnosis, dermoscopy is used by many dermatologists. In typical cases, burrows may be readily identified. At 20-40 magnification, the mite's head and 2 pairs of forelegs resemble the triangular shape of a hang-glider. Sometimes the contour of the round body of the mite can also be identified. The adhesive tape test is convenient and a valuable screening tool. For that, strips of tape are applied to areas suspected of being burrows and then rapidly pulled off. These are then applied to microscope slides and examined. Finally, a KOH or mineral oil examination may be done. Suspected burrows and itchy papules are scraped with a mineral oil-coated blade. The material is applied to a slide, oil added and examined microscopically.

Burrows on the wrist

Crusted Scabies

Scabies of the penis. Red macules and papules are seen. A burrow may be visible atop a papule.

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