Hemoglobinopathies are considered a major public health problem in many countries, including Brazil, a fact explained by their frequency, genetic diversity and clinical importance. The unstable hemoglobin group is associated with congenital non-spherocytic hemolytic anemia due to instability of the hemoglobin molecule which can lead to the formation of characteristic inclusion bodies or Heinz bodies. Hb Köln beta 98(FG5) Val>Met is the result of the substitution of the amino acid valine for methionine at position 98 of the Beta chain of hemoglobin. Hemoglobin Köln reports are concentrated in Europe and in some parts of the Orient, such as northern Europe, among Jews, Czechoslovaks, Japanese, and also Koreans. A case was recently reported in India and, in Brazil, some cases have been known since 1993. This hemoglobinopathy is widely distributed, however, its frequency is extremely low when compared to the most frequent variants such as hemoglobin S (HbS) and C (HbC) in Brazil. Patients with Hb Köln usually present with mild hemolytic anemia characterized by reticulocytosis, splenomegaly and bilirubin, jaundice, and persistent dark urine excretion. In addition, some case reports describe Köln patients with priapism or persistent thrombocytopenia.

We report a case of Köln's Hemoglobin in a 54-year-old female patient with hemolytic anemia under investigation. Osmotic instability tests were performed with a NaCl solution, hemoglobin electrophoresis in cellulose acetate at alkaline pH in which the presence of a band migrating between A2 and S hemoglobins was observed, when the hemolysate was performed with 1% saponin, search for Heinz bodies with a 1:1 brilliant cresyl blue solution incubated at 37°C for 30 minutes, after which the bodies were identified in the blood smear. Upon suspicion of unstable hemoglobin, other standard laboratory procedures were performed, such as High Performance Liquid Chromatography (HPLC) with the Trinity®Premier Resolution Analytical Column equipment, in which a dosage of 3.18% HbA2 and 0.16% HbF was observed. The results corroborate the electrophoretic and chromatographic profile suggestive of heterozygosity for Hb Köln.

It is known today that there are 155 unstable hemoglobins identified worldwide and, of these, approximately 102 lead to hemolysis or abnormal oxygen affinity. In contrast the other variants do not show hematological abnormalities, but show instability in in vitro test. The phenotype of unstable variants of hemoglobin is diverse and dependent on the position of the mutation, which can lead to changes in the structure of the globin chain or of the hemoglobin molecule. Hb Köln is the most common of the unstable variants of hemoglobin and was first described by Pribilla in 1962. One of the main characteristics of unstable hemoglobins is the presence of Heinz bodies, which was curiously observed in this patient's red blood cells, corroborating data already described in the literature. Thus, a reliable detection of Hb Köln together with genetic counseling and prenatal diagnosis are essential to improve the well-being of patients.