Hereditary pyropoikilocytosis was originally described by Zarkowsky et al. (1975) as a distinct hemolytic anemia characterized by microspherocytosis, poikilocytosis, and an unusual thermal sensitivity of red cells. HPP is a subset of hereditary elliptocytosis (see 611804) due to homozygous or compound heterozygous mutations in spectrin leading to severe disruption of spectrin self-association (review by An and Mohandas, 2008).