How does the incidence of myasthenia gravis (MG) vary by age?

Updated: Aug 27, 2018
  • Author: Abbas A Jowkar, MBBS; Chief Editor: Nicholas Lorenzo, MD, CPE, MHCM, FAAPL  more...
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MG can occur at any age. Female incidence peaks in the third decade of life, whereas male incidence peaks in the sixth or seventh decade. The mean age of onset is 28 years in females and 42 years in males.

Transient neonatal MG occurs in infants of myasthenic mothers who acquire anti-AChR antibodies via placental transfer of IgG. Some of these infants may suffer from transient neonatal myasthenia due to effects of these antibodies.

Most infants born to myasthenic mothers possess anti-AChR antibodies at birth, yet only 10-20% develop neonatal MG. This may be due to protective effects of alpha-fetoprotein, which inhibits binding of anti-AChR antibody to AChR. High maternal serum levels of AChR antibody may increase the chance of neonatal MG; thus, lowering the maternal serum titer during the antenatal period by means of plasmapheresis may be useful.

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