Thoracic circumference: A new outcome measure in spinal muscular atrophy type 1?

Since respiratory insufficiency is the first cause of morbidity and mortality in spinal muscular atrophy type 1 (SMA 1), specific respiratory outcome measures are needed to evaluate changes and assess innovative therapies. In this study, thoracic circumference (TC) was used as a proxy for chest growth and an indirect measurement of respiratory function. The anthropometric parameters including TC and head circumference (HC) were evaluated from birth to 13 months in 19 infants with SMA 1 and 124 control infants. TC was significantly decreased in the SMA 1 group from the first weeks of life. The control group TC/HC ratio =1 ( 0.04), and was not found to be associated with age. By contrast, it decreased with time in all infants with SMA 1 and those with a TC/HC ratio <0.85 died within 3 months. TC is a simple measurement that provided an index of chest growth and was used as evidence of early, progressive respiratory failure and under-development of the rib-cage in SMA 1. The TC/HC ratio decreased in all patients over time, reflecting the progression of the disease suggesting that TC/HC ratio could be a new measure for SMA 1 for measuring disease severity and prognosis. (C) 2019 Elsevier B.Y. All rights reserved.