Abstract
Patients with myelodysplastic syndromes (MDS), osteomyelofibrosis (OMF), or severe aplastic anemia (SAA) suffer from ineffective erythropoiesis due to pancytopenia, which is treated with red blood cell transfusion leading to iron overload. Especially in low-risk patients with mean survival times of > 5 years, potentially toxic levels of liver iron concentration (LIC) can be reached. We hypothesize that the higher morbidity seen in transfused patients may be influenced by iron toxicity. Following a meeting in Nagasaki 2005, a consensus statement on iron overload in myelodysplastic syndromes has been published, however, there is still no common agreement about the initiation of chelation treatment in MDS patients. In the present study, a total of 67 transfused patients with MDS (n = 20, age: 17 – 75 y), OMF (n = 4, age: 48 – 68 y), SAA (n = 43, age: 5 – 64 y) were measured by SQUID biomagnetic liver susceptometry (BLS) and their liver and spleen volumes were scanned by ultrasound at the Hamburg biosusceptometer. Less than 50 % were treated with DFO. LIC (μg/g-liver wet weight, conversion factor of about 6 for μg/g-dry weight) and volume data were retrospectively analyzed in comparison to ferritin values. Additionally, 15 patients (age: 8 – 55 y) between 1 and 78 months after hematopoietic cell transplantation (HCT) were measured and analyzed. LIC values ranged from 149 to 8404 with a median value of 2705 μg/g-liver, while serum ferritin (SF) concentrations were between 500 and 10396 μg/l with a median ratio of SF/LIC = 0.9 [(μg/l)/(μg/g-liver)] (range: 0.4 to 5.2). The Spearman rank correlation between SF and LIC was found to be highly significant (RS = 0.80, p < 0.0001), however, prediction by the linear regression LIC = (0.83± 0.08)·SF was poor (R2 = 0.5) as found also in other iron overload diseases. Although iron toxicity is a long-term risk factor, progression of hepatic fibrosis has been observed for LIC > 16 mg/g dry weight or 2667 μg/g-liver (Angelucci et al. Blood2002; 100:17–21) within 60 months and significant cardiac iron levels have been observed for LIC > 350 μmol/g or 3258 μg/g-liver (Jensen et al. Blood2003; 101:4632-9). The Angelucci threshold of hepatic fibrosis progression was exceeded by 51 % of our patients, while 39 % were exceeding the Jensen threshold of potential risk of cardiac iron toxicity. The total body iron burden is even higher as more than 50 % of the patients had hepatomegaly (median liver enlargement factor 1.2 of normal). A liver iron concentration of about 3000 μg/g-liver or 18 mg/g-dry weight has to be seen as latest intervention threshold for chelation treatment as MDS patients are affected by more than one risk factor. A more secure intervention threshold would be a LIC of 1000 μg/g-liver or 4 – 6 mg/g-dry weight, corresponding with a ferritin level of 900 μg/l for transfused MDS patients. Such a LIC value is not exceeded by most subjects with heterozygous HFE-associated hemochromatosis and is well tolerated without treatment during life-time. Non-invasive liver iron quantification offers a more reliable information on the individual range of iron loading in MDS which is also important for a more rational indication for a chelation treatment in a given patient.
Aggregation pattern, sampling plan, and intervention threshold for Pezothrips kellyanus in citrus groves
