An inherited, congenital disorder resembling stiff-man syndrome is described in ten individuals from three generations of a family. The disease is apparently inherited as a dominant trait; x-linkage cannot be excluded. The diagnosis was based on the following criteria; (1) attacks of stiffness precipitated by surprise or minor physical contact; difficulty in sudden movements but absence of signs of myotonia or myokymia; (2) presence of the electromyographic counterpart of the stiffness, continuous activity at rest with normal action potentials; (3) disappearance of the continuous electrical activity after diazepam.
The symptoms were most marked in infancy, but ameliorated with time, becoming milder than in the average acquired case. The cause of this familial syndrome is presumably different from that or those of acquired, sporadic cases of stiff-man syndrome.
Klein R, Haddow JE, DeLuca C. Familial Congenital Disorder Resembling Stiff-Man Syndrome. Am J Dis Child. 1972;124(5):730-731. doi:10.1001/archpedi.1972.02110170108018