Clinical Guidance

Males

The dystrophinopathies cover a spectrum of muscle disease that ranges from mild to severe. The mild end of the spectrum includes the phenotypes of asymptomatic increase in serum concentration of creatine phosphokinase (CK) and muscle cramps with myoglobinuria. The severe end of the spectrum includes progressive muscle diseases that are classified as Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) when skeletal muscle is primarily affected and as DMD-associated dilated cardiomyopathy (DCM) when the heart is primarily affected . DMD vs BMD vs DMD-associated DCM. The distinction between DMD and BMD is based on the age of wheelchair dependency: before age 13 years in DMD and after age 16 years in BMD.

Diagnostic Criteria

The dystrophinopathies cover a spectrum of X-linked muscle disease that ranges from mild to severe and includes Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD), and DMD-associated dilated cardiomyopathy (DCM). Suggestive Findings A dystrophinopathy should be suspected in an individual with the following and findings that support the diagnosis of DMD, BMD, or DMD-associated DCM – especially when they occur in addition to a positive family history compatible with X-linked inheritance. Findings are most commonly noted in males, but females may also be affected. Clinical Findings Duchenne muscular dystrophy (DMD) • Progressive symmetric muscle weakness (proximal distal) often with calf hypertrophy • Symptoms present before age five years • Wheelchair dependency before age 13 years Becker muscular dystrophy (BMD) • Progressive symmetric muscle weakness (proximal distal) often with calf hypertrophy; weakness of quadriceps femoris in some cases the only sign • Activity-induced cramping (present in some individuals) • Flexion contractures of the elbows (if present, late in the course) • Wheelchair dependency (after age 16 years); although some individuals remain ambulatory into their 30s and in rare cases into their 40s and beyond • Preservation of neck flexor muscle strength (differentiates BMD from DMD) Note: The presence of fasciculations or loss of sensory modalities excludes a suspected diagnosis of a dystrophinopathy. Individuals with an intermediate phenotype (outliers) have symptoms of intermediate severity and become wheelchair dependent between ages 13 and 16 years. DMD-associated dilated cardiomyopathy (DCM) • DCM with congestive heart failure, with males typically presenting between ages 20 and 40 years and females presenting later in life • Usually no clinical evidence of skeletal muscle disease; may be classified as "subclinical" BMD • Rapid progression to death in several years in males and slower progression over a decade or more in females See also Dilated Cardiomyopathy Overview. Laboratory Testing Serum creatine phosphokinase (CK) concentration. See . Table 1. Serum Creatine Phosphokinase (CK) Concentration in the Dystrophinopathies

Management Guidelines

Evaluations Following Initial Diagnosis

To establish the extent of disease and needs in an individual diagnosed with a dystrophinopathy, the following evaluations are recommended if they have not already been completed:

Surveillance Guidelines

Cardiac

The American Academy of Pediatrics (AAP) has published recommendations for optimal cardiac care in persons with dystrophinopathy (full text) and consensus guidelines .

DMD

• Complete cardiac evaluation at least every two years, beginning at the time of diagnosis