instruction: among patients diagnosed with wegener's granulomatosis, how many of them received sl therapy?
response: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN diagnoses ON demographic.hadm_id = diagnoses.hadm_id INNER JOIN prescriptions ON demographic.hadm_id = prescriptions.hadm_id WHERE diagnoses.short_title = "Wegener's granulomatosis" AND prescriptions.route = "SL"