Idiopathic infantile arterial calcification: clinical presentation, therapy and long-term follow-up

Myocardial infarction and narrowed peripheral arterial vessels secondary to generalised arterial calcification syndrome in a two-month-old girl

Generalised arterial calcification of infancy, an autosomal recessive disorder characterised by abnormal calcification of medium and large-sized arteries, represents a rare cause of dilated cardiomyopathy. We present the case of a two-month-old girl diagnosed posthumously with dilated cardiomyopathy. Studies suggest that early initiation of treatment can improve prognosis in generalised arterial calcification of infancy, so clinicians should be alert to the condition, especially in patients displaying generalised narrowing of medium and large-sized arteries.

A previously healthy 3-year-old female with hypertension, proteinuria, and hypercalciuria

A 3-year-old female patient with no significant medical history presented to her pediatrician with foamy urine. Initial testing revealed moderate proteinuria on qualitative testing, although she was incidentally noted to have severe hypertension (240/200 mmHg). Physical examination of the carotid and femoral areas revealed significant systolic vascular murmurs. Labs showed elevated serum creatinine, hypokalemia, metabolic alkalosis, elevated renin and aldosterone and hypercalciuria. Echocardiography identified ventricular hypertrophy. Computed tomography (CT) of the abdomen and magnetic resonance angiography of the head showed multiple tortuous or interrupted arteries and multiple calcifications in the renal sinus area. B-mode ultrasonography suggested thickening of the carotid and femoral artery walls, with numerous spotted calcifications. Genetic testing revealed that ABCC6 had a complex heterozygous mutation (exon 24: c.3340C > T and intron 30: c.4404-1G > A). Our panel of experts reviewed the evaluation of this patient with hypertension, proteinuria, hypercalciuria, and vascular abnormalities as well as the diagnosis and appropriate management of a rare disease.

Natural history of ENPP1 deficiency: Nationwide Turkish Cohort Study of autosomal-recessive hypophosphataemic rickets type 2

OBJECTIVE

Autosomal-recessive hypophosphataemic rickets type 2 (ARHR2) is a rare disease that is reported in survivors of generalized arterial calcification of infancy (GACI).

DESIGN, PATIENTS AND MEASUREMENT

The objective of this study was to characterize a multicenter paediatric cohort with ARHR2 due to ectonucleotide pyrophosphatase/phosphodiesterase family member 1 (ENPP1) deficiency and with a diagnosis of GACI or GACI-related findings. The clinical, biochemical and genetic characteristics of the patients were retrospectively retrieved.

RESULTS

We identified 18 patients from 13 families diagnosed with ARHR2. Fifteen of the patients had an ENPP1 variation confirmed with genetic analyses, and three were siblings of one of these patients, who had clinically diagnosed hypophosphataemic rickets (HRs) with the same presentation. From nine centres, 18 patients, of whom 12 (66.7%) were females, were included in the study. The mean age at diagnosis was 4.2 ± 2.2 (1.6-9) years. The most frequently reported clinical findings on admission were limb deformities (66.6%) and short stature (44.4%). At diagnosis, the mean height SD was -2.2 ± 1.3. Five of the patients were diagnosed with GACI in the neonatal period and treated with bisphosphonates. Other patients were initially diagnosed with ARHR2, but after the detection of a biallelic variant in the ENPP1 gene, it was understood that they previously had clinical findings associated with GACI. Three patients had hearing loss, and two had cervical fusion. After the treatment of HRs, one patient developed calcification, and one developed intimal proliferation.

CONCLUSION

ARHR2 represents one manifestation of ENPP1 deficiency that usually manifests later in life than GACI. The history of calcifications or comorbidities that might be associated with GACI will facilitate the diagnosis in patients with ARHR2, and patients receiving calcitriol and phosphate medication should be carefully monitored for signs of calcification or intimal proliferation.

Severe early-onset manifestations of generalized arterial calcification of infancy (mimicking severe coarctation of the aorta) with ABCC6 gene variant - Case report and literature review

Introduction

Generalized arterial calcification of infancy (GACI) is a rare cause of infantile heart failure and systemic hypertension with a poor prognosis, characterized by extensive calcification and proliferation of the intimal layer of large and medium sized arteries.

Case report

We present the first case report of successful surgical treatment of severe aortic arch obstruction by calcified plaques mimicking severe coarctation of the aorta and the outcome (of bisphosphonate therapy) in a newborn with GACI. Furthermore, we report the identification of a variant in ATP Binding Cassette Subfamily C, Member 6 (ABCC6) gene, possibly associated with severe early-onset manifestations of GACI.

Conclusion

This case report highlights the importance of considering GACI in an infant with heart failure, systemic hypertension, and evidence of increased echogenicity of the arterial vessels. We noted the favorable outcome in improving the aortic calcification in our patient after surgical treatment and bisphosphonates therapy. Early diagnosis and treatment improve the long-term prognosis. A better understanding of this rare genetic disease could lead to new therapeutic strategies.

Longitudinal assessment of vascular calcification in generalized arterial calcification of infancy

BACKGROUND

Generalized arterial calcification of infancy (GACI), also known as idiopathic infantile arterial calcification, is a very uncommon genetic disorder characterized by calcifications and stenoses of large- and medium-size arteries that can lead to end-organ damage.

OBJECTIVE

To describe changes in imaging findings in 10 children with GACI at a single institution from 2010 to 2021.

