Professor Akinyanju is the founder and chairman of the board of directors of the Sickle Cell Foundation Nigeria. He is an alumnus of St Mary's Hospital Medical School now known as the Imperial College of Science Technology and Medicine of the University of London from where he qualified with the degrees MB BS in 1963. He did his internship and training in internal medicine in Britain and returned to Nigeria in 1967 where he joined the staff of the Lagos University Teaching Hospital (LUTH) and soon afterwards, the College of Medicine of the University of Lagos. He left to undertake a Fellowship in Haematology at the University of Toronto from 1970 to 1972.

On returning, he created a separate Sickle Cell Clinic in LUTH and he was appointed a Professor of Medicine in 1979 and soon afterwards head of the department of Medicine. He earned the higher degree of Doctor of Medicine of the University of London and he is a Fellow of the Royal Colleges of London and of Edinburgh and of the American College of Physicians, the West African College of Physicians and the Nigerian Postgraduate Medical College in the faculties of Internal Medicine and of Pathology. He was appointed in1982 and still serves as Medical Advisor to the American Embassy in Lagos. From 1985 he has been an Honorary Adviser to the Hereditary Disease Programme of the World Health Organisation.

He also served in 1998 as a consultant on sickle cell disorder to the Wellcome Trust in London. He resuscitated the Sickle Cell Clubs in Nigeria starting with Lagos in1984. In 1991 he founded the Federation of Sickle Cell Clubs of Nigeria and in 1994 the Sickle Cell Foundation Nigeria. In 1986 he pioneered the training in counselling on sickle cell disorder in Nigeria and in 1993 the training of locally resident obstetricians in chorionic villus sampling, following which, prenatal diagnosis of sickle cell disorder was introduced as a service in Nigeria.

In 1995 he initiated the formation of a pan African Federation of Associations on Sickle Cell Disorders in Africa of which he is now Executive Secretary. He is a past President of the Nigerian Society of Haematology and Blood Transfusion and a past President of the Association of Physicians of Nigeria. He is the author of numerous publications in medical and scientific journals and books and he has delivered numerous papers and lectures on sickle cell disorder in several countries.