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Early diagnosis of Duchenne muscular dystrophy is essential to improve long term outcomes
  1. Ros Quinlivan
  1. Correspondence to Dr Ros Quinlivan, MRC Centre for Neuromuscular Disease, National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK; Dubowitz Neuomuscular Centre, Great Ormond Street Hospital, London WC1; r.quinlivan{at}ucl.ac.uk

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In this issue, van Reiten et al1 demonstrate significant delays in the diagnosis of Duchenne muscular dystrophy (DMD), which may have a significant impact on clinical management. They argue that screening for DMD should be part of the routine 2-year developmental check.1 DMD is the most common and one of the most devastating disorders of skeletal muscle. Without treatment, the condition has a rapidly progressive course resulting in the loss of ambulation in the first decade and death in the late teens. In recent years, improvement in management has led to substantial improvements in life expectancy. From 1960 onwards, the development of specialist multi-disciplinary clinics improved mean life expectancy from 14 to 18 years. This was probably due to physical therapies for reducing contractures delaying the loss of ambulation, since the age at which ambulation is lost appears to correlate with long term life expectancy. The introduction of nocturnal non-invasive home ventilation (NIV) in the early 1990s led to a further improvement in mean survival to the late 20s. Additional data showed that scoliosis surgery had an added benefit on survival, with those patients who had both NIV and scoliosis surgery surviving into their mid-30s.2 Furthermore, early cardiac treatment with ACE inhibitors and beta blockers have been shown to delay the progression of dilated cardiomyopathy. Survival data from retrospective cohort studies show that adults with DMD managed in this way can survive to their mid-40s.3

Within the last 10 years, corticosteroid treatment was introduced following evidence from randomised controlled trials which showed that the rate of deterioration in functional skills was slowed but they did not evaluate the risk to benefit ratio for daily versus intermittent dosing. A longitudinal UK audit produced and published by the ‘North Star Network’ demonstrated significant beneficial effects of both daily and intermittent corticosteroids, the most important of which was prolongation of independent ambulation. However, the long term side effects associated with daily corticosteroid treatment were greater than intermittent steroids.4 Furthermore, data from this audit suggest that those boys who start corticosteroids at an earlier age (less than 5 years) have a predicted better outcome, while initiating corticosteroids after the age of 7 years has reduced efficacy. Thus, there is a ‘window of opportunity’ for starting corticosteroids. Long term cohort studies also suggest that corticosteroid treatment has a protective effect on both cardiac and respiratory function over time.5 There now exists a National Institute of Health and Care Excellence accredited guideline of the management of DMD, but for best clinical outcomes early diagnosis is very important.

van Reiten et al highlight the fact that delayed diagnosis has been a persistent issue over the last 30 years with little if any improvement in the age at which boys are diagnosed.1 In order to identify where these delays occurred, they retrospectively reviewed hospital notes of boys diagnosed with DMD in the last 10 years; all patients were attending a specialist neuromuscular centre in Newcastle. They focused specifically on boys who had no known family history of DMD. Their data show significant delays from parents’ first concern to final diagnosis with the mean age of onset of symptoms being 32 months (range 8–72 months), mean age of first engagement with a health professional 42.9 months, mean age at which the creatine kinase (CK) was checked 50 months (range 14–91 months) and mean age at which diagnosis was confirmed 51.7 months. One of the main reasons for diagnostic delay was that CK was only performed once the child had seen a consultant paediatrician which could take many months; for one individual, this resulted in an exceptional delay of 86 months.

van Reiten et al propose that screening for DMD should be part of the routine 2-year child health surveillance programme and that perhaps CK testing could be performed by primary care. They have suggested a screening mnemonic MUSCLE: M=motor milestone delay, U=unusual gait, S=for speech delay, C=CK ASAP, L=leads to, E=Early diagnosis.

Early diagnosis is even more important now than ever before, and missing the window of opportunity for corticosteroid treatment may have a serious adverse effect on long term outcome. Furthermore, new disease modifying treatments are currently undergoing clinical trials and may be licensed for treating boys with DMD in the near future. These disease modifying treatments are likely to be most effective when administered at an earlier age. There has never been a more important time for early diagnosis for DMD and we can now inform parents of newly diagnosed boys that they should expect their son to live well into adulthood and, for those without significant learning difficulty, they should prepare him for further education, employment and even independent living.

References

Footnotes

  • Competing interests None.

  • Provenance and peer review Commissioned; internally peer reviewed.

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