MATERIALS AND METHODS

In this retrospective study we reviewed initial and follow-up body imaging in children with genetic confirmation of GACI at our hospital. All initial images were analyzed for the presence and distribution of arterial calcifications, stenoses and wall thickening/irregularity within the chest, abdomen and pelvis. We compared available follow-up studies to the initial imaging findings. We extracted clinical information including prenatal and postnatal treatment from the children's medical records.

RESULTS

We evaluated 10 children (five boys) with a diagnosis of GACI. Median age at first body imaging was 8 days (range: 1 day to 5 years). Six children were identified prenatally and four postnatally. Postnatal presentation included cardiac failure, seizures and hypertension. Images in newborns (n = 8) most commonly showed diffuse arterial calcifications (6/8; 75%), while stenoses were less common (2/8; 25%) during this period. Two children were diagnosed after the neonatal period - one in infancy and one during childhood. In total, half the children (5/10; 50%) had arterial stenoses - three cases visualized at first imaging and two identified on follow-up images during infancy. Stenoses had completely resolved in one child (1/5; 20%) at last follow-up. Eight children received prenatal or postnatal treatment or both. All children who received both prenatal and postnatal treatment (n = 4) had completely resolved calcifications at last follow-up.

CONCLUSION

Children with GACI might have characteristic vascular calcifications at birth that raise the suspicion of this disease. Arterial calcifications decrease or disappear spontaneously or after treatment, but arterial stenoses usually persist. Calcifications and arterial stenoses can be easily identified and followed with non-contrast CT and CT angiography.

Should We Be Screening for Ischaemic Heart Disease Earlier in Childhood?

Ischaemic heart disease is the most common cause of death in males and the second in the female gender. Yet we often only focus on identification and treatment of this foremost cause of death in adulthood. The review asks the question what form of coronary disease do we encounter in childhood, what predisposing factors give rise to atherosclerosis and what strategies in childhood could we employ to detect and reduce atherosclerosis development in later life.

Generalized Arterial Calcification of Infancy (GACI): Optimizing Care with a Multidisciplinary Approach

It is very unusual to see evidence of arterial calcification in infants and children, and when detected, genetic disorders of calcium metabolism should be suspected. Generalized arterial calcification of infancy (GACI) is a hereditary disease, which is characterized by severe arterial calcification of medium sized arteries, mostly involving the media with marked intimal proliferation and ectopic mineralization of the extravascular tissues. It is caused by inactivating variants in genes encoding either ENPP1, in a majority of cases (70–75%), or ABCC6, in a minority (9–10%). Despite similar histologic appearances between ENPP1 and ABCC6 deficiencies, including arterial calcification, organ calcification, and cardiovascular calcification, mortality is higher in subjects carrying the ENPP1 versus ABCC6 variants (40% vs 10%, respectively). Overall mortality in individuals with GACI is high (55%) before the age of 6 months, with 24.4% dying in utero or being stillborn. Rare cases show spontaneous regression with age, while others who survive into adulthood often manifest musculoskeletal complications (osteoarthritis and interosseous membrane ossification), enthesis mineralization, and cervical spine fusion. Despite recent advances in the understanding of the genetic mechanisms underlying this disease, there is still no ideal therapy for the resolution of vascular calcification in GACI. Although bisphosphonates with anti-calcification properties have been commonly used for the treatment of CAGI, their benefit is controversial, with favorable results reported at one year and questionable benefit with delayed initiation of treatment. Enzyme replacement therapy with administration of recombinant form of ENPP1 prevents calcification and mortality, improves hypertension and cardiac function, and prevents intimal proliferation and osteomalacia in mouse models of ENPP1 deficiency. Therefore, newer treatments targeting genes are on the horizon. In this article, we review up to date knowledge of the understanding of GACI, its clinical, pathologic, and etiologic understanding and treatment in support of more comprehensive care of GACI patients.

Case Report: A Novel Genetic Mutation Causes Idiopathic Infantile Arterial Calcification in Preterm Infants

Idiopathic infantile arterial calcification (IIAC), also known as generalized arterial calcification of infancy (GACI), is a heritable ectopic mineralization disorder that results in diffuse arterial calcifications and or stenosis, which are attributed to mutations in the ENPP1 gene. In this case study, we report the development of IIAC in a 2-month-old male preterm infant. The patient presented with severe hypertension and seizures, which revealed diffused calcifications and c.130C > T and c.1112A > T mutations in the ENPP1 gene. With biphosphonate, antihypertensive, and control epilepsy therapy, his blood pressure was maintained at 110–120/50–60 mmHg. Intellectual motor development retardation was anticipated in this patient. To the best of our knowledge, this is the first case in which a novel c.130C > T mutation in the ENPP1 gene has been identified, and the administration of bisphosphonates to patients with IIAC has been assessed.

Hereditary Disorders of Cardiovascular Calcification

Arterial calcification is a common phenomenon in the elderly, in patients with atherosclerosis or renal failure and in diabetes. However, when present in very young individuals, it is likely to be associated with an underlying hereditary disorder of arterial calcification. Here, we present an overview of the few monogenic disorders presenting with early-onset cardiovascular calcification. These disorders can be classified according to the function of the respective disease gene into (1) disorders caused by an altered purine and phosphate/pyrophosphate metabolism, (2) interferonopathies, and (3) Gaucher disease. The finding of arterial calcification in early life should alert the clinician and prompt further genetic work-up to define the underlying genetic defect, to establish the correct diagnosis, and to enable appropriate therapy.

