- Hyporeflexia (HP:0001265): Reduction of neurologic reflexes such as the knee-jerk reaction. Evidence: TAS. (OMIM:300376)
- Elevated circulating creatine kinase activity (HP:0003236): The activity of creatine kinase in the blood circulation is above the upper limit of normal. Evidence: TAS. (OMIM:300376)
- Abnormal EKG (HP:0003115): Abnormal rhythm of the heart. Evidence: IEA. (OMIM:300376)
- X-linked recessive inheritance (HP:0001419): A mode of inheritance that is observed for recessive traits related to a gene encoded on the X chromosome. In the context of medical genetics, X-linked recessive disorders manifest in males (who have one copy of the X chromosome and are thus hemizygotes), but generally not in female heterozygotes who have one mutant and one normal allele. Evidence: TAS. (OMIM:300376)
- Adult onset (HP:0003581): Onset of disease manifestations in adulthood, defined here as at the age of 16 years or later. Evidence: TAS. (OMIM:300376)
- Calf muscle pseudohypertrophy (HP:0003707): Enlargement of the muscles of the calf due to their replacement by connective tissue or fat. Evidence: TAS. (OMIM:300376)
- Muscular dystrophy (HP:0003560): The term dystrophy means abnormal growth. However, muscular dystrophy is used to describe primary myopathies with a genetic basis and a progressive course characterized by progressive skeletal muscle weakness and wasting, defects in muscle proteins, and histological features of muscle fiber degeneration (necrosis) and regeneration. If possible, it is preferred to use other HPO terms to describe the precise phenotypic abnormalities. Evidence: IEA. (OMIM:300376)
- Cardiomyopathy (HP:0001638): A myocardial disorder in which the heart muscle is structurally and functionally abnormal, in the absence of coronary artery disease, hypertension, valvular disease and congenital heart disease sufficient to cause the observed myocardial abnormality. Evidence: TAS. Onset: Late onset (HP:0003584). (OMIM:300376)
- Arrhythmia (HP:0011675): Any cardiac rhythm other than the normal sinus rhythm. Such a rhythm may be either of sinus or ectopic origin and either regular or irregular. An arrhythmia may be due to a disturbance in impulse formation or conduction or both. Evidence: TAS. (OMIM:300376)
- Muscle weakness (HP:0001324): Reduced strength of muscles. Evidence: TAS. (OMIM:300376)
- Myalgia (HP:0003326): Pain in muscle. Evidence: TAS. (OMIM:300376)
These phenotypes are associated with the disease Becker muscular dystrophy (OMIM:300376).