thomsen's disease

from The Century Dictionary.

• noun An affection characterized by inability to relax at once certain groups of muscles that have been contracted after a period of rest. It runs in families, beginning very early in life. Also called myotonia congenita.

from the GNU version of the Collaborative International Dictionary of English.

• (Med.) An affection apparently congenital, consisting in tonic contraction and stiffness of the voluntary muscles occurring after a period of muscular inaction.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a mild, rare, congenital form of myotonia characterized by muscle stiffness