Professor Tadashi Kajii, an honorary member of the Japan Society of Human Genetics (JSHG) and emeritus professor of Yamaguchi University, sadly passed away on 1 February 2016 at the age of 86 years.

Tadashi Kajii was born in Tokyo on 31 July 1929 to Sadayoshi and Sadako, the second-eldest boy of three brothers and four sisters. He enrolled in Hokkaido Imperial University School of Medicine in 1946. After graduation in 1953, he trained in pediatrics at Hokkaido University School of Medicine, obtaining his doctorate on the theme of ‘quantitative analysis of glycogen in neutrophils’ in 1959. In October 1961 he was appointed as lecturer of pediatrics at Hokkaido University, and specialized in the newly arising field of clinical dysmorphology as one of its pioneers in Japan. Shortly thereafter, in January 1962, he read a paper written by German pediatrician W. Lenz, which suggested a link between phocomelia and thalidomide intake. This prompted Kajii to survey phocomelia in Japanese infants. He soon found a correlation between thalidomide intake during pregnancy and phocomelia in seven infants, and reported his findings in July 1962. He continued to vigorously pursue efforts to publish his thalidomide research. In September 1962, thalidomide was withdrawn in Japan. One cannot understate his contribution to the prevention of birth defects in infants through his highly reliable data.

Kajii moved to the Department of Pediatrics at New York State University, Syracuse as a visiting scientist in 1966, where he studied clinical cytogenetics in Lytt I. Gardner’s laboratory. During his 18-month stay he described new syndromes and chromosome abnormalities in the literature on a weekly basis, which included Neu–Laxova syndrome and 4p- syndrome.

After returning to Japan in 1967, he resigned from Hokkaido University and in 1969 became an associate professor of the Department of Obstetrics and Gynecology at Geneva University. Here he performed pioneering work on the cytogenetics of spontaneous abortuses with his colleague, Dr Koso Ohama, and discovered the androgenetic origin of hydatidiform mole and the dispermic origin of XY hydatidiform mole. For his research achievements on complete moles he was awarded the JSHG Prize in 1985.

He moved again to New York State University in Syracuse in 1976, before being appointed as a professor of the Department of Pediatrics at the Yamaguchi University School of Medicine in 1978, where he expanded his research in the field of pediatrics and fostered young doctors. After retiring from Yamaguchi University in 1993, Kajii worked as a special advisor of SRL Inc. and studied a number of rare congenital disorders, including premature chromatid separation (PCS) syndrome, continuing to contribute to the identification of underlying genes and elucidation of their functions.

Kajii contributed widely to social activity. He was called as a witness in court by the plaintiff for the thalidomide cases in 1971, hosted the international symposium on oral contraceptive effects on the human fetus in Geneva in 1972 and was a member of the Committee of the Human Frontier Science Program Feasibility Study in 1987.

He made extensive contributions to the academic world, especially with the JSHG. Kajii was one of the founding members of the scientific meeting ‘Dysmorphology Night’, which is still organized annually. He was the first chairperson of the Board Certification Committee of the JSHG. Along with Drs Yoshikazu Kuroki and Norio Niikawa, in 1990 he published the 'Atlas of Congenital Malformation Syndromes', compiled on the basis of dysmorphic disorders among Japanese patients. He organized the 36th Annual Meeting of the JSHG in Yamaguchi in 1991, and established a Japanese-language internet website, ‘If you find chromosome abnormality’ (http://www.cytogen.jp/index/index.html), to gain a better understanding of chromosome analysis, which, since its inception in 2004, has welcomed over 200 000 visitors. He also gave lectures on scientific writing to young medical geneticists. Professor Kajii was thus not only a great scientist, but also an inspiring teacher and mentor.

Professor Kajii devoted his life to human genetics research. His memory and legacy will remain forever etched in our minds. We convey our deepest sympathy and heartfelt condolences to his wife Hisako and family members.