High rate of twins among offspring of mothers with the Järvi-Hakola-Nasu disease and with comments on disorders associated with twinning.

Finnish mothers with Jrvi-Hakola-Nasu disease, progressive dementia with lipomembranous polycystic osteodysplasia (McKusick 221770) have a high rate of twin maternities, 128.2/1000. The exact 99% confidence intervals are 28.7-322.2/1000, thus above the average twinning rate in Finland, i.e. 15/1000. This eightfold increase in twinning may be an indication of a disturbed cortico-hypothalmic-hypophyseal axis or an other premorbid hormonal imbalance. It is concluded that even if dizygotic twinning is as a rule an event in itself, not only iatrogenic factors, as ovulation inducers, etc., but also some genetic disorders may be associated with twinning. More studies are needed to elucidate the incidence of twinning in families with these disorders.