We report a 73-year-old Japanese woman with familial Parkinson's disease. The patient was well until her 67 years of the age, when she noted rest tremor in her right hand. Soon after her gait became short stepped. She visited our clinic on October 6, 1992 when she was 68 years old. She was alert and well oriented without dementia. She showed masked face, small voice, small stepped gait, retropulsion, resting tremor in her right hand, rigidity in the neck, and bradykinesia. She was treated with 400 mg/day of levodopa-carbidopa, which improved her symptoms, however, she developed wearing off phenomenon 3 years after the initiation of levodopa treatment. On August 26, 1998, she developed abdominal pain, diarrhea, and vomiting. She was admitted to another hospital, where abdominal plain x-ray revealed an evidence of intestinal obstruction (ileus). She was treated with nasogastric suction and intravenous fluid. Her condition did not improve and she was transferred to our hospital on August 29, 1998. Her family history revealed no consanguineous marriage. She had two elder brothers and three elder sisters. One of her brothers had been diagnosed as Parkinson's disease. Her husband also suffered from Parkinson's disease, however, her parents apparently did not have Parkinson's disease. On admission, she appeared to be drowsy. Her blood pressure was 102/70 mmHg, body temperature 36.2 degrees C. The lungs were clear and no cardiac murmur was present. Abdomen was flat and bowel sound was audible. No abnormal mass was palpable. Neurologic examination revealed mild consciousness disturbance, masked face, and small voice. No motor paralysis was noted. Muscle tone was hypotonic. No abnormal involuntary movement was noted. Abnormal laboratory findings on admission were as follows; WBC 11,300/microliter, amylase 1,373 IU/l, CK 446 IU/l, BUN 50 mg/dl, creatinine 1.17 mg/dl, CRP 22.7 mg/ dl, Na 134 mEq/l, K 3.1 mEq/l, and Cl 81 mEq/l. A chest x-ray film revealed pneumonic shadows in both lower lung fields. She was treated by nasointestinal suction, intravenous fluids, and chemotherapy for her infection. Her BP started to drop on September 2 and she developed cardiac arrest on the same day. She was discussed in a neurological CPC. The chief discussant arrived at the conclusion that the patient had a form of autosomal dominant familial Parkinson's disease. As parents did not have Parkinson's disease, some of the participants raised the possibility of autosomal recessive inheritance. But the age of onset was too late for autosomal recessive inheritance. Majority thought that the mode of inheritance was autosomal dominant with low penetrance. alpha-Synuclein mutation causes an autosomal dominant familial Parkinson's disease, but this type is very rare in non-Greek populations and the penetrance is high. Chromosome 2-linked autosomal dominant familial Parkinson's disease shows low penetrance. There are many other autosomal dominant forms of familial Parkinson's disease linked to yet unknown chromosome loci. Majority thought that this patient also had a form of Lewy-body positive autosomal dominant familial Parkinson's disease of unknown chromosome locus. Post mortem examination revealed ischemic intestinal lesion with strangulation. This was thought to be the cause of her death. In the central nervous system, the brain appeared to be normal by inspection. In the coronal sections, the substantia nigra and the locus coeruleus showed marked depigmentation. Histologic examination revealed marked neuronal loss and Lewy body formation in the remaining neurons. Pathologic examination was consistent with Parkinson's disease. Mutational analysis for the parkin gene was negative.