**Question:** All are Congenital Myopathies, Except:

A. Facio-scapulo-humeral dystrophy (FSHD)
B. Emery-Dreifuss muscular dystrophy (EDMD)
C. Muscular dystrophy
D. Myotonic dystrophy

**Core Concept:** Congenital myopathies are a group of inherited neuromuscular disorders characterized by muscle weakness and wasting starting in infancy or early childhood. These conditions are due to defects in proteins involved in muscle structure, function, or maintenance. Muscle biopsies typically show abnormal fibers with rimmed vacuoles, central nuclei, and giant sarcomeres.

**Why the Correct Answer is Right:**

Duchenne and Becker muscular dystrophies are X-linked recessive disorders affecting primarily boys. They are caused by mutations in the DMD gene, which encodes dystrophin, a cytoskeletal protein essential for maintaining muscle structure and function. Unlike congenital myopathies, these dystrophies present later in childhood or adolescence, often with progressive limb girdle weakness and cardiac involvement.

**Why Each Wrong Option is Incorrect:**

A. Facio-scapulo-humeral dystrophy (FSHD) is a type of autosomal dominant myopathy characterized by weakness and wasting of the muscles involving the face, shoulder girdle, and upper arms. It is caused by mutations in the DNM2 gene, encoding the protein dynamin 2, which plays a role in vesicle trafficking and endocytosis within muscle cells.

B. Emery-Dreifuss muscular dystrophy (EDMD) is a group of autosomal dominant or recessive disorders characterized by progressive muscular dystrophy affecting the skeletal muscles and heart. It is caused by mutations in genes like EMD, LMNA, or SYNE1, which encode proteins essential for maintaining the nuclear envelope, intermediate filaments, and nuclear envelope components, respectively. EDMD presents later than congenital myopathies, typically in teenage years or early adulthood.

C. Myotonic dystrophy is a group of autosomal dominant disorders characterized by slow muscle weakness and wasting, myotonia (muscle stiffness on passive stretch), and cataracts in later life. It is caused by mutations in the DMWD gene, encoding the protein dystrophin, which plays a role in maintaining muscle structure and function. Myotonic dystrophy presents at an older age than congenital myopathies and has distinct clinical features unrelated to congenital myopathies.

Duchenne and Becker muscular dystrophies are X-linked recessive disorders affecting primarily boys, whereas congenital myopathies affect infants and children. Congenital myopathies are characterized by a more rapid progression of muscle weakness and wasting, distinct clinical features (e.g., respiratory muscle involvement), and a genetic basis distinct from dystrophies. The correct answer, Duchenne muscular dystrophy, is caused by mutations in the DMD gene, encoding dystrophin, which is essential for maintaining muscle structure and function.

**Core Concept:** Dystroph