Answer to Image of the Month November 2013

Submitted by M Ramam, Manoj Singh



Within the stratum corneum of an acanthotic epidermis, cross sections of two scabies mites, Sarcoptes scabei can be seen.

The total number of mites found in the entire skin of a patient with scabies is about 10-15, far fewer than the number of papules and pustules seen. For a single biopsy to show 2 mites is unusual and indicates that the patient has an extensive infestation referred to as crusted scabies or Norwegian scabies.

In this variant of the disease, there is a widespread, scaly and crusted eruption affecting large areas of the skin. Skin lesions teem with mites but as they bear little resemblance to the usual presentation of scabies, the clinical diagnosis is often missed (see image below).

Dermatologists do not usually biopsy ordinary scabies but biopsies of unsuspected crusted scabies are likely to be sent with clinical differential diagnoses of erythroderma or extensive endogenous dermatitis. Careful examination of the biopsy will lead to the diagnosis as the mite is readily recognized but it is easy to overlook findings in the stratum corneum if one is looking for features that are suggested by the clinical diagnoses.


crusted scabiesExtensive crusted scabies resembling erythroderma