95 (1992) 231-234 @ 1992 Elsevier Scientific Publishers Ireland, Ltd. Ail rights reserved. 0021-9150/92/$05.00 Printed and Published in Ireland
231
Atherosclerosis,
ATHERO 04874
Effective reduction of plasma LDL levels by LDL apheresis in familial defective apolipoprotein B- 100 Vincent M.G. Mahera’b, Yuri Kitanoa, Claire Neuwirtha, John J. Gallagher”, Gilbert R. Thompsona and Nicholas B. Myant” ‘MRC
Lipoprotein
Team and hDepartment
of Cardiology,
Hammersmith
Hospital,
DuCane
Road, London
WI2 OHS (UK)
(Received 13 March, 1992) (Revised, received 1 June, 1992) (Accepted 3 June, 1992)
Summary
The clinical response to long-term reduction of the plasma LDL cholesterol concentration was studied in a man with severe coronary artery disease associated with familial defective apolipoprotein B-100 (FDB). Plasma exchange repeated at 2-week intervals, combined with lipid-lowering drugs, led to remission of angina and improved exercise test performance. A similar clinical response was achieved after LDL apheresis with dextran sulphate columns repeated once every 2 weeks in combination with drug treatment. The reduction in plasma LDL cholesterol level brought about by LDL apheresis was at least as marked in the FDB patient as in 5 patients with familial hypercholesterolaemia. We conclude that FDB patients with coronary artery disease may derive clinical benefit from prolonged reduction of their plasma cholesterol levels and that LDL containing apo B-100 in which arginine at position 3500 is replaced by glutamine is removed from plasma by dextran sulphate columns as efficiently as is normal LDL.
Key words: Familial defective apolipoprotein
B-100; LDL apheresis
Introduction
Apolipoprotein B-100 (apo B-100) is the protein component of low-density lipoprotein (LDL) and is responsible for the recognition of LDL by LDL receptors. Familial defective apo B-100 (FDB) is a Corres,mw+ence to: Dr. Vincent Maher, MRC Lipoprotein Team, Hammersmith Hospital, DuCane Road, London WI2 OHS, UK. Tel.! 081-7403262; Fax: 081-7460586.
dominantly inherited abnormality of apo B-100 in which arginine at residue 3500 is replaced by glutamine [l]. This amino acid substitution decreases the binding of LDL by the LDL receptor by more than 95%, leading to hypercholesterolaemia in most FDB heterozygotes [2]. Since each LDL particle contains only one molecule of apo B100, the serum of an FDB heterozygote contains two populations of LDL particles, one with apo B encoded in the normal gene and the other with the
232
apo B variant. The hypercholesterolaemia in FDB heterozygotes is due to accumulation of defective LDL particles containing the mutant apo B-100 [31. Since many patients with FDB develop premature coronary heart disease (CHD) [4-71, it is essential to treat the hypercholesterolaemia that usually occurs in this condition. We have shown that drugs that lower the serum cholesterol level by stimulating LDL receptor activity are as effective in FDB as in familial hypercholesterolaemia (FH) [8]. However, in some patients with critically severe coronary artery disease it may be desirable to achieve very marked reductions of the plasma cholesterol level using additional methods, in order to arrest or reverse coronary atherosclerosis. In the treatment of FH, extracorporeal removal of plasma cholesterol by repeated plasma exchange has been shown to bring about a marked reduction in the serum cholesterol level [9] and to prolong life [lo]. As a means of reducing the serum cholesterol level, plasma exchange has been superseded by LDL apheresis, a procedure in which LDL and other apo B-containing lipoproteins are removed extracorporeally by selective adsorption on columns of dextran sulphate [ 1l] or
other adsorptive agents. In patients with FH (in which apo B is normal), LDL apheresis lowers the serum cholesterol level and may induