Clinical Description
To date, approximately 120 individuals have been identified with juvenile hemochromatosis [De Gobbi et al 2002, Merryweather-Clarke et al 2003, Roetto et al 2003, Delatycki et al 2004, Jacolot et al 2004, Matthes et al 2004, Roetto et al 2004, Island et al 2009, Lok et al 2009, Hattori et al 2012, Kong et al 2019]. The following description of the phenotypic features associated with this condition is based on these reports.
Table 2.
Features of Juvenile Hemochromatosis
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Feature | HJV Hemochromatosis: % of Persons w/Feature | HAMP Hemochromatosis: Proportion of Persons w/Feature 1 |
---|
Cardiomyopathy | 35%-37% | 4/7 |
Hypogonadotropic hypogonadism | 67%-91% | See footnote 2. |
Reduced glucose intolerance / diabetes | 30%-57% | 7/8 |
Liver fibrosis | 44%-58% 3 | 6/7 4 |
Liver cirrhosis | 27%-42% |
Hyperpigmentation | 24.5% | See footnote 2. |
- 1.
In HAMP hemochromatosis data are limited and clinical descriptions have been incomplete although similar to HJV hemochromatosis.
- 2.
Not enough information is available to determine the proportion of individuals with this feature.
- 3.
Not all individuals in reported studies underwent liver biopsy.
- 4.
Proportion of persons with HAMP hemochromatosis with either liver fibrosis or cirrhosis
Juvenile hemochromatosis is characterized by early-onset severe iron overload. Individuals with juvenile hemochromatosis typically present in the first to third decade of life; however, adult presentation has been described in individuals with HJV hemochromatosis [Koyama et al 2005, Ravasi et al 2018, Kong et al 2019], expanding the spectrum of disease phenotypes related to HJV pathogenic variants from classic juvenile hemochromatosis at one extreme to a late-onset adult form at the other extreme. Males and females are equally affected.
Individuals with juvenile hemochromatosis are rarely diagnosed before significant iron overload occurs. Prominent clinical features include hypogonadotropic hypogonadism, cardiomyopathy, diabetes and glucose intolerance, arthropathy, and liver fibrosis or cirrhosis.
Cardiac. The prevalence of cardiac disease is strikingly high [De Gobbi et al 2002, Kong et al 2019] and in some individuals is the presenting finding [Filali et al 2004]. Myocardial iron accumulation induces the development of restrictive cardiomyopathy with early diastolic dysfunction that may progress towards dilated cardiomyopathy. Heart failure is the main cause of death in untreated individuals with juvenile hemochromatosis [Murphy & Oudit 2010]. A variety of arrhythmias and sudden death can also occur in individuals with severe iron overload although further investigations to clarify the etiology and clinical relevance of iron overload-induced arrhythmias are needed [Shizukuda & Rosing 2019]. Iron removal can significantly improve and/or normalize cardiac function [Murphy & Oudit 2010].
Hypogonadotropic hypogonadism characterized by low levels of gonadotropins (FSH and LH) and testosterone is the most frequent endocrinologic complication in individuals with iron overload due to juvenile hemochromatosis [De Gobbi et al 2002, Borgna-Pignatti et al 2004]. It causes decreased libido and infertility, amenorrhea in females, and impotence in males, and contributes to the development of osteoporosis. Iron removal in early stages can lead to symptomatic improvement or resolution and normalization of hormonal indices [Angelopoulos et al 2006, Pelusi et al 2016].
Diabetes mellitus. Most of the information on diabetes development has been obtained in individuals with HFE hemochromatosis, where the pathogenesis of glucose intolerance and diabetes is likely multifactorial. Autopsy findings in individuals with hemochromatosis showed variable iron deposition in the exocrine pancreas and in beta cells together with loss of endocrine granules. It can be hypothesized that a severe and rapid iron overload in the exocrine pancreas could induce an initial beta-cell oxidative stress followed by iron accumulation and decreased insulin secretory capacity secondary to beta-cell apoptosis and desensitization of glucose-induced insulin secretion [Backe et al 2016]. Glucose intolerance or diabetes may require oral agents or insulin administration. Phlebotomy has a variable impact on diabetes control. In general, it may prevent progression if started in the earlier stages of disease, although the majority of individuals with diabetes will experience no significant change or worsening in their glucose metabolism control [Angelopoulos et al 2007, Pelusi et al 2016].
Liver. Although hepatomegaly is usually included among the earlier manifestations of juvenile hemochromatosis there is no information on its frequency as it is often poorly noted in clinical evaluations. Because the liver can compensate for iron toxicity, cirrhosis takes decades to develop. While in individuals with HFE hemochromatosis a serum ferritin value above 1000 ng/mL is a validated marker of increased risk of severe hepatic fibrosis/cirrhosis [Allen et al 2010], there are no data available for juvenile hemochromatosis. Therefore, assessment by liver fibroelastography and/or liver biopsy is mandatory. Environmental (e.g., alcohol consumption, steatosis, coexistent viral infection) and possibly genetic factors can modify the risk for cirrhosis [Brissot et al 2018]. Based on data related to other liver disease and HFE hemochromatosis [Falize et al 2006] it can be assumed that iron depletion can improve fibrosis unless cirrhosis is fully established. Hepatocellular carcinoma is rarely reported in individuals with juvenile hemochromatosis [Ramzan et al 2017]. A possible explanation is that untreated individuals with juvenile hemochromatosis die prematurely as a result of cardiac complications.
Skeletal. Articular symptoms, arthralgias, and/or arthritis was reported in seven of eight individuals with HJV hemochromatosis [Vaiopoulos et al 2003]. The age at onset of arthropathy ranged from 20 to 45 years. In two individuals arthropathy preceded other symptoms of juvenile hemochromatosis. The involved joints were most frequently metacarpophalangeal joints; knees, lumbar spine, and shoulder and metatarsophalangeal joints were variably involved. Four of the six individuals evaluated had osteopenia or osteoporosis, common complications in individuals with prolonged hypogonadism. However, a more recent study of 73 individuals with HJV hemochromatosis reported a very low frequency of osteopathy (7%) [Kong et al 2019] – a finding to be taken with caution because osteopenia and osteoporosis can be underestimated if not sought with appropriate investigations through bone densitometry (DXA, dual-energy x-ray absorptiometry). Iron removal, in contrast with the visceral manifestations, often did not mitigate orthopedic complications [Sahinbegovic et al 2010].
Skin. A recent review reported hyperpigmentation in approximately 25% of individuals with HJV hemochromatosis [Kong et al 2019] – a finding that contrasts with older reports of skin hyperpigmentation at diagnosis in about 90% of individuals with hemochromatosis. Hyperpigmentation developed very gradually. This may suggest that iron-induced skin changes take too long to manifest in the majority of individuals with juvenile hemochromatosis.
If juvenile hemochromatosis is detected early and treated with phlebotomy to achieve iron depletion, morbidity and mortality are greatly reduced.
Other. Although individuals with juvenile hemochromatosis may develop adrenocortical insufficiency or hypothyroidism, these complications are rare [Varkonyi et al 2000, Pelusi et al 2016].
Heterozygotes and digenic inheritance. Heterozygous pathogenic variants in HAMP, HJV, and/or TFR2 have been shown to increase the risk for iron overload in HFE p.Cys282Tyr heterozygotes [Merryweather-Clarke et al 2003] and to increase iron burden in HFE p.Cys282Tyr homozygotes [Jacolot et al 2004, Majore et al 2004, Pietrangelo et al 2005]. However, only a very small proportion of individuals with HFE hemochromatosis are reported to have polygenic inheritance due to pathogenic variants in HAMP and HJV.