The authors of a recent article in CHEST (September 2004)1 described their management outcomes for patients with infantile spinal muscle atrophy (SMA) without comparing them to other studies. First, the system they used for classifying SMA, that is, by age of onset, has been largely abandoned because of its inherent inconsistencies in favor of stratification by disease severity. A more widely accepted classification is as follows: type 1, children who can never sit; type 2, children who can sit but not stand; and type 3, children who can walk. The authors’ type 3 is “for onset after the age of walking”; however, it is not uncommon for these children to be symptomatic in infancy but then never sit or walk, sit, or even begin walking at age 3 years. Indeed, while SMA is a continuum of pathology, “age at onset” is more a reflection on the astuteness of the observer than of disease severity. Their “intermediate type 1” patients who can “raise their heads,” many of whom, no doubt, can sit, would be classified as being type 2 by the majority of clinicians today. This is important because their “type 1 intermediates,” shown in Figure 1 of their article, have vital capacities (VCs) as high as 75% of normal. In our 112 children with type 1 SMA, who could never sit, and who developed respiratory failure and the need for gastrostomy tubes before their second birthdays, the average maximum VC ever attained was 142 mL. The VC did not increase with age, and the high value at any time (to age 11 years) for any patient was 300 mL, or about 10% of normal values. Thus, the typical children with type 1 SMA who we described correspond to the “true type 1s,” patients who the authors reported invariably had died or had undergone tracheotomy.