Prevalence and genetics of immotile-cilia syndrome and left-handedness

Immotile-cilia syndrome is characterized by severe respiratory distress from early infancy, and also often by situs inversus. The first description of the disease was based on just four persons, but reasons were given to suggest that the disorder may not be exceedingly rare. The purpose of the present study was to estimate just how rare or how common it is and to evaluate its association with situs inversus and with left-handedness. Data were mainly obtained from contacting a large number of Swedish clinicians who kindly informed us about their patients with suspected immotile-cilia syndrome. Diagnosis was in most cases performed by electron micro-scopical examination of nasal cilia or of spermatozoa. Based on these data, the prevalence of the syndrome in Sweden with or without situs inversus was estimated to be not far from 1 in 10,000. The syndrome consists of several subgroups that have a randomized determination of situs asymmetry (50% of these have situs inversus) and one subgroup in which situs inversus is not found. This results in a frequency of situs inversus in the syndrome of about 44%. Left-handedness is no more common than it is in healthy persons and no more often associated with situs inversus than with situs solitus. In all cases it is about 14%. It is concluded that the two major anatomical/physiological asymmetries of the human body are found with frequencies which indicate that they develop independently of each other. Both conditions appear with prevalences that may have changed at a secular scale, left-handedness with a substantial increase and situs inversus with a less dramatic increase.