Lipoprotein (a): Its Role in Childhood Thromboembolism

Ulrike Nowak-Go¨ttl, MD; Ottfried Debus, MD; Martina Findeisen, MD; Reiner Kassenbo¨hmer, MD; Hans Georg Koch, MD; Harmut Pollmann, MD; Christiane Postler, MD; Peter Weber, MD; and Heinrich Vielhaber, MD

ABSTRACT. Purpose. Elevated lipoprotein (a) [LP ous sites. We used a commercially available en- (a)] concentrations are independent risk factors of cor- zyme-linked immunosorbent assay to measure Lp onary heart disease or stroke in young adults. To clar- (a) in a population of children with arterial or ify its role in childhood thromboembolism, Lp (a) was venous thrombosis. measured in 72 children with thromboembolism. Methods. In addition to Lp (a), defects of the protein C anticoagulant system, antithrombin, and antiphospho- METHODS lipid antibodies were investigated in children with arte- Seventy-two infants and children aged from birth to 18 years ؍ ؍ rial (n 36) or venous (n 36) thrombosis. consecutively recruited between 1992 and 1996 and primarily Results. Enhanced Lp (a) >50 mg/dL was diagnosed treated for arterial (n ϭ 36) or venous (n ϭ 36) thrombosis were in 8 out of 36 children with arterial and 5 out of 36 enrolled in this study. In the majority of cases arterial throm- patients with venous thrombosis. Of the 72 children, 25 bosis occurred in the central nervous system. Sixteen of 36 showed the factor V Leiden mutation, 10 showed protein infants developed embolic stroke or multiple thrombosis in the C deficiency, 2 showed antithrombin deficiency, and 4 neonatal period (attributable to the uncertainty in differentiat- showed primary antiphospholipid syndrome. Three chil- ing between embolic and local stroke in the majority of cases dren with increased Lp (a) were heterozygous for the investigated, all children with initial symptoms of stroke were factor V Leiden mutation, and 1 girl showed additional categorized in the arterial group). In addition, 11 children Ͼ1 year of age suffered an ischemic embolic, local, or lacunar protein C deficiency. stroke. Left intracardial thrombus formation was diagnosed in Conclusions. Data of this study indicate that in- 4 of 36 patients, the femoral artery was occluded in two chil- creased concentrations of Lp (a) play an important role in dren and aortic thrombosis was found in two infants. Venous childhood thrombosis. Pediatrics 1997;99(6). URL: http:// thromboses were found in the femoral vein (n ϭ 10), renal veins www.pediatrics.org/cgi/content/full/99/6/e11; childhood (n ϭ 8), superior caval vein (n ϭ 6), central nervous system (n ϭ thrombosis, lipoprotein (a), factor V Leiden, protein C. 7), and portal vein (n ϭ 5), respectively. In the majority of cases, underlying diseases triggering the thromboembolic event were diagnosed. As in previous reports, asphyxia, systemic ABBREVIATIONS. Lp (a), lipoprotein (a); LDL, low-density li- infections, dehydration, congenital heart disease, and central poprotein; apo, apolipoprotein. lines were commonly associated with the vascular occlusion reported.15–19 Fasting venous blood samples for coagulation studies were Lipoprotein (a) [Lp (a)] is a cholesterol-rich plasma obtained in the acute phase of the vascular accident and at least 6 lipoprotein with a lipid composition similar to that of months after the thrombotic episode when the children were free of anticoagulant medication. In infants