  We describe how thermally produced anti-electron neutrinos ($\bar\nu_e$) from
the homologously collapsing core of a supermassive star ($M \ga 5\times10^4
M_\odot$) can lead to significant deuterium enrichment in the ejected envelope
of such a star. Deuterium-enriched material at high redshift might then serve
as a clue to the existence of pregalactic supermassive stars. Conceivably, the
ejected deuterium-enriched material could intercept the line of sight to a
distant QSO and mimic a Lyman limit absorber. In such a case, the deuterium
abundance inferred from absorption lines might not reflect the true primordial
abundance of deuterium. We discuss relevant theoretical uncertainties in
supermassive star physics as well as potential observational signatures in
Lyman $\alpha$ absorber clouds for processing by stars of this kind.
