Diagnosis of all bullous conditions is based on three measures:
- Clinical features – appearance of lesions, erosions and blisters, Nikolsky sign, presence or absence of scarring and distribution of lesions.
- Biopsy of skin or mucous membrane, with characteristic histological features.
- Direct and indirect immunofluorescence – detection of autoantibodies either in a biopsy specimen (direct) or in the patient’s serum (indirect). Indirect (circulating) antibodies are helpful in confirming the diagnosis. The enzyme-linked immunoabsorbent assay (ELISA) is helpful for diagnosis, particularly if the immunofluorescence studies are negative, and to differentiate PV from PF; in the future newer more specific ELISAs hold promise as a prognostic indicator.
The following investigations are also recommended during disease assessment and management:
- Full blood count and differential
- Blood urea and electrolytes
- Liver function tests
- Blood glucose
- Antinuclear antibody (differential of pemphigus erythematosus)
- Thiopurine methyltransferase (TPMT) levels (if azathioprine is to be used)
- Chest X-ray
- Blood pressure
- Bone density scan (early in the course of treatment is recommended, and repeated periodically)
- G6PD and reticulocytes if dapsone is to be used
- Opthalmologic exam