The intelligence quotient (IQ) of patients with Becker muscular dystrophy (BMD) and Duchenne muscular dystrophy (DMD) is lower than normal, a new study published in Neuropathology and Applied Neurobiology confirmed. The study also found a synergistic association between the number of affected isoforms and IQ in patients with DMD.

These findings underscore the importance of neuropsychological assessments following a diagnosis of BMD or DMD and periodically thereafter to determine progress so that necessary interventions can be implemented at home and school to ensure the optimal development of patients.

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To estimate IQ and the association between IQ and genotype in patients with BMD and DMD, a team of researchers led by Vicente Martínez-Vizcaíno, MD, PhD, from the Health and Social Research Center, Universidad de Castilla-La Mancha in Cuenca, Spain and Facultad de Ciencias de la Salud, Universidad Autónoma de Chile in Talca, Chile conducted a systematic review and meta-analysis of the literature.

The team analyzed 51 observational studies that determined the IQ and/or the IQ by genotype in patients with BMD or DMD.

These studies reported that the average IQ of BMD patients was 89.92, while that of DMD patients was 84.61. 

When they compared the IQ by genotype in patients with BMD, the researchers found that for Dp427−/Dp140+/Dp71+, the average IQ was 90.62, and for Dp427−/Dp140−/Dp71+, it was 80.73.

In patients with DMD, the average IQ associated with Dp427−/Dp140+/Dp71+ was 93.05, while for Dp427−/Dp140−/Dp71+, it was 81.78, and for Dp427−/Dp140−/Dp71−, it was 49.19. 

In patients with DMD, Dp427−/Dp140−/Dp71+ vs Dp427−/Dp140+/Dp71+ was associated with a 10.73-point reduction and Dp427−/Dp140−/Dp71− vs Dp427−/Dp140−/Dp71+ was associated with a 36.14-point reduction.

“There is a strong association between genotype and IQ in DMD,” the researchers concluded, “with the most affected patients being those with the Dp427−/Dp140−/Dp71+ and Dp427−/Dp140−/Dp71− genotypes.”


Pascual-Morena C, Cavero-Redondo I, Sequí-Domínguez I, Rodríguez-Gutiérrez E, Visier-Alfonso ME, Martínez-Vizcaíno V. Intelligence quotient-genotype association in dystrophinopathies: a systematic review and meta-analysis. Neuropathol Appl Neurobiol. Published online June 13, 2023. doi:10.1111/nan.12914