SMA classically includes four types (I to IV) depending on the age of onset of the deficit and the maximum motor ability achieved by the patient. Type III represents one of the smallest contingents of patients (15-20% of the total, depending on the study) and has been the subject of less observational studies than the more frequent types I and II.
In an article published in August 2021, English teams from Newcastle and London report work aimed at obtaining more follow-up data in a population of children with type III SMA who have lost walking. Force measurements, respiratory function studies and function scores were used to trace the natural history, over a two-year period, of 24 treatment-naive patients. For 16 of them, the researchers had scores from the Revised Upper Limb Module (RULM), a tool for assessing upper limb function. The evolutionary slopes observed confirm the existence of a non-negligible functional degradation over time, RULM and vital respiratory capacity often being correlated. This study takes place in the particular context of the United Kingdom where patients with type III SMA had, at the time (2019), very difficult access to innovative therapies.
