Which condition is marked by progressive pelvic muscle weakness and wasting in male children, with tight heel cords?

The condition characterized by progressive pelvic muscle weakness and wasting in male children, along with tight heel cords, is Duchenne muscular dystrophy (DMD). This genetic disorder is caused by a mutation in the dystrophin gene, leading to muscle degeneration and weakness over time.

DMD primarily affects males due to its X-linked recessive inheritance pattern, which means that the condition is often expressed in young boys while females act as carriers with a lower likelihood of manifesting symptoms. The clinical presentation typically includes a gradual decline in muscle function, beginning with the pelvic girdle and progressing to other muscle groups. Additionally, individuals with DMD may develop tight heel cords, leading to contractures and mobility challenges.

The other conditions listed do not match this specific set of symptoms. Becker muscular dystrophy is similar to DMD but has a milder and later onset. Spinal muscular atrophy affects motor neurons and leads to muscle weakness but does not typically cause tight heel cords. Myasthenia gravis is an autoimmune disorder that results in fatigue and weakness but does not present with progressive muscle wasting in the same manner seen in DMD.