Hexokinase deficiency is an autosomal recessive genetic disease characterized by nonspherocytic hemolytic anemia. Jaundice, splenomegaly, pallor and constitutional symptoms such as lethargy and fatigue are main symptoms. A full laboratory workup, including genetic studies, are required to exclude more common causes of hemolytic anemia and confirm hexokinase deficiency as the underlying cause.
Hexokinase deficiency (HKD) is a very rare occurrence in clinical practice, as only 17 families suffering from this condition have been described in literature by the beginning of the 20th century . The only clinical sign of HKD is the appearance nonspherocytic hemolytic anemia   , which can be accompanied by jaundice, lethargy, pallor, and fatigue. Severe neonatal jaundice may be seen as well, while splenomegaly and central nervous system symptoms such as mental retardation are also described in hemolytic anemias that arise due to glycolytic enzyme deficiencies . The main reason for the red-blood-cell (RBC) related pathology lies in the fact that hexokinase 1 (HK1), expressed predominantly in erythrocytes, is affected by genetic mutations that render RBCs unable to produce energy from the glycolytic pathway, as HK is a pivotal enzyme for this process   . Earlier studies have associated latent diabetes and panmyelopathy with this condition , but because of a very low number of cases, these claims remain to be solidified. The clinical presentation of hexokinase deficiency is similar to the presentation of the pyruvate kinase deficiency; however, the anemia is more severe.
The diagnosis of HK should be considered when all other causes of hemolytic anemia have been excluded. Firstly, a complete blood count (CBC) should be obtained, including levels of hemoglobin, mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC), red cell distribution width (RDW), as well as reticulocyte and platelet count . If anemia without an identifiable cause is noted, a peripheral blood smear should be done, and hemolysis of RBCs, but in the absence of spherocytosis, is a diagnostic hallmark of HK deficiency. Furthermore, the direct coombs test; used to exclude autoimmune causes of hemolytic anemia like warm antibody hemolytic anemia (associated with the use of drugs, systemic lupus erythematosus or chronic lymphocytic leukemia), cold agglutinin disease and paroxysmal cold hemoglobinuria, should be performed as well . In addition, bilirubin and lactate dehydrogenase (LDH) will be markedly elevated in hemolytic anemias, whereas reduced haptoglobin and detection of hemoglobin and hemosiderin in urine is frequently observed . If enzymopathy remain the only diagnostic possibility for anemia, genetic tests to determine which enzyme is deficient and responsible for the symptoms must be conducted, especially in the presence of a positive family history, but very few laboratories possess the tools for such advanced diagnostic procedures . Nevertheless, if valid clinical and laboratory criteria exist, genetic studies must be performed.