Primary haemochromatosis resulting in dilated cardiomyopathy arising out of mutation in HJV gene in Indian patients: a rare scenario

Abstract

Primary haemochromatosis (PH) is a genetic disorder of iron metabolism with multiorgan involvement due to mutations in HFE or more rarely haemojuvelin (HJV) gene. Cardiac involvement results in dilated cardiomyopathy with reduced ejection fraction and progressive heart failure. PH is rarely reported from India and cardiomyopathy due to PH from HJV mutations is thought to be uncommon. We report two families with cardiomyopathy resulting from PH. Diagnosis was suspected on the basis of skin pigmentation, markedly elevated serum ferritin and transferring saturation. Genetic testing revealed a rare mutation in HJV gene in one family. Being a treatable condition, PH should be suspected and investigated in cardiomyopathy patients in Indian subcontinent. If HFE is negative, analysis of non-HFE mutation should always be considered.

Background

Primary haemochromatosis (PH) is a genetic disorder characterised by excessive iron accumulation resulting in tissue injury in various body tissues. Its manifestations include infertility, diabetes, cirrhosis, bronze pigmentation of skin and cardiomyopathy. It is most commonly seen in Caucasian population from North Western Europe.¹ PH is thought to be rare in India and other Asian countries. There are only few case reports that have reported infertility and abnormal liver function test/cirrhosis as primary manifestation of PH in India.^2–7 PH leading to cardiomyopathy has been rarely reported from India.⁸

PH is a genetically heterogenous disorder caused by mutations in one or more different genes. It is commonly due to two mutations in HFE gene, C282Y and H63D, as reported in European patients. Whereas, the frequency of C282Y allele is close to 0 in Indian subcontinent.^{2 9} H63D mutation is found in India but it has not been found to cause iron overload in our population even in homozygotes.²

It is suggested that non-HFE gene mutations such as haemojuvelin (HJV) and hepcidin (HAMP) may be responsible for PH in Indian subcontinent.^{9 10} We report PH in two families of Indian origin, who presented with cardiomyopathy and one of them had a rare mutation in HJV gene.

Case presentation

Family 1: A 40-year-old woman, housewife, presented to emergency department with congestive heart failure (CHF). She was a known diabetic for past 5 years. 2D echocardiography revealed dilated cardiomyopathy (DCMP) with severe left ventricular (LV) systolic dysfunction (ejection fraction—20%). Haemochromatosis was suspected based on bronze pigmentation of skin and iron studies were ordered. Serum iron (400 mg/dL) and ferritin (2000 ng/mL) were markedly increased with transferrin saturation of 90%. She died within 2 days of admission due to cardiogenic shock.

Rests of the family members (a brother, father and mother) were screened. While elder brother had markedly elevated serum iron (273 mg/dL) and ferritin (1600 ng/mL) levels, these were normal in both the parents. He was also a known diabetic for past 3 years. 2D echocardiography, liver function test, serum follicle stimulating harmone (FSH) and testosterone levels were normal. MRI abdomen revealed (figure 1: axial T1-weighted and T2-weighted fast spin echo (FSE) sequences) revealed diffuse lowering of the liver (white asterisk) signal intensity with respect to spleen (black asterisk).

Figure 1.

(A, B) Axial T1-weighted and T2-weighted FSE sequences reveal diffuse lowering of the liver (white asterisk) signal intensity with respect to spleen (black asterisk). (C) Axial T1-weighted fat sat image reveals lowering of the pancreatic signal also (white arrow).

Genetic analysis was done by direct bidirectional Sanger sequencing. HFE, HFE2 and HAMP gene were screened for mutation analysis. The causative mutation was found to be homozygous mutation arising from nucleotide change c.1006G>T (p.Gly336Ter) occurring in exon 4 of HFE2 gene. This is a nonsense mutation leading to premature truncation of protein. This is consistent with patient’s phenotype.

Family 2: A 30-year-old man, a recent onset diabetic since past 5 months, presented with CHF. 2D echocardiography showed severe global hypokinesia with severe biventricular systolic dysfunction (LV ejection fraction- 20%)

Physical examination revealed bronze pigmentation of both hands (figure 2). Serum iron (139 mg/dL) and serum ferritin (4326 ng/mL) were increased with marked increase in transferrin saturation of 91.1%. Serum FSH (0.29 mIU/mL) and testosterone (0.05 ng/mL) were also found to be low.

Figure 2.

Bronze pigmentation of bilateral dorsae of hands.

MRI of upper abdomen revealed diffusely hypointense signal intensity of liver on all sequences with relative preservation of spleen and visualised bone marrow. These findings are specific of PH since preservation of spleen and bone marrow is not seen in secondary haemochromatosis.¹¹

Family members were screened with serum ferritin and transferrin saturation. Elder sister had significantly increased serum ferritin (960 ng/mL) and transferrin saturation of 98%. Rest of the family members (father, elder brother, younger brother and sister) had normal reports. Genetic analysis was negative for HFE gene mutation (282Y and 63D allele). Other mutations such as HJV and HAMP mutations could not be tested because of financial reasons.

Outcome and follow-up

Patient was started on iron chelation therapy with desferrioxamine mesilate and regular phlebotomies. Serum ferritin gradually decreased to 200 ng/mL. This lead to significant improvement in left ventricular ejection fraction from 20% to 45% and complete disappearance of heart failure signs and symptoms over 2 years.

Discussion

We report PH resulting in DCMP from Indian subcontinent, which is rare in this region. Only few case reports are available that report infertility and liver dysfunction as primary manifestations of PH in Indian patients.^2–7 Cardiac involvement due to PH has been rarely reported from India. It is thought that Indians have a different environmental or genetic background that protects them from cardiotoxicity.⁹ Both the families in the present case report had cardiac involvement with skin pigmentation and diabetes, which lead to suspicion of PH. Recently, cardiac involvement has also been reported from China in three patients.^{10 12} This suggests that Asians are not immune to cardiac involvement due to PH as thought previously. Only few cases of cardiomyopathy in this part of the world may be due to few reasons: first, PH itself is rare in Asia. Second, diagnosis of PH is not suspected hence not diagnosed. Also, skin pigmentation is difficult to recognise because of dark complexion of Indian patients. Manifestations of PH may be masked by iron deficiency, which is very common in developing countries.⁹

Common HFE alleles are rare in India. Common 282Y and 63D mutations are rare in people of Asian descent. Studies from Asia on occurrence of these mutations are scanty. Frequency of 282Y is close to 0.^{2 9} The 63D mutation has been found and the reported frequency is between 9.1% and 13.1% in various studies.^2–5 However, its role in causation of PH is not established. Subjects who are even homozygotes have no evidence of iron overload. Thus, primary iron overload in Indians is non-HFE type.

In a study of seven patients from Asia, all the cases occurred due to non-HFE mutations—HJV (five patients), hepcidin (one patient) and ferroportin (one patient).⁸ A recent study from China also found non-HFE mutations as the major culprits in this part of world.¹⁰ In this Chinese study, two cases of cardiac involvement were reported due to mutations in HFE2 gene and transferring receptor 2 gene. HFE2 gene in their study involved c.860 T>G nucleotide change, while in our study c.1006G>T (p.Gly336Ter) was involved. Recently in year 2018, Dhillon et al⁸ have reported the same variant among four north Indian families. This is a rare variant and has not been reported previously.

Mutations in the HFE2 (HJV) gene lead to an altered HJV protein that cannot function properly.¹³ Without adequate HJV, levels of the protein hepcidin are reduced. Hepcidin is a key hormone that regulates body iron by controlling intestinal iron absorption and release of iron from macrophage. Low levels of hepcidin result in excessive absorption of serum iron from gut, which leads to iron overload and damage to tissues and organs in the body. There have been more than 20 HJV gene mutations that have been found to cause type 2 haemochromatosis, most HJV gene mutations can cause point mutation or change in the nucleotide position and this change is responsible for alteration in one of the proteins that is used to make HJV. Commonly, glycine is replaced by valine at protein position 320 (Gly320Val). Other mutations that have been found cause a premature stop codon for making the HJV protein. Hence, as a result, very minimal amount of protein is expressed, which may be responsible for the disease. The disease causing mutation in our patient is a novel mutation due to a nucleotide change in G1006 T in exon 4 of HFE2 (HJV) gene. A nonsense mutation is occurring, which is leading to premature truncation of protein.

Findings of PH in two patients of DCMP from India have important implications. Being a reversible condition,^{12 14} PH should be suspected in such patients with DCMP especially if other clinical manifestations such as bronze pigmentation of skin, diabetes, liver cirrhosis and infertility are also present. A high index of suspicion is required and screening by inexpensive and easily available tests such as serum ferritin and transferrin saturation would be helpful. Since prevalence of PH is quite low in India, genetic analysis should only be done if serum ferritin and transferrin saturation levels are high. PH is diagnosed if biallelic mutation in causative genes is detected in patient with iron overload and other secondary causes have been ruled out.¹⁵ It is important to emphasise that mere detection of genetic mutation does not amount to diagnosis of PH. The 63D mutation is frequently found in Indian patients but its role in causing iron overload is not established.^2–5 Studies have also shown that certain mutations can affect serum ferritin concentration in general population but do not lead to sequelae of iron overload.^{16 17} Hence, correlation of genotype and phenotype is a must prerequisite for diagnosis of PH.

It is important to suspect and investigate PH in Indian patients since cardiomyopathy due to PH is reported to be reversible with phlebotomy and iron chelation therapy. Screening of family members will also provide opportunity to diagnose them in early stages and prevent the sequelae of iron overload.

Clearly, analysis of non-HFE mutations should be considered in Asian population.

Learning points.

• Primary haemochromatosis is rare but reversible cause of dilated cardiomyopathy.

• Though rare in Asian subcontinent, it should always be suspected especially if other clinical manifestations such as bronze pigmentation of skin, diabetes, liver cirrhosis and infertility are also present.

• HFE mutation being rare, analysis of non-HFE mutations should be considered in Asian population.