The suspicion of IO is usually raised by the finding of elevated ferritin levels, defined as >300 mg/L in males and >200 mg/L in females [38]. However, hyperferritinemia may potentially be found in 5.9–19.0 % of healthy individuals [24]. Moreover, since ferritin is an acute-phase reactant protein and is released in the presence of inflammation and from necrotic or lysed cells, it is common to observe its elevation in individuals who do not have IO [3]. Therefore, it is essential to associate ferritin results with transferrin saturation (TS). A TS >45 % in men and women has been defined as elevated [3] indicating that individuals should be investigated for IO. Family members of patients diagnosed with HC and patients with increased liver iron, evident by liver biopsy or by MRI, should undergo biochemical and genetic testing [3,4].

Patients with high ferritin levels but with TS <45 % very probably do not have IO and, as already mentioned, other factors should be investigated to determine the cause of hyperferritinemia. Patients with high ferritin levels and with TS <45 % without a clear cause, should be observed at least annually with measurements of serum ferritin and TS.

An elevated serum ferritin in association with low TS may occur in three pathological states that might result in iron tissue deposition: metabolic hyperferritinemia, ferroportin disease and aceruloplasminemia [39]. Metabolic hyperferritinemia should be suspected when there is an insulin resistance syndrome with mild hepatic iron excess. Ferroportin disease (A-form) is characterized by predominant macrophage iron excess and absent or mild iron-related complications. Hereditary aceruloplasminemia is associated with major hepatocyte IO and diabetes mellitus, with the common finding of anemia and the presence of a neurological syndrome [39]. Once there is a suspicion of one of these conditions, targeted clinical and/or genetic investigation is mandatory, in conjunction with the investigation of tissue iron deposition by T2* MRI [3].

Ferritin levels are often increased in chronic inflammatory conditions, liver disease, high alcohol consumption, obesity fatty liver, insulin resistance, poorly controlled diabetes mellitus, and metabolic dysfunction [13,40]. Unlike patients with HC, patients with metabolic hyperferritinemia have preserved production of hepcidin, and total iron body stores range from normal to a moderate level of IO [13]. Although iron levels in metabolic hyperferritinemia are not as high as those seen in HC, excess iron leads to the formation of reactive oxygen species and subclinical inflammation, worsening glucose and lipid metabolism, fibrogenesis and carcinogenesis [13].

In addition to the metabolic causes described above, active liver disease should also be evaluated in patients with evidence of IO. Alcoholic liver disease and hepatitis C infection may lead to IO and reticuloendothelial iron deposition [39]. Of note, iron removal by phlebotomy has been reported to improve the rate of response to interferon treatment in hepatitis C patients [41], although with the use of direct-acting antivirals, IO seems not to be a barrier to achieve response [42].

Finally, in patients diagnosed with IO, hematological diseases that lead to ineffective erythropoiesis and increased iron absorption (i.e., hemolytic anemias, myelodysplastic neoplasms) should be regularly investigated, even if they are not regularly transfused.

The classic HFE mutations, C282Y and H63D, should, of course, be investigated in patients suspected of IO, since HFE C282Y homozygosity can result in a potentially severe phenotype of HC, and the heterozygous phenotypes of C282Y/–, H63D/– and C282Y/H63D may also result in IO when combined with other genetic and environmental risk factors [2–4,14]. It is important to emphasize that the association of C282Y/H63D should not be classified as classic HFE hemochromatosis since this genotype has minimal or no clinical penetrance. In patients with this association (C282Y/H63D), mutations and deletions in HFE and non-HFE genes should be investigated. Furthermore, causes of liver disease should be investigated. Moreover, since the incidence of HFE mutations in Brazilian patients with HC is much lower than that observed in Northern European populations, investigation of other mutations in genes involved in iron metabolism should be considered for patients that do not harbor HFE mutations or who are not C282Y homozygotes. Taking into account previous Brazilian studies that evaluated non-HFE mutations in IO patients [28–30], the investigation of mutations of the TFR2, SCL40A1, HJV, HAMP, BMP6 and SLC11A1 genes might be valuable. However, it is very important to emphasize that, in the few available studies in Brazil, the number of identified patients with non-HFE mutations is quite low and in many patients with IO, no mutations were found. This strongly indicates that further studies in larger multicentric cohorts should be carried out to fully clarify the mutation spectrum of IO in Brazil. If available, a broader study with next-generation sequencing, by whole exome or complete genome sequencing, should be carried out.

If a diagnosis of early-onset HC is suspected (within the second or third decades of life, family history, hypogonadotropic hypogonadism or unexplained heart failure), sequencing of the HAMP and HJV genes is recommended [39]. If there is clinical suspicion of hereditary aceruloplasminemia, ceruloplasmin levels should be evaluated [39].

As already mentioned, in some cases, the genes for porphyria cutanea tarda and the β-globin gene (or HBB gene) should be sequenced when clinically suspected.

If not adequately treated in an early phase, excess free iron may lead to progressive tissue damage, with subsequent cardiac failure, cirrhosis and endocrine disfunction [1]. Additionally, as already described, high serum levels of ferritin have been associated with the amount of hepatic lipid accumulation, the severity of insulin resistance and features of metabolic dysfunction [13]. For this reason, decisions require individualized clinical assessment and patients with evidence of IO should be treated appropriately even if a specific genetic mutation cannot be identified. Ideally, patients with suspected IO (high ferritin and high TS) should be evaluated for liver iron concentration at diagnosis using T2* MRI in order to estimate the amount of iron deposition and to guide treatment [2]. Patients diagnosed with early-onset forms of HC should also be evaluated for cardiac iron deposition by cardiac T2* MRI [3].

Patients with no (or minimal) symptoms, but with persistently increased levels of serum ferritin, TS higher than 45 % and increased liver iron estimated by MRI, should be treated by phlebotomy in order to prevent organ damage. The management of patients is determined by their phenotypic presentation and the presence of associated cofactors, not by the genotype alone [2,3,13]. Treatment of risk factors and comorbidities is mandatory [2]. Alcohol intake should be restricted [3]. The initiation and maintenance of a schedule of phlebotomies is determined by serum iron studies (ferritin and TS), and the MRI, if available [2].

During the initial phase, the performance of phlebotomies in the range of 400–500 mL, according to body weight, weekly or every two weeks has been proposed [38]. The main treatment goal is to lower ferritin levels, with a serum ferritin target of 50 µg/L, although, in real-life, levels up to 100 µg/L are acceptable, even in the induction phase. During the maintenance phase, one phlebotomy is performed every 1–4 months, depending on the patient’s iron status [38], with the target serum ferritin being around 50–100 µg/L3. Although the reduction of TS to <50 % should be considered as highly desirable, in some patients this reduction is slow and difficult to achieve. Thus, the real target to guide treatment must be ferritin levels and not TS. The clinical implications of the maintenance of high TS for long periods with concomitantly low ferritin levels are not yet well understood [43,44]. If hemoglobin concentrations are <12 g/dL, the volume or frequency of phlebotomy should be decreased; if hemoglobin falls below 11 g/dL, phlebotomy should be discontinued until the causes of anemia can be assessed and adequately treated [3].

The role of iron depletion by phlebotomy in metabolically induced high ferritin levels remains an open question. In these patients, the maintenance of ferritin levels <50 µg/L does not seem to ameliorate metabolic endpoints (i.e., glucose control), nor transaminase levels or the liver fibrosis score [38]. However, if there is evidence of moderate or severe iron accumulation (defined by ferritin >1,000 ng/mL, or metabolic hyperferritinemia with a MRI estimative of >74 µmol/g of iron in the liver), phlebotomy should be considered, together with close monitoring of hemoglobin levels and adverse events [13] (using a cautious protocol of phlebotomy).

Since iron-chelating agents are not superior to therapeutic phlebotomy and usually cause adverse events, they are not routinely recommended for the treatment of IO in patients who are not anemic and who do not have other difficult issues regarding phlebotomy (inaccessible veins, needle phobia) [2,3]. However, iron-chelating agents can be used in association with phlebotomies in patients with severe IO, such as in cases of early-onset HC and cardiac iron deposition [3,38]. Proton pump inhibitors can also be an adjuvant to phlebotomy for some patients, since they reduce intestinal iron absorption [3]. Apparently, dietary heme or nonheme iron restrictions have no significant relationships with iron body content, and there is no strong evidence that dietary restrictions have an important role in IO treatment [46]. However, if the patient accepts the suggestion, black tea with meals and a vegetarian diet may be prescribed since these seem to be beneficial for some patients [47,48]. Erythrocytapheresis is very effective and can be considered where available to treat HC patients, however it is more expensive and less available than phlebotomy [38].

When guidelines are proposed, they must consider the best available evidence to help clinicians in taking the most appropriate decisions in specific clinical contexts. In the scenario of IO, advanced tools are certainly helpful for the diagnosis and management of this condition, particularly the complete genetic identification of mutations and quantification of tissue iron deposition by T2* MRI.

A frequent problem that many physicians may encounter in a country like Brazil, with limited resources and unequal access to technology in public health services is the impossibility to obtain an MRI estimate of liver iron or access to molecular diagnosis. Given the harmful consequences of untreated IO, as strongly suggested by published reports [43,44], it is recommended that patients with a very probable IO (elevated serum ferritin levels (>400 µg/L in men and >300 µg/L in women) for at least six months and TS higher than 45 %) should be treated with therapeutic phlebotomy targeting a serum ferritin of 50–100 µg/L, even if genetic investigation or MRI cannot be performed. We recognize that the numbers indicated here are somewhat arbitrary, but they are based on available evidence in the literature and also on the personal experience of several experts in the field.

The patients classified with "very probable IO" should be divided into two groups, the first with levels of ferritin higher than 1,000 µg/L and the second with ferritin between 400 µg/L and 1,000 µg/L. For those with ferritin higher than 1,000 µg/L and of course, high TS, there are a number of indications that liver damage secondary to IO may be very probable, and phlebotomy should be carried out following the traditional protocol, as described earlier. On the other hand, for patients who have ferritin levels of between 400 µg/L and 1,000 µg/L and elevated TS, the evidence supporting phlebotomies is weaker and these individuals should undergo careful individual analysis regarding their clinical status. However, a recent relevant study showed that patients with classic C282Y/C282Y HFE-related hemochromatosis with ferritin levels of between 300 µg/L and 1,000 µg/L demonstrated a significant clinical improvement when submitted to repeat phlebotomies. Thus, for individuals with intermediately elevated ferritin levels (between 400 µg/L and 1,000 µg/L), a specialized and carefully designed treatment protocol is proposed. Phlebotomies should be undertaken every three or four weeks. Hemoglobin levels must be monitored before each procedure and ferritin measured every 30 days. The treatment target should be ferritin of 100 µg/L. If Hb is ≤12 g/dL, the procedure should be stopped. After three or four phlebotomies the patient should be carefully reevaluated. After the target of 100 µg/L is reached, patients should be kept in the usual maintenance phase, with 2–4 phlebotomies per year, and checked for ferritin and TS every six months.