Hello, I have read that some people with Kennedys disease sometimes get misdiagnosed with ALS. How can a neurologist differentiate these conditions? I understand there is a genetic test for Kennedys disease but what about the EMG? Will it have different readings for ALS or will the EMG readings be the same?

Thank you god bless.

Yes, ALS has been the most common misdiagnosis for those with KD. A couple dozen different causes have been identified for ALS with some having symptoms closer to KD, but in general ALS affects both upper and lower motor neurons while KD is considered primarily a lower motor neuron disease. Symptoms of upper motor neuron diseases include things like spasticity, muscle stiffness and hyper reflexes. KD commonly presents with signs of androgen insensitivity such as gynecomastia. ALS typically has a much faster progression of just a few years from onset to death so if someone has had gradually increasing symptoms for years before seeking diagnosis that would better fit KD than ALS. Genetic testing is now so widely available, inexpensive and accurate there is little reason to rely solely on clinical symptom diagnosis.