What are the key clinical features to differentiate between Duchenne and Becker muscular dystrophy in a child presenting with muscle weakness?

Differentiating between Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) in a child presenting with muscle weakness primarily relies on the age of onset, rate of disease progression, and overall severity of symptoms, although both are inherited neuromuscular disorders Menezes & North 2012.

• Age of Onset: Duchenne muscular dystrophy typically presents earlier, often between 2 and 3 years of age, whereas Becker muscular dystrophy usually has a later onset, frequently in late childhood or adolescence Orrell 2012.
• Disease Progression and Severity: DMD is characterised by a more rapid and severe progression, often leading to loss of ambulation by early teenage years. In contrast, BMD has a slower, more variable course, with individuals often retaining the ability to walk into adulthood Orrell 2012Piga et al. 2019.
• Clinical Manifestations: While both conditions involve progressive muscle weakness, often starting in the proximal muscles, and can present with features such as Gowers' sign and pseudohypertrophy of the calves, these manifestations are typically more pronounced and appear earlier in DMD Orrell 2012.
• Cardiac Involvement: Both DMD and BMD can lead to significant cardiac involvement, which is a major cause of morbidity and mortality. However, cardiac complications often present earlier and are generally more severe in DMD Orrell 2012Piga et al. 2019.
• Prognosis and Life Expectancy: The prognosis for DMD is significantly poorer, with a reduced life expectancy often into the 20s. Patients with BMD generally have a longer life expectancy, often reaching middle age or beyond, though this can vary Orrell 2012.

For any child presenting with suspected neurological conditions, including progressive muscle weakness, prompt recognition and referral to a specialist are crucial for accurate diagnosis and management NICE NG127.