Rapsyn mutations in hereditary myasthenia: distinct early- and late-onset phenotypes.
Burke G., Cossins J., Maxwell S., Owens G., Vincent A., Robb S., Nicolle M., Hilton-Jones D., Newsom-Davis J., Palace J., Beeson D.
Rapsyn mutations in 16 unrelated patients with a congenital/hereditary myasthenic syndrome were identified, and a mutation (N88K) common to each of them was found. Two distinct phenotypes were noted: early and late onset. The former is frequently associated with arthrogryposis multiplex congenita and life-threatening crises. The late-onset phenotype developed in adolescence or adulthood and was initially mistaken for seronegative myasthenia gravis. Recognition of this late-onset phenotype should prevent inappropriate immunotherapy.