A 26-year-old female presents with a history of a rash of
two weeks duration. The rash has appeared on her lower legs, the lesions are
tender to touch.
She also gives a history of recurrent ulcers in her mouth
and she also says she has had recurrent episodes of diarrhoea and abdominal
pain and has lost some weight. No history of sore, throat, cough or
breathlessness. No history of genital ulceration.
She is a secretary, unmarried, does not take alcohol but
smokes 20 cigarettes a day.
On examination she looked underweight, there were several
tender, erythematous nodules over the anterior aspect of her lower legs. No
other abnormalities were detected.
Hb 12. 2 g/dL
WBC 12.9 x 10 9 /L
ESR 85 mm in 1st hour
In this patient which one of the following investigations
is likely to lead to a definitive diagnosis:
Serum angiotensin converting enzyme level
Slit skin smear