Abstract The Klinefelter's syndrome (KS) is not a rare gonosomal aberration occurring in males. The disorder is characterized by microorchidism. Another typical although not constant symptom of this disorder is gynecomastia with almost normal male secondary sex characteristics. The etiology of the disease remains unexplained. Previous studies have shown that this disorder is a genetic chromosomal abnormality associated with the presence of one additional chromosome due to abnormal division. Thus, the affected individual has 47 chromosomes with the resulting chromosomal constellation of XXY (classical form) or 46,XY/47,XXX (mosaic form). Large population studies estimate the incidence of KS at 1:1000 live born male babies [Hammerton JL, Canning N, Ray M, et al. A cytogenic survey of 14,069 newborn infants. I. Incidence of chromosome abnormalities. Clin Genet 1975;8:223–243]. The locomotor apparatus of persons affected by the syndrome is characterized by acromicria, clinodactyly, concrescence of thoracal vertebral bodies and spinal osteoporosis in not only individuals of older age but also in younger persons. In 1960s and 1970s, reports were published on the concurrence of the KS with autoimmune diseases. The aim of our article is to discuss case reports on the KS published by authors from our institute as well as to present an overview of the reports published so far, mainly abroad.