Another in the series of not quite what it looks. These are
crusts, excoriations and erosions. You might think the likeliest diagnosis
would be an infected dermatitis. However your swabs for bacterial culture come
back negative and the oral antibiotics have not improved things either. Crusts
usually arise from blistering, infected disorders and staph infected eczema is
certainly a common cause. However in the elderly, if crusts are also seen on
the back and trunk and there is oral ulceration, consider the rarer blistering
disease of Pemphigus. This lady did not have oral ulceration but there is a
variant of pemphigus called pemphigus foliaceous where the split is high up in
the epidermis under the stratum corneum and blisters hardly have time to form
before becoming crusts. The
intercellular protein attacked in pemphigus foliaceous does not occur in the
mouth so no oral ulcers are seen but the opposite is true in pemphigus vulgaris
where oral ulceration is often the presenting feature. She needs a skin biopsy
with immunofluorescence and oral steroids and a steroid sparing agent in the
longer term to control her autoimmune disease.
