M 70, resident in a nursing home, extremely pruritic skin rash, trunk and legs.

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Diagnosis:
Scabies
Comment:

Scabies results from infestation by the mite Sarcoptes scabiei var. hominis. Skin rash results from an allergic  reaction to the mite, its egg or feces.

The rash occurs most commonly in the interdigital spaces, flexor surfaces of the wrist, axillae,waist,feet,and ankles.

Pruritus can be severe and is most prominent at night due to the mite being most active during this time.

Laboratory confirmation of the diagnosis is done by skin scrapings or biopsy to microscopically demonstrate the mite, its egg(s) or feces.

Histologically, the lesion caused by the mite is the burrow that it creates within the stratum corneum.

The irritative effect of the mite’s presence within the epidermis results in parakeratosis, spongiosis, vesiculation and eosinophilic infiltrates.

Visualization of the mite, its egg(s) or feces is needed for definitive diagnosis.