The first symptoms normally occur in young adults (usually in their 20s or 30s). It is also possible to have an earlier or later onset of the condition, but that is rare. Initial signs of GNEM can include foot drop, which may lead to frequent tripping and difficulty in climbing stairs. Foot drop is dropping of the forefoot because of muscle weakness.
The severity and rate of progression are highly variable, even within families where more than one person is affected. The condition can worsen over time. As the condition progresses, it may lead to weakness in the upper leg muscles, leading to difficulty in climbing stairs or rising from a chair.
A person with GNEM may also eventually experience weakness in their hands and shoulder muscles. Quadriceps muscles, however, typically remain unaffected, even in late stages. People with GNEM generally experience increased disability and loss of ability to walk in later life.
The condition doesn’t usually affect the heart or respiratory muscles, or speech and swallowing.