Male patients with spinal muscular atrophy (SMA) may experience a greater degree of symptom severity than female patients, according to a study recently published in the Journal of Neurology, Neurosurgery & Psychiatry.

“Gender should be considered as a factor predictive of disease severity and progression in SMA patients,” the authors wrote.

After a retrospective analysis of the data, the researchers observed that the proportion of patients who could not walk was significantly increased among male individuals, with a ratio of sitters/walkers of 46/38 vs 19/38 for female patients.

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Likewise, motor function impairment seemed to occur more predominantly in male patients. The median Hammersmith Functional Rating Scale Expanded score was 16 points for male patients on average, while female patients scored more than double, with 40 points. The upper limb segment of the test did not showcase a statistically significant difference between the sexes.

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Genotype may also play a role in disease severity. The study reported that in participants with SMA type 3 who carried 3 or 4 copies of the SMN2 gene, female sex was correlated with a longer ambulation time.

This cross-sectional study included 165 patients previously diagnosed with SMA, 61.2% of whom were male and 38.8% of whom were female. The median age of onset varied from 0 to 28 years of age, with a median of 3 years. Female patients exhibited a slightly earlier onset than male patients at 3 vs 4 years on average, respectively.

The most common subtype was SMA type 3, present in 85.5% of the cases, followed by SMA type 2 in 12.7% of patients and SMA type 4 in just 1.8% of patients.

“Previous studies suggested some discrepancies of the gender-related adult SMA natural history in terms of age at presentation and age of [loss of ambulation], but our study reveals the magnitude of the gender effect on motor function tested with objective outcome measures,” the study authors concluded.


Maggi L, Bello L, Bonanno S, et al. Adults with spinal muscular atrophy: a large-scale natural history study shows gender effect on disease. J Neurol Neurosurg Psychiatry. Published online October 11, 2022. doi:10.1136/jnnp-2022-329320