pseudohypertrophic

Pseudohypertrophic refers to the apparent enlargement of a body part that results from the replacement of muscle tissue with fat and connective tissue, rather than true enlargement of muscle fibers (hypertrophy). In medical contexts, it most often describes the enlarged calf muscles seen in certain muscular dystrophies, where outward size does not correspond to functional strength.

The term is most commonly associated with dystrophic conditions such as Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD). In these disorders, progressive loss of muscle fibers is followed by infiltration of fat and fibrous tissue, leading to a visibly swollen or firm calf with relatively weak muscles. Pseudohypertrophy can also occur in other neuromuscular or metabolic conditions, though less characteristically.

Pathophysiology involves chronic muscle fiber necrosis and degeneration, with subsequent replacement by adipose tissue and connective tissue. This process reduces muscle strength and functional capacity, even as the limb appearance becomes larger. Clinically, patients may have difficulty with activities requiring leg strength, along with signs such as Gowers' sign in childhood. Calf pseudohypertrophy is a classic finding in DMD.

Diagnosis combines clinical examination with laboratory and genetic testing. Serum creatine kinase levels are often elevated. Genetic testing can identify mutations in the dystrophin gene (DMD) or related genes in BMD. Muscle biopsy and imaging (MRI) may show fatty infiltration and fibrous replacement of muscle tissue, supporting the diagnosis and helping to distinguish from true muscular hypertrophy.

Management focuses on multidisciplinary care, including physical therapy, respiratory support as needed, orthopedic management, and, in some cases, disease-modifying therapies. Prognosis varies by underlying condition and severity, but pseudohypertrophy typically reflects progressive neuromuscular decline rather than increased functional capacity.