Generalized Arterial Calcification of Infancy: New Insights, Controversies, and Approach to Management

PURPOSE OF REVIEW

This review summarizes current understanding of generalized arterial calcification of infancy (GACI), emphasizing pathophysiology, clinical presentation, and approaches and controversies in management.

RECENT FINDINGS

Identification of causative ENPP1 mutations revealed that GACI arises from deficiencies in inorganic pyrophosphate (leading to calcifications) and adenosine monophosphate (leading to intimal proliferation). Identification of genotypic and phenotypic overlap with pseudoxanthoma elasticum and autosomal recessive hypophosphatemic rickets further advanced understanding of GACI as a complex, multisystemic disease. Clinical data is limited to small, retrospective samples; it is therefore unknown whether commonly used medications, such as bisphosphonates and hypophosphatemia treatment, are therapeutic or potentially harmful. ENPP1-Fc replacement represents a promising approach warranting further study. Knowledge gaps in natural history place clinicians at high risk of assigning causality to interventions that are correlated with changes in clinical status. There is thus a critical need for improved natural history studies to develop and test targeted therapies.

Skeletal abnormalities secondary to antenatal etidronate treatment for suspected generalised arterial calcification of infancy

Background

Generalised arterial calcification of infancy (GACI) is a rare disorder characterised by the deposition of hydroxyapatite crystals within the vessel walls. It is associated with a high mortality rate. Bisphosphonates have been used with some success in the treatment of GACI. However, there is a paucity of data on the antenatal use of bisphosphonates for GACI. In this paper, we report development of the skeletal changes suggestive of hypophosphatasia (HPP) in an infant with GACI, whose mother was treated with etidronate during pregnancy.

Case report

A Caucasian infant boy had a suspected antenatal diagnosis of GACI based on the findings suggestive of calcification of the annulus of the tricuspid valve and wall of the right ventricular (RV) outflow tract and main pulmonary artery on foetal echocardiography and the genetic analysis which showed a pathogenic heterozygous mutation in ABCC6. Based on these findings, mother was started on etidronate treatment from 26 weeks of gestation. A healthy male baby was delivered at 38 weeks of gestation. Initial postnatal echocardiogram on day 1 of life was normal with good biventricular function; subtle changes suggestive of microcalcifications were detected on the CT angiography. Serum calcium, phosphate, alkaline phosphatase and renal profile were normal. Further, the serum inorganic pyrophosphate (PPi) level was significantly low. Skeletal changes suggestive of HPP were seen on the radiographs. The baby developed cardiac dysfunction on day 4 of life with evidence of ischaemic changes on electrocardiogram (ECG).Treatment with etidronate was started in view of probable evolving coronary calcifications. Despite treatment with cardiac supportive measures and bisphosphonate, he succumbed to death in the third week of life.

Discussion

We believe, this is the first report of skeletal changes suggestive of HPP, arising secondary to antenatal etidronate (first generation bisphosphonate) used for the treatment of suspected GACI due to a heterozygous ABCC6 mutation.

Clinical and Biochemical Phenotypes in a Family With ENPP1 Mutations

Inactivating mutations of the ENPP1 gene are associated with generalized arterial calcification of infancy (GACI) and less often autosomal-recessive hypophosphatemic rickets type 2 (ARHR2). We aimed to investigate the spectrum of phenotypes in a family with monoallelic and biallelic mutations of ENPP1 after identification through whole exome sequencing of a 54-year-old female with biallelic mutation of ENPP1, c.323G > T; p.Cys108Phe and c.1441C > T; p.Arg481Trp. Including the proband, 2 subjects had biallelic mutations, 5 had monoallelic mutations, and 2 had no mutation of ENPP1. The maternal mutation, a known pathogenic variant associated with GACI, was found in 3 subjects with monoallelic mutations, while the paternal mutation, which was not previously reported, was present in 2 subjects with monoallelic mutations. Both subjects with biallelic mutations had bowing of bilateral femurs, periarticular mineral deposition, normocalcemic primary hyperparathyroidism with multigland parathyroidectomy, increased carotid intima-media thickness, and enthesopathy was also noted in one subject. Intact FGF23 was elevated in both subjects with biallelic mutations, while C-terminal FGF23 was only elevated in one and PPi was reduced in one. Subjects with monoallelic mutations did not have periarticular calcifications or bone deformities. To conclude, patients with biallelic GACI causing mutations can survive well into adulthood, and despite the same biallelic ENPP1 pathogenic variants, clinical and biochemical manifestations can significantly differ, and include enthesopathy and primary hyperparathyroidism, which have not been previously described. Although carriers of monoallelic ENPP1 variants appear unaffected by classic disease manifestations, there may be subtle biochemical and clinical findings that warrant further investigation. © 2019 American Society for Bone and Mineral Research.

Novel homozygous ENPP1 mutation causes generalized arterial calcifications of infancy, thrombocytopenia, and cardiovascular and central nervous system syndrome

Generalized arterial calcifications of infancy (GACI) is caused by mutations in ENPP1. Other ENPP1-related phenotypes include pseudoxanthoma elasticum, hypophosphatemic rickets, and Cole disease. We studied four children from two Bedouin consanguineous families who presented with severe clinical phenotype including thrombocytopenia, hypoglycemia, hepatic, and neurologic manifestations. Initial working diagnosis included congenital infection; however, patients remained without a definitive diagnosis despite extensive workup. Consequently, we investigated a potential genetic etiology. Whole exome sequencing (WES) was performed for affected children and their parents. Following the identification of a novel mutation in the ENPP1 gene, we characterized this novel multisystemic presentation and revised relevant imaging studies. Using WES, we identified a novel homozygous mutation (c.556G > C; p.Gly186Arg) in ENPP1 which affects a highly conserved protein domain (somatomedin B2). ENPP1-associated genetic diseases exhibit phenotypic heterogeneity depending on mutation type and location. Follow-up clinical characterization of these families allowed us to revise and detect new features of systemic calcifications, which established the diagnosis of GACI, expanding the phenotypic spectrum associated with ENPP1 mutations. Our findings demonstrate that this novel ENPP1 founder mutation can cause a fatal multisystemic phenotype, mimicking severe congenital infection. This also represents the first reported mutation affecting the SMB2 domain, associated with GACI.

