What is the difference between true muscle hypertrophy and pseudohypertrophy?

In the context of muscle pathology, the distinction between true muscle hypertrophy and pseudohypertrophy lies in the composition of the enlarged tissue.

• True muscle hypertrophy refers to an actual increase in the size of muscle fibers. This occurs naturally in athletes through exercise, which stimulates muscle growth and adaptation to physical loads. In certain rare conditions, such as myotonia congenita, hypertrophy can also occur as a pathological increase in muscle size accompanied by strength and stiffness.12
• Pseudohypertrophy is a condition where the apparent enlargement of a muscle is not caused by an increase in muscle fiber mass. Instead, it results from the deposition of fat and connective tissue within the muscle. This is a characteristic feature of several forms of muscular dystrophy, most notably the Duchenne type.1

While true hypertrophy involves the growth of functional muscle tissue, pseudohypertrophy represents a replacement of muscle substance with non-contractile tissue, which does not contribute to muscle strength.1