and children with sus- low-density lipoproteins (LDL). The protein compo- pected inherited thrombophilia the final diagnosis was made sition is different from that of LDL, consisting of two when DNA-based assays confirmed the diagnosis (Arg506 to Gln major proteins, apolipoprotein (apo) B and apo (a).1,2 mutation of the factor V gene) or when repeatedly measured Lp (a) levels vary from person to person but are plasma concentrations were outside the age-appropriate reference range and family screening confirmed the suspected inherited genetically determined as a dominant trait, mini- 20–22 3,4 coagulation defect. Although the mean Ϯ 2 standard deviation mally affected by race, age, and sex. Numerous of the plasma values in the control children was 25 mg/dL, we groups agree in their findings that individuals with chose the markedly elevated cut-off level of Lp (a) Ͼ50 mg/dL increased concentrations of Lp (a) have a higher risk (2 ϫ 25 mg/dL) according to Margaglione et al12 in the present of premature coronary heart disease,5–7 unrelated to study. In addition, bearing in mind the importance of Lp (a) as a risk factor of familial thrombophilia, family data are included in the remaining lipoproteins. In addition, the risk of this report. 3,8–12 stroke as well as for restenosis after coronary Blood samples were drawn from a peripheral vein into pre- artery bypass surgery13,14 correlates highly with in- marked 3-mL plastic tubes (citrate 3.8%/blood 1:10; Saarstedt, creased Lp (a) concentrations. Little is known, how- Nu¨mbrecht, Germany), immediately placed on iced water and ever, about the relation between increased Lp (a) centrifuged at 4°C at 3000 g for 20 minutes. Platelet-poor plasma was snap-frozen and stored in plastic tubes at Ϫ70°C. Lp (a) concentrations and childhood thrombosis at vari- concentrations were measured with the enzyme-linked immu- nosorbent assay technique (COALIZA Lp (a): Chromogenix, Mo¨lndal, Sweden). The detection limit was .5 mg/dL and Lp (a) From the Department of Paediatrics, University Hospital, Mu¨nster, Ger- was quantified between 1 and 100 mg/dL. In addition, the factor many. V Leiden mutation (DNA prepared from ethylenediamine-tet- Received for publication Sep 17, 1996; accepted Feb 7, 1997. raacetic acid blood), factor V, protein C, protein S, antithrombin, Reprint requests to (U.N.-G.) Westfa¨lische Wilhelms-Universita¨t, Paediatric and antiphospholipid antibodies (immunoglobulin M/immuno- Haematology and Oncology, Albert-Schweitzer-Str. 33, D-48149 Mu¨nster, globulin G) were measured as described earlier.23 Germany. Calculations of median and ranges and nonparametric statistics PEDIATRICS (ISSN 0031 4005). Copyright © 1997 by the American Acad- (Wilcoxon-Mann-Whitney U test) were performed with the Apple emy of Pediatrics. computer Stat view program. http://www.pediatrics.org/cgi/content/full/99/6/Downloaded from www.aappublications.org/newse11 by guest onPEDIATRICS September 26, 2021 Vol. 99 No. 6 June 1997 1of3 TABLE 1. Incidence of Genetic Risk Factors for Thrombophilia in Children With Arterial or Venous Thromboembolism Arterial Thrombosis VenousThrombosis (n ϭ 36) (n ϭ 36) Genetic risk factors 21/36 (58 %) 29/36 (80 %) Lipoprotein (a) 8/36 (22 %) 5/36 (14 %) Factor V Leiden 11/36 (30 %) 14/36 (38 %) Protein C deficiency type I 2/36 (5.5%) 8/36 (22 %) Antithrombin deficiency type I 0/36 2/36 (5.5%)

