Serial apneic attacks were noted during early infancy, and he developed infantile spasms by 1 year old. Abnormalities were identified on electroencephalography, and antiepileptic agents were administered. At 14-month old, he was referred to Tenshi Hospital for surgical treatment of a tumor developing in the sacrococcygeal region. At that time, serious psychomotor retardation was evident. He could not sit, turn over, or even suck milk. Distinctive dysmorphic features were evident, including prominent forehead, hypertelorism, shallow orbits, thick eyebrows, long eyelashes, depressed nasal root, upturned nostrils, low-set ears, hypospadias, right undescended testis, and overlapping fingers. Further examinations revealed atrophy of bilateral optic nerves, bilateral sensorineural deafness, broad ribs, and bilateral hydronephrosis (Fig. 1). The tumor was removed surgically at 16-month old, and histological analysis revealed malignant teratoma. DNA was extracted from peripheral lymphocytes, and the SETBP1 coding sequence was determined according to standard protocols. A heterozygous guanine-to-adenine missense mutation was found at position 2602, predicting an amino acid substitution (D868N). The patient died at 2 years and 9 months old due to generalized metastasis of malignant teratoma.