“An Extended Family With a Dominantly Inherited Speech Disorder”, J. A. Hurst, M. Baraitser, E. Auger, F. Graham, S. Norell1990-04-01 (rare mutations, natural selection, IQ, language)⁠:

A three-generation family is described in which 16 members have a severe developmental verbal dyspraxia. Inheritance is autosomal dominant [disruption of FOXP2], with full penetrance.

Intelligence and hearing are normal.