TABLE 2. Lp (a) Concentration, Thrombus Location, and Affected Family Members in Children With Familially Increased Lp(a) and Thromboembolism Patient Location Lp (a) Additional Genetic Affected Family Lp (a): mg/dL mg/dL Risk Member Family Member Female, neonate Arterial 70 Grandparent NA* Male, neonate Arterial 145 Factor V Leiden Grandparent NA Male, 5 mo Arterial 70 Father 90 Male, 3 y Arterial 110 Father, grandparent 80/120 Male, 5 y Arterial 90 Mother 85 Male, 6 y Arterial 80 Female, 8 y Arterial 90 Factor V Leiden Grandparent NA Female, 13 y Arterial 85 Protein C deficiency Grandparent 120 Male, neonate Venous 90 Male, 3 y Venous 65 Father 80 Male, 4 y Venous 92 Grandparents NA Male, 10 y Venous 165 Mother 150 Male, 13 y Venous 98 Factor V Leiden Father, grandparent 120/150 *NAϭNot available.

RESULTS tion (n ϭ 6), stroke (n ϭ 4), or venous thrombosis Table 1 shows the overall distribution of genetic (n ϭ 1) (Table 2). risk factors for familial thrombophilia in children No factor V or protein S deficiency was diagnosed with arterial and venous thrombosis. Eight of 36 in the population studied. (22%) patients with arterial vascular insults and 5 of 36 (14%) with venous thrombosis showed Lp (a) DISCUSSION concentrations Ͼ50 mg/dL. In addition, 244 age- Data of this study indicate that 58% of children and sex-matched healthy controls showed signifi- with arterial thrombosis and 80% of children with cantly lower (P Ͻ .001) median (range) Lp (a) venous thrombosis had genetic risk factors of famil- plasma values of 7 mg/dL (0 to 39) compared with ial thrombophilia. Besides inherited defects in the 15 mg/dL (0 to 165) in children with venous protein C anticoagulant pathway, recently reported thrombosis, and 15 mg/dL (0 to 145) in patients in a smaller group of children,23 increased concentra- with arterial vascular insults, respectively. How- tions of Lp (a) play an important role in the etiology ever, median (range) Lp (a) concentrations in in- of childhood thromboembolism. fants and children with venous vascular occlusion Lp (a) was first described in human plasma by were no different from Lp (a) values in the arterial Berg as a genetic variant of ␤-lipoprotein.24 Lp (a) group. With special regard to the markedly ele- levels are reported to be regulated by a gene located vated cut-off level of Ͼ50 mg/dL chosen in this on the long arm of chromosome 6 close to the gene study, single patient values are given in Table 2.12 for plasminogen. Complementary DNA sequencing However, if we had chosen mean Ϯ 2SDLp(a) of human apo (a) showed it to be closely homologous values of the control children, the vascular acci- with plasminogen.25 This fact is assumed to provide dent would also have been classified as Lp (a)- a direct link between thrombogenesis and atheroscle- related in 5 of the remaining 28 patients (arterial) rosis.26,27 In addition, it has been speculated that high and 2 of 31 in the venous group. plasma Lp (a) levels might also be a marker of the In addition, 25 of the 72 children showed the early presence of atherosclerotic lesions at extracoro- factor V Leiden mutation, 10 protein C type I de- nary sites.28 ficiency, and two antithrombin type I deficiency. Besides increased Lp (a) levels in children with Four of the 72 children showed primary antiphos- thrombosis, 11 of 13 patients with thrombosis and Lp pholipid syndrome. Three children with increased (a) Ͼ50 mg/dL in this study had a positive family Lp (a) were heterozygous for the factor V Leiden history of early myocardial infarction, stroke, or ve- mutation, and one girl showed an additional pro- nous thrombosis. These findings confirm literature tein C deficiency (Table 2). Eleven of 13 patients data claiming that increased levels of Lp (a) in in- with thrombosis and Lp (a) Ͼ50 mg/dL had a fancy and childhood were significantly associated positive family history of early myocardial infarc- with thromboembolism in the patients’ parents or

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Downloaded from www.aappublications.org/news by guest on September 26, 2021 Lipoprotein (a): Its Role in Childhood Thromboembolism Ulrike Nowak-Göttl, Ottfried Debus, Martina Findeisen, Reiner Kassenböhmer, Hans Georg Koch, Harmut Pollmann, Christiane Postler, Peter Weber and Heinrich Vielhaber Pediatrics 1997;99;e11 DOI: 10.1542/peds.99.6.e11

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