SMA vs α-SMA — spinal muscular atrophy or smooth muscle actin?
In this platform, SMA means 5q spinal muscular atrophy: the SMN1-linked motor neuron disease. By contrast, α-SMA means alpha smooth muscle actin, encoded by ACTA2, a contractile protein found in smooth muscle and widely used as a myofibroblast marker. The disease and the molecule are biologically distinct despite their overlapping labels.
Why literature searches collide
The bare token SMA is ambiguous in titles, abstracts, keywords, and automated indexing. A query that relies on that token alone can mix motor neuron disease research with fibrosis, vascular biology, wound healing, and other work that measures ACTA2 expression. Disease-anchored terms avoid most of this collision before exclusions are needed.
In our own corpus scan (2026-08-02), all abbreviation collisions together accounted for 16.4 % of the 17,670 sources retrieved by the bare token SMA. α-SMA/ACTA2 was the largest single block within that share. This is a dated measurement of our corpus and query procedure, not a general estimate for the biomedical literature.
Two PubMed traps
- "spinal muscular atrophy"[MeSH] is not a valid MeSH heading and returns 0 records. The heading is Muscular Atrophy, Spinal (D009134).
- A NOT (ACTA2 OR "smooth muscle actin") filter removes practically nothing from a set already anchored to SMN1 or SMN2. The contamination arises from the unqualified token SMA, not from anchored disease queries.