[Persistent hypertension for two months in a preterm infant]

A boy aged 2 months (born at 36 weeks of gestation) was admitted due to cough and dyspnea. After admission, he was found to have persistent hypertension, proteinuria, and persistent convulsion, and imaging examination showed extensive calcification of the aorta and major branches and stenosis of local lumens of the abdominal aorta and the right renal artery with increased blood flow velocity. The boy was admitted during the neonatal period due to wet lung and pulmonary arterial hypertension and was found to have hypertension and proteinuria. High-throughput whole-exome sequencing was performed and found two compound heterozygous mutations in the ENPP1 gene from his parents, c.130C>T (p.Q44X) and c.1112A>T (p.Y371F). c.130C>T was a nonsense mutation, which could cause partial deletion of protein from 44 amino acids, and was defined as a primary pathogenic mutation. c.1112A>T was a missense mutation which had been reported as a pathogenic mutation associated with idiopathic infantile arterial calcification (IIAC). Therefore, he was diagnosed with IIAC. He was given phosphonate drugs, antihypertensive drugs, anticonvulsion treatment, and respiratory support. Blood pressure was maintained at the upper limit of normal value. There was no deterioration of arterial calcification. It is concluded that IIAC should be considered for infants with persistent hypertension and extensive vascular calcification, and imaging and genetic examinations should be performed as early as possible to make a confirmed diagnosis.

Increased activity of TNAP compensates for reduced adenosine production and promotes ectopic calcification in the genetic disease ACDC

ACDC (arterial calcification due to deficiency of CD73) is an autosomal recessive disease resulting from loss-of-function mutations in NT5E, which encodes CD73, a 5'-ectonucleotidase that converts extracellular adenosine monophosphate to adenosine. ACDC patients display progressive calcification of lower extremity arteries, causing limb ischemia. Tissue-nonspecific alkaline phosphatase (TNAP), which converts pyrophosphate (PPi) to inorganic phosphate (Pi), and extracellular purine metabolism play important roles in other inherited forms of vascular calcification. Compared to cells from healthy subjects, induced pluripotent stem cell-derived mesenchymal stromal cells (iMSCs) from ACDC patients displayed accelerated calcification and increased TNAP activity when cultured under conditions that promote osteogenesis. TNAP activity generated adenosine in iMSCs derived from ACDC patients but not in iMSCs from control subjects, which have CD73. In response to osteogenic stimulation, ACDC patient-derived iMSCs had decreased amounts of the TNAP substrate PPi, an inhibitor of extracellular matrix calcification, and exhibited increased activation of AKT, mechanistic target of rapamycin (mTOR), and the 70-kDa ribosomal protein S6 kinase (p70S6K), a pathway that promotes calcification. In vivo, teratomas derived from ACDC patient cells showed extensive calcification and increased TNAP activity. Treating mice bearing these teratomas with an A2b adenosine receptor agonist, the mTOR inhibitor rapamycin, or the bisphosphonate etidronate reduced calcification. These results show that an increase of TNAP activity in ACDC contributes to ectopic calcification by disrupting the extracellular balance of PPi and Pi and identify potential therapeutic targets for ACDC.

Treatment of hypophosphatemic rickets in generalized arterial calcification of infancy (GACI) without worsening of vascular calcification

Patients with generalized arterial calcification of infancy (GACI) develop vascular calcifications early in life. About half of them die within the first 6 months despite optimal medical care. A subset of those who survive eventually develop hypophosphatemic rickets. Since hypophosphatemia and hyperphosphaturia have been previously associated with increased survival in GACI patients, physicians often avoid phosphate repletion as treatment for rickets. As a consequence, GACI patients develop severe rachitic complications such as short stature and skeletal deformities. It appears that the recognition of hypophosphatemia later in life in some GACI patients is a consequence of having survived the first few months of life, and not the cause of their survival per se. Here, we report the long-term follow-up of a GACI patient who was phosphate-repleted for his rickets for more than 7 years without worsening of vascular calcification.

Idiopathic Arterial Calcification of Infancy: Case Report

Idiopathic arterial calcification of infancy is a rare autosomal recessive disease, characterized by deposition of calcium along the internal elastic membrane of arteries, accompanied by fibrous thickening of the intima which causes luminal narrowing. Here we are reporting a case of idiopathic arterial calcification of infancy in a Saudi female newborn of non-consanguineous pregnant woman who had polyhydramnios. The newborn baby had severe respiratory distress, systemic hypertension and persistent pulmonary hypertension of newborn. She was admitted to Neonatal Intensive Care Unit, where she was ventilated and proper treatment was provided. Molecular genetic testing was positive for mutations of ectonucleotide pyrophosphatase/phosphodiesterase1 gene which is reported in 80% of cases of Idiopathic arterial calcification of infancy. The baby died at about 5 month of age because of myocardial ischemia and cardiorespiratory arrest. Idiopathic Arterial Calcification of Infancy should be considered in any newborn who presented with persistent pulmonary hypertension of newborn, severe systemic hypertension and echogenic vessels on any radiological study. Calcifications of large and medium-sized arteries are important diagnostic finding.

