Database: thrombosis_prediction
Question: What percentage of male patients who first presented to the hospital in 1981 were diagnosed with BEHCET?
SQL: SELECT CAST(SUM(CASE WHEN Diagnosis = 'BEHCET' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(ID) FROM Patient WHERE STRFTIME('%Y', `First Date`) = '1981' AND SEX = 'M'