Fatigable weakness

What it means

A type of weakness that occurs after a muscle group is used and lessens if the muscle group has some rest. That is, there is diminution of strength with repetitive muscle actions.

This type of weakness is pathognomonic for an abnormality of the neuromuscular junction such as myasthenia gravis. A characteristic form of muscular weakness that worsens after use of affected muscles. Myasthenia is caused by failure of neuromuscular transmission, which results from the binding of autoantibodies to proteins involved in signaling at the neuromuscular junction, including especially the nicotinic acetyl choline receptor (AChR) or, less frequently, a muscle-specific tyrosine kinase involved in AChR clustering.

Rare diseases that can present with this16

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category

Also called: Fatigable weakness of limb muscles · Generalised muscle weakness due to defect at the neuromuscular junction · Generalized muscle weakness due to defect at the neuromuscular junction · Myasthenia · Myasthenic weakness · Proximal muscle weakness due to defect at the neuromuscular junction