From variome to phenome: Pathogenesis, diagnosis and management of ectopic mineralization disorders

Ectopic mineralization - inappropriate biomineralization in soft tissues - is a frequent finding in physiological aging processes and several common disorders, which can be associated with significant morbidity and mortality. Further, pathologic mineralization is seen in several rare genetic disorders, which often present life-threatening phenotypes. These disorders are classified based on the mechanisms through which the mineralization occurs: metastatic or dystrophic calcification or ectopic ossification. Underlying mechanisms have been extensively studied, which resulted in several hypotheses regarding the etiology of mineralization in the extracellular matrix of soft tissue. These hypotheses include intracellular and extracellular mechanisms, such as the formation of matrix vesicles, aberrant osteogenic and chondrogenic signaling, apoptosis and oxidative stress. Though coherence between the different findings is not always clear, current insights have led to improvement of the diagnosis and management of ectopic mineralization patients, thus translating pathogenetic knowledge (variome) to the phenotype (phenome). In this review, we will focus on the clinical presentation, pathogenesis and management of primary genetic soft tissue mineralization disorders. As examples of dystrophic calcification disorders Pseudoxanthoma elasticum, Generalized arterial calcification of infancy, Keutel syndrome, Idiopathic basal ganglia calcification and Arterial calcification due to CD73 (NT5E) deficiency will be discussed. Hyperphosphatemic familial tumoral calcinosis will be reviewed as an example of mineralization disorders caused by metastatic calcification.

Prenatal ultrasonographic diagnosis of generalized arterial calcification of infancy

A healthy 19-year-old nulliparous pregnant woman was referred to our clinic because of fetal pericardial effusion and ascites. The sonographic examination performed at 28 weeks' gestation revealed scalp edema, severe skin edema, bilateral hydrocele, ascites, and pleural and pericardial effusion. Fetal echocardiographic examination showed that both ventricles were dilated with severely depressed contractility. The aortic annulus, ascending aorta, aortic arch, descending aorta, common iliac arteries, main pulmonary artery, tricuspid valve, and mitral chordae tendinae were hyperechogenic. Right ventricular outflow tract was narrow with decreased blood flow. There was tricuspid and mitral valve regurgitation and tricuspid valve stenosis. On the basis of these findings, we made the diagnosis of generalized arterial calcification, which is characterized by extensive calcification of internal elastic lamina and intimal proliferation of medium-sized and large arteries. This diagnosis was confirmed histologically after the termination of pregnancy.

Vascular calcification is dependent on plasma levels of pyrophosphate

Plasma levels of pyrophosphate, an endogenous inhibitor of vascular calcification, are reduced in end-stage renal disease and correlate inversely with arterial calcification. However, it is not known whether the low plasma levels are directly pathogenic or are merely a marker of reduced tissue levels. This was tested in an animal model in which aortas were transplanted between normal mice and Enpp1−/− mice lacking ectonucleotide pyrophosphatase phosphodiesterase, the enzyme that releases extracellular pyrophosphate. Enpp1−/− mice had very low plasma pyrophosphate and developed aortic calcification by 2 months that was greatly accelerated with a high-phosphate diet. Aortas of Enpp1−/− mice showed no further calcification after transplantation into wild type mice fed a high phosphate diet. Aorta allografts of wild type mice calcified in Enpp1−/− mice but less so than the adjacent recipient Enpp1−/− aorta. Donor and recipient aortic calcium contents did not differ in transplants between wild type and Enpp1−/− mice, demonstrating that transplantation per se did not affect calcification. Histology revealed medial calcification with no signs of rejection. Thus, normal levels of extracellular pyrophosphate are sufficient to prevent vascular calcification and systemic Enpp1 deficiency is sufficient to produce vascular calcification despite normal vascular extracellular pyrophosphate production. This establishes an important role for circulating extracellular pyrophosphate in preventing vascular calcification.

Mutations in the ABCC6 gene as a cause of generalized arterial calcification of infancy: genotypic overlap with pseudoxanthoma elasticum

Generalized arterial calcification of infancy (GACI) is an autosomal recessive disorder characterized by congenital calcification of large- and medium-sized arteries, associated with early myocardial infarction, heart failure, and stroke, and premature death. Most cases of GACI are caused by mutations in the ENPP1 gene. We first studied two siblings with GACI from a non-consanguineous family without mutations in the ENPP1 gene. To search for disease-causing mutations, we identified genomic regions shared between the two affected siblings but not their unaffected parents or brother. The ABCC6 gene, which is mutated in pseudoxanthoma elasticum (PXE), resided within a small region of homozygosity shared by the affected siblings. Sequence analysis of ABCC6 revealed that the two affected siblings were homozygous for the missense mutation p.R1314W. Subsequently, ABCC6 mutations were identified in five additional GACI families with normal ENPP1 sequences. Genetic mutations in ABCC6 in patients with PXE are associated with ectopic tissue mineralization in the skin and arterial blood vessels. Thus, our findings provide additional evidence that the ABCC6 gene product inhibits calcification under physiologic conditions and confirm a second locus for GACI. In addition, our study emphasizes the potential utility of shared homozygosity mapping to identify genetic causes of inherited disorders.

Idiopathic infantile arterial calcification: a possible cause of refractory cardiopulmonary failure in infancy

Idiopathic Infantile Arterial Calcification is a rare autosome recessive disease characterized by extensive calcification of medium and large arteries. Loss-of-function mutations in ectonucleotide pyrophosphatase/phosphodiesterase 1 gene have been described in more than 80% of the cases. Although the diagnosis is usually made at autopsy, it is possible to identify cases based on clinical presentation, radiology findings, and molecular studies. Appropriate treatment can be initiated and has been shown to successfully induce permanent remission. We report a 4-week-old neonate who initially presented with respiratory distress, heart failure, and Coxsackie B viremia suggestive of viral induced cardiomyopathy. His symptoms progressed to multiple organ failure and he eventually expired at four weeks of age. On autopsy, diffuse calcium deposition within the internal elastic lamina of medium and large arteries was identified, as well as narrowing of lumen due to myointimal proliferation. This case report will emphasize the importance of taking this rare curable disease into consideration in all cases of infants with cardiopulmonary failure.

The mystery of persistent pulmonary hypertension: an idiopathic infantile arterial calcification

BACKGROUND

Idiopathic infantile arterial calcification (IIAC) is a rare autosomal recessive disorder, characterized by wide spread calcifications in arterial walls, leading to vaso-occlusive ischaemia of multiple organs. Mortality is high, and there is no definitive treatment.

CASE PRESENTATION

A male neonate, 36+5 weeks gestation, 2.81 kg, was admitted to NICU for respiratory distress. At one hour of age, he was noted to be pale, hypoperfused, with weak pulses, a hyperdynamic precordium and a grade IV/VI pansystolic murmur. The rest of his examination was normal. A chest X-ray showed massive cardiomegaly and pulmonary oedema. An echocardiogram (ECHO) indicated moderate persistent pulmonary hypertension (PPHN) of unclear etiology. A diagnosis of Idiopathic infantile arterial calcification was made and a trial of Editronate therapy was given without success.

CONCLUSION

IIAC is a rare disorder, it should be considered whenever a neonate presents with unexplainable cardiac failure, PPHN, echogenic vessels on X-ray/ultrasound and, or concentric hypertrophic ventricles on ECHO. Serial antenatal ultrasound findings of echogenic cardiac foci should raise the suspicion of IIAC. Further studies to determine the long term effects of Editronate on vascular calcifications, disease outcome, and other treatment options are needed.

Severe skeletal toxicity from protracted etidronate therapy for generalized arterial calcification of infancy

Generalized arterial calcification (AC) of infancy (GACI) is an autosomal recessive disorder that features hydroxyapatite deposition within arterial elastic fibers. Untreated, approximately 85% of GACI patients die by 6 months of age from cardiac ischemia and congestive heart failure. The first-generation bisphosphonate etidronate (EHDP; ethane-1-hydroxy-1,1-diphosphonic acid, also known as 1-hydroxyethylidene-bisphosphonate) inhibits bone resorption and can mimic endogenous inorganic pyrophosphate by blocking mineralization. With EHDP therapy for GACI, AC may resolve without recurrence upon treatment cessation. Skeletal disease is not an early characteristic of GACI, but rickets can appear from acquired hypophosphatemia or prolonged EHDP therapy. We report a 7-year-old boy with GACI referred for profound, acquired, skeletal disease. AC was gone after 5 months of EHDP therapy during infancy, but GACI-related joint calcifications progressed. He was receiving EHDP, 200 mg/day orally, and had odynodysphagia, diffuse opioid-controlled pain, plagiocephaly, facial dysmorphism, joint calcifications, contractures, and was wheelchair bound. Biochemical parameters of mineral homeostasis were essentially normal. Serum osteocalcin was low and the brain isoform of creatine kinase and tartrate-resistant acid phosphatase 5b (TRAP-5b) were elevated as in osteopetrosis. Skeletal radiographic findings resembled pediatric hypophosphatasia with pancranial synostosis, long-bone bowing, widened physes, as well as metaphyseal osteosclerosis, cupping and fraying, and "tongues" of radiolucency. Radiographic features of osteopetrosis included osteosclerosis and femoral Erlenmeyer flask deformity. After stopping EHDP, he improved rapidly, including remarkable skeletal healing and decreased joint calcifications. Profound, but rapidly reversible, inhibition of skeletal mineralization with paradoxical calcifications near joints can occur in GACI from protracted EHDP therapy. Although EHDP treatment is lifesaving in GACI, surveillance for toxicity is crucial.

Molecular diagnosis of generalized arterial calcification of infancy (GACI)

Generalized arterial calcification of infancy (GACI) is a life-threatening disorder in young infants. Cardiovascular symptoms are usually apparent within the first month of life. The symptoms are caused by calcification of large and medium-sized arteries, including the aorta, coronary arteries, and renal arteries. Most of the patients die by 6 months of age because of heart failure. Recently, homozygous or compound heterozygous mutations for the ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) gene were reported as causative for the disorder. ENPP1 regulates extracellular inorganic pyrophosphate (PP_i), a major inhibitor of extracellular matrix calcification. A newborn was diagnosed with GACI. The infant died at the age of 7 weeks of cardiac failure and the parents were referred to Molecular Biology and Cytogenetic lab for further workup. Cytogenetics analysis was performed on the parents, which showed normal karyotypes and mutational analysis for the ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) gene was also performed. The mutational analysis showed that both father and mother of the deceased infant were heterozygous carriers of the mutation c.749C>T (p.P250L) in exon 7 of ENPP1 and it was likely, that the deceased child carried the same mutation homozygous on both alleles and died of GACI resulting from this ENPP1 mutation. The couple was counseled and monitored for the second pregnancy. Amniocentesis was performed at 15 weeks of gestation for mutational analysis of the same gene in the second pregnancy. The analysis was negative for the parental mutations. One month after the birth of a healthy infant, peripheral blood was collected from the baby and sent for reconfirmation. The results again were negative for the mutation and the baby was on 6 months follow up and no major symptoms were seen. The parents of the child benefited enormously by learning about the disease much in advance and also its risk of recurrence. The main aim of this study is to emphasize on two aspects: (i) the importance of modern molecular techniques in diagnosis such a syndrome and (2) the difficulties faced by the physician to provide appropriate diagnosis and the adequate genetic counseling to the family without molecular facilities.

Unusual cause of myocardial ischemia in an infant

Abnormal coronary artery anatomy should be ruled out in any patient with myocardial dysfunction and an abnormal electrocardiogram. The reported etiologies of infantile myocardial ischemia are abnormalities of coronary arteries, perinatal asphyxia, umbilical catheterization, and myocarditis. Generalized arterial calcification of infancy, although rare, should be considered in the differential diagnosis of infantile myocardial ischemia if coronary artery origin is found to be normal on echocardiography.

Efficacy and safety of 2-year etidronate treatment in a child with generalized arterial calcification of infancy

Generalized arterial calcification of infancy (GACI, MIM#208000) is a rare autosomal recessive disorder characterized by extensive calcifications in the media of large- and medium-sized muscular arteries. Most affected children die in early infancy because of cardiac failure. GACI is linked to mutations in the ENPP1 gene, which encodes for an enzyme that generates inorganic pyrophosphate (PP(i)), a potent inhibitor of hydroxyapatite crystal formation. Treatment with bisphosphonates, which are synthetic PP(i) analogues, has been proposed as a means of reducing arterial calcifications in GACI patients, but no formalized treatment approach exists. We report on the long-term survival of a severe case of GACI linked to a novel homozygous missense mutation c.583T/C in the ENPP1 gene, diagnosed prenatally, and treated with bisphosphonates. Intravenous disodium pamidronate (three infusions at days 8, 15, and 18 of 0.25, 0.50, and 0.50 mg/kg, respectively) was changed to oral disodium etidronate (starting dose of 20 mg/kg daily, 50 mg die) at 3 weeks of age. Although the etidronate dose was maintained at 50 mg daily in our patient (corresponding to a progressive decrease from 20 to 5 mg/kg daily), the progressive resolution of arterial calcifications seen by 3 months of age was maintained until 2 years of age. Throughout the 2-year follow-up, our patient developed mild hypophosphatemia, due to renal phosphate wasting, without clinical, biochemical, or radiological sign of rickets.

CONCLUSION

High-dose bisphosphonate therapy may not be necessary for an extended period of time in children with GACI.

Generalized Arterial Calcification of Infancy: Fatal Clinical Course Associated with a Novel Mutation in ENPP1

Generalized arterial calcification of infancy (GACI) is a rare condition characterized by arterial calcification within the internal elastic lamina associated with intimal proliferation, leading to stenosis of great and medium-sized vessels. This disease, caused by mutations in multiple exons of ENPP1, frequently results in death in infancy. Nowadays, the most promising therapeutic compounds for this rare disease are bisphosphonates. We describe a case of GACI associated with the novel mutation c.653A>T (p.D218V) in ENPP1 on both alleles. The male infant was delivered prematurely and developed heart failure, severe hypertension, and diffuse calcifications of all arterial districts. He was treated with etidronate (18 mg/kg/day); however, the clinical condition did not improve, and a resolution of calcifications was not observed. The infant died within the 6th month of life of ischemic heart failure. We conclude that even if the diagnosis of GACI is established early and bisphosphonate treatment is started early, the prognosis can be very poor.

Two cases of idiopathic infantile arterial calcification

We present the clinical course and management of two infants with idiopathic infantile arterial calcification. Both had coronary artery involvement and presented with ischaemic cardiac failure. Neither responded well to conventional therapy with inotropic agents, glyceryl trinitrate, diuretic and mechanical ventilation, nor to short-term biphosphonates. One was treated with levosimendan and extracorporeal membrane oxygenation to no avail.

Idiopathic infantile arterial calcification: a rare cause of sudden unexpected death in childhood

Unexpected child death investigation is a difficult area of forensic practice in view of the wide range of possible genetic, congenital, and acquired natural and nonnatural causes. Idiopathic infantile arterial calcification (IIAC) is a rare autosomic recessive disease usually diagnosed postmortem. Inactivating mutations of the ENPP1 gene were described in 80% of the cases with IIAC. We report a case of a 5-year-old girl submitted to a forensic autopsy due to sudden death and possible medical negligence/parents child abuse. Major alterations found (intimal proliferation and deposition of calcium hydroxyapatite around the internal elastic lamina and media of arteries; acute myocardial infarct, stenotic and calcified coronary artery; perivascular and interstitial myocardial fibrosis; and subendocardial fibroelastosis) were diagnostic of IIAC. We reviewed IIAC cases published in the English literature and highlight the importance of adequate autopsy evaluation in cases of sudden child death.

Diagnosis of perinatal stroke II: mechanisms and clinical phenotypes

INTRODUCTION

Here (and in an accompanying article dealing with definitions, differential diagnosis and registration), a structured sequential diagnostic flow is proposed to discern clinical phenotypes for perinatal stroke, including arterial ischaemic stroke (AIS), cerebral sinovenous thrombosis (CSVT) and haemorrhagic stroke.

MATERIAL AND RESULTS

For neonatal AIS, the diagnostic sequence is infection, trauma, embolism, arteriopathy, other, primary thrombosis and unclassifiable; for neonatal CSVT, the sequence is infection, trauma, venopathy, other, primary thrombosis and unclassifiable. The proposed hierarchical diagnostic flows are an initial step towards a standard for registration of the causes of neonatal stroke. Such standardization should guide attempts at prevention and intervention. An extensive literature search and study of a retrospective cohort of 134 newborn infants with stroke suggest that embolism is the most common identifiable cause for stroke in general (25%), preceding trauma (10%) and infection (8%). Other causes, such as asphyxia, acute blood loss, extracorporeal membrane oxygenation, genetic disorders or prothrombotic conditions, are seen in <5% of cases. For neonatal AIS, the presence of an embolic phenotype is 33% in this cohort. The designation unclassifiable scored 34% for the entire stroke group and 25% for neonatal AIS. Complex arterial stroke with multiple arteries involved is often seen when the underlying cause is infection, cranial trauma or embolism. One important conclusion is that a means of prevention is avoidance of embolism from thrombosis outside the brain.

CONCLUSION

To prevent the occurrence and recurrence of neonatal ischaemic stroke, clinicians must develop a standardized diagnostic approach that results in characterization of the clinical phenotype.

Prenatal diagnosis of idiopathic infantile arterial calcification with hydrops fetalis

Idiopathic infantile arterial calcification (IIAC) is a rare and nearly always fatal disorder. To date, prenatal diagnosis has been reported in fewer than 10 cases. We describe a series of three cases in which the diagnosis of IIAC was made at 23, 25 and 29 weeks' gestation. All three cases presented with a normal anatomy scan at 20 weeks' gestation with an echogenic intracardiac focus. Follow-up scans showed generalized hyperechogenicity and calcification of the walls of the large arteries, particularly the aorta and the iliac arteries. All cases developed hydrops fetalis with cardiomegaly and polyhydramnios later in gestation, resulting in intrauterine fetal death in two cases and neonatal death immediately following delivery in the third. This is the largest case series and the earliest gestational age of prenatal diagnosis of IIAC reported to date. When surveying for the disease, serial scans are important, perhaps from 20 weeks' gestation, with close examination of the iliac and aortic arteries. Detection of echogenic intracardiac focus could be an early marker in patients with a family history of the disease.

Generalized arterial calcification of infancy: treatment with bisphosphonates

BACKGROUND

A baby girl developed respiratory distress immediately after birth and required supplemental oxygen. She was born at term via lower-segment cesarean section. The parents were nonconsanguineous, and antenatal ultrasonography during the pregnancy at 18 and 32 weeks of gestation did not reveal any abnormalities. On examination at birth, no pulses were palpable; however, the baby's blood pressure was normal and no remarkable abnormalities were detected. Ultrasonography revealed widespread arterial calcification.

INVESTIGATIONS

Chest and abdominal radiography at birth and serial abdominal, renal and cardiac ultrasonography at follow-up examinations; dual-energy X-ray absorptiometry during treatment with bisphosphonates; genetic screening.

DIAGNOSIS

Generalized arterial calcification of infancy, secondary to compound, heterozygous mutations in the ENPP1 gene, pL661V and pE668K of the paternal chromosome, and pN792S in the maternal chromosome.

MANAGEMENT

Low-dose disodium pamidronate (0.1 mg/kg per week for 4 weeks), which commenced on the seventh day after birth and was changed to oral risedronate sodium (1 mg/kg per week as a single dose) at 4 weeks of age. Complete resolution of arterial calcification was seen by 3 months of age. At 12 months, ergocalciferol was added at a dose of 5,000 U daily for 6 weeks, followed by 200 U daily owing to the patient's vitamin D deficiency and elevated parathyroid hormone level. Treatment with bisphosphonates is ongoing, but is planned to be discontinued at 3 years of age. The child has remained healthy and developmentally normal.

The difficulty in diagnosing idiopathic arterial calcification of infancy, its variation in presentation, and the importance of autopsy

Idiopathic calcification of the coronary arteries is a rare hereditary condition of infancy. Complications include cardiac ischaemia, cardiac failure, and systemic hypertension. We present three patients with this condition, which in each case masqueraded as other cardiac diseases, with no indication of the specific diagnosis prior to autopsy.A 5 month old female presented with respiratory failure and hypertension and died within 24 hours of admission. All the coronary arteries were thick-walled, with narrow lumens. The aorta, great vessels, and renal arteries also showed thickening of the wall. Histology confirmed calcium in the internal elastic lamina of all vessels. The second patient was a female baby of 2 months, diagnosed with a large ventricular septal defect. She died suddenly prior to surgery. At autopsy, the orifice of the right coronary artery was reduced to a pinhole. The coronary arteries showed white patches of calcification, with associated ventricular infarction. The third patient was an 11 year old female who presented with cardiac failure, and had been diagnosed with dilated cardiomyopathy. Two weeks later, she died suddenly. The coronary arteries were patent, but firm with calcification and narrowed, with associated ventricular infarction. Our experience shows that idiopathic arterial calcification of infancy should always be considered in infants and children presenting with hypertension, cardiac failure, or sudden death.