Early recognition of Duchenne muscular dystrophy: where could we improve?

Background: Duchenne muscular dystrophy (DMD) is caused by a mutation in the dystrophin gene and is the most common form of childhood-onset muscular dystrophy affecting approximately 1 in 3500 newborn boys. The disease is invariably progressive and most patients with DMD exhibit signs of muscle weakness before 5 years of age. Loss of ability to walk usually occurs between 10 to 13 years. Despite all the advances in management and treatment of DMD over the last decades, the mean age at diagnosis of DMD has been reported to be around the age of 4.5-5 years in several countries with a delay of about 2 years between the first symptoms are noted, and the diagnosis.

Objective: This retrospective study had objective to investigate the age at diagnosis of disease in a group of Brazilian patients followed in a tertiary center. We compared this age with the age that the symptoms started and age that therapy with steroids initiated. We compared our results with results from other countries that helped us to understand how we can improve pathway to reach an early diagnosis in our country, highlighting its strengths and weakness.

Methods: Data from one hundred and twenty-two (122) boys with Duchenne muscular dystrophy (DMD) that have been followed at Outpatient Child Neurology Service for neuromuscular disorders at the Hospital das Clínicas de São Paulo for 8 years (2014-2022).

Results: The mean age at onset of the disease was 3,3 years (ranged from 1 to 7 years). The mean age at diagnosis was 6,9 years (range 2-16 years). Steroid therapy was initiated in 120/122 patients (prednisolone in 36/120 and deflazacort 84/120). The mean age at started treatment with steroid was 7.3 years. The mean age of lost the capacity to walk was 10 years. Intragenic deletions, accounting for 58% (71/122) of all mutations was the most common mutational event. Duplications accounted for 14% and 20% had a point mutation (including 12/122 with nonsense mutation). In 7 boys (5%) was found an intronic mutation and in 2 the muscle biopsy confirmed the disease.

Conclusions: In this group of Brazilian patients with DMD, an important delay in diagnosis was observed which led to a delay in the beginning of steroid therapy. This late onset of therapy is probably related to an earlier age of loss of capacity to walk observed. Despite the availability of access to molecular testing we still observed difficult in recognizing the disease, which may be improved with wider dosage of serum CK in patients with motor/global development delay and weakness.

No conflict of interest has been declared by the author(s).

Publication History

Article published online:
18 September 2023