Misidentification of unstable, low oxygen affinity hemoglobin variant.

Background: We present a case of Hemoglobin (Hgb) Louisville in a 6-y old girl presenting with hypoxia and mild hemolytic anemia.

Methods: Hgb Louisville is a rare, unstable hemoglobin variant with low oxygen affinity, but initial workup of this case using widely-available hemoglobin fractionation methods was unable to differentiate this variant from normal hemoglobins.

Results: This resulted in a delayed diagnosis.