We report a case of a patient with anti PL-12 antibody accompanied by interstitial pneumonia and severe pulmonary hypertension. At first presentation, hyperkeratotic skin lesions were found, although the diagnosis of CVD was not conclusive. Lung histology showed diffuse fibrosing interstitial pneumonia predominantly in the subpleural regions. During the seven-year follow-up period, severe pulmonary hypertension developed, although the progression of lung fibrosis was relatively limited. Anti-PL12 antibody was detected, and therefore the patient was diagnosed as having antisynthetase syndrome. Lung histology and pulmonary arteriogram suggested that vascular involvement of the disease contributed to the development of severe pulmonary hypertension.