• We describe a family with classic features of continuous muscle fiber activity (Isaacs-Mertens syndrome) appearing in an autosomal dominant pattern. Both a mother and her son had muscle stiffness and rigidity in early childhood. Because the mother's condition was not immediately apparent, we recommend a thorough examination of family members.
McGuire SA, Tomasovic JJ, Ackerman N. Hereditary Continuous Muscle Fiber Activity. Arch Neurol. 1984;41(4):395–396. doi:10.1001/archneur.1984.04050160057016