This is a rash that is difficult to diagnose clinically
unless you include it in your differential diagnoses of a groin or genital
rash. It looks red and scaly like a psoriasis
or crusted as in impetigo or Hailey Hailey disease. However this is extramammary
Paget’s disease where tumour cells are confined to the epidermis. These cells
can arise from an underlying apocrine
gland tumour or from an adjacent carcinoma such as bladder, prostate or rectum.
A punch skin biopsy can differentiate. A tinea infection should show central
clearing with a spreading scaly edge. This patient has been treated over 10
years with combinations of topical Imiquimod, efudix, PDT and cryotherapy with
partial clearing in the pale area above. The rash is often multifocal making
surgical excision difficult. This patient has not shown any evidence of an
underlying internal organ malignancy. At present it is being treated with
Imiquimod topically and cryotherapy. See www.skinconsult.com.au
for other images.
