Morphology and kinetics of erythropoiesis in haemoglobin H disease

Abnormal red blood cell morphological changes in thalassaemia associated with iron overload and oxidative stress

AIMS

Iron overload is a major factor contributing to the overall pathology of thalassaemia, which is primarily mediated by ineffective erythropoiesis and shorter mature red blood cell (RBC) survival. Iron accumulation in RBCs generates reactive oxygen species (ROS) that cause cellular damage such as lipid peroxidation and RBC membrane deformation. Abnormal RBCs in patients with thalassaemia are commonly known as microcytic hypochromic anaemia with poikilocytosis. However, iron and ROS accumulation in RBCs as related to RBC morphological changes in patients with thalassaemia has not been reported.

METHODS

Twenty-one patients with thalassaemia, including HbH, HbH with Hb Constant Spring and β-thalassaemia/HbE (splenectomy and non-splenectomy) genotypes, and five normal subjects were recruited. RBC morphology was analysed by light and scanning electron microscopy. Systemic and RBC iron status and oxidative stress were examined.

RESULTS

Decreased normocytes were observed in the samples of patients with thalassaemia, with RBC morphological abnormality being related to the type of disease (α-thalassaemia or β-thalassaemia) and splenic status. Target cells and crenated cells were mainly found in splenectomised patients with β-thalassaemia/HbE, while target cells and teardrop cells were found in non-splenectomised patients. Patients with thalassaemia had high levels of serum ferritin, red cell ferritin and ROS in RBCs compared with normal subjects (p<0.05). Negative correlations between the amount of normocytes and serum ferritin (r_s=-0.518, p=0.011), red cell ferritin (r_s=-0.467, p=0.025) or ROS in RBCs (r_s=-0.672, p<0.001) were observed.

CONCLUSIONS

Iron overload and its consequent intracellular oxidative stress in RBCs were associated with reduce normocytes in patients with thalassaemia.

Ferrokinetic and erythrokinetic studies in alpha and beta thalassaemia

Ferrokinetic and erythrokinetic studies were performed in 25 non-splenectomized patients with alpha or beta thalassaemia. Nine of these had HbH disease and six had HbE/beta thalassaemia or homozygous beta thalassaemia. In HbH disease, a mild anaemia was associated with severe peripheral haemolysis, increased splenic sequestration and only a moderate degree of ineffective erythropoiesis. By contrast, in the beta thalassaemia syndromes, a more marked anaemia was associated with prominent ineffective erythropoiesis and mild peripheral haemolysis. These findings indicate that the pathogenesis of anaemia in alpha and beta thalassaemia is different, haemolysis dominating in HbH disease and ineffective erythropoiesis in HbE/beta thalassaemia and homozygous beta thalassaemia.

Treatment of the thalassemia syndrome with splenectomy

Splenectomy was performed on 152 patients with thalassemia (thal), including 90 cases with Hb H disease, 48 cases with homozygous beta-thal, and 14 cases with Hb E-beta-thal. The therapeutic effect in Hb H disease was 83.3%, and 32.3% in Hb E-beta-thal and beta-thal. In Hb H disease, the hemoglobin (Hb) level increased 30 g/l in 14 of 29 cases. After splenectomy, the life-span (T1/2) of 51Cr RBC in Hb H and Hb E-beta-thal increased to 18.2 +/- 2.6 and 18.2 days, respectively. The number of inclusion (Heinz) bodies attached to the RBC membrane increased after surgery. The interdermal delayed supersensitivity reaction became negative in seven of 26 cases of Hb H disease; the IgG also decreased after surgery. The number of PAS positive foam cells in the spleen correlated to Hb level after surgery. Infection is a common complication.