US experts in Hawaii believe a sick whale spotted off the coast of Kauai may be suffering from scoliosis or curvature of the spine.
It is a rare disorder but scientists say they have seen it in other marine mammals such as dolphins.
The National Oceanic and Atmospheric Administration's marine mammal response coordinator, David Schofield, said officials were confident the whale was either born with the condition or acquired it over the course of its life.
The Honolulu Star-Advertiser newspaper reported that Schofield had ruled out a boat collision because it is not plausible that an animal hit by a boat would have retained the shape of such an injury.
A flight instructor on Kauai spotted the white, emaciated whale with a severely deformed spine, on Monday.
He said the 50 foot whale "appeared to be bent in half."