The Effect of Ferritin Level on Respiratory Functions in Patients with β-Thalassemia Major

Introduction-Purpose

β-thalassemia major (β-TM) is an autosomal recessive disorder caused by mutations in the β-globin gene of hemoglobin. The disease is characterized by splenomegaly due to ineffective erythropoiesis, iron accumulation signs in tissues as a result of increased iron absorption, bone expansion due to increased erythropoietic activity, and decreased tissue oxygenation. One of the effected organ can be the lungs due to excessive iron deposition in these patients. The current study aimed to investigate the effect of serum ferritin level, which is known as a marker of iron accumulation in tissues, on pulmonary function tests (PFT) in patients with β-TM.

Methods and Materials

Patients aged ≥6 years who were regularly followed in the pediatric hematology section of Mersin City Research and Training Hospital with a diagnosis of β-TM were included. All patients received regular blood transfusion and iron chelation therapy. Study participants underwent PFT prior to blood transfusion in the pediatric pulmonology section

Results

A total of 43 patients with β-TM were studied. Included patients were divided into two groups according to the mean annual ferritin level; low ferritin group if below 2000 ml/ng and high ferritin group if above 2000 ml/ng. The low ferritin group was consisted of 19 patients and the high ferritin group was consisted of 24 patients. The characteristics of these two groups are shown in Table 1. There were no statistical significance in age, gender, body mass index, age at diagnosis, mean annual hemoglobin, splenectomy, cardiac involvement and oxygen saturation among both groups, but the number of annual transfusion was significantly higher in the high ferritin group than lower ferritin group.

When PFT parameters of both groups were compared, FVC (forced vital capacity) was statistically lower in the high ferritin group compared to the low ferritin group. Other parameters included FEV ₁ (forced expiratory volume in 1 second), FEV ₁/FVC ratio, PEF (peak expiratory flow) and FEF _25-75 (forced expiratory flow between 25% and 75% of vital capacity) were similar among groups. (Table 2)

Discussion

Patients with β-TM may accumulate iron in the interstitial area of the lungs which can lead fibrosis and impaired lung function over time. There are several studies investigated lung dysfunction and its etiology in these patients. Although the results of the studies are varied, the majority of them reported a restrictive pattern of respiratory dysfunction in thalassemia patients. Additionally, some studies showed the presence of mild or moderate obstruction in small airways and decrease in diffusion capacity with the increase of alveolar-capillary membrane thickness at advanced ages.

In the present study, we found that patients with β-TM who had high ferritin level showed restrictive type lung function compared to those with low ferritin level. There were no difference among the groups in obstructive parameters (i.e. FEV ₁, FEV ₁/FVC, FEF _25-75) of PFT. In the literature, studies investigating PFT in patients with high ferritin levels had variable results, impaired or no change, in pulmonary status.

In conclusion, loss of respiratory function and impaired tissue oxygenation in patients with β-TM may develop over time due to iron deposition in the interstitial area. PFT assessment of these patients is essential and recommended for the detection of early lung disease. Routine PFT follow in patients with β-TM of high ferritin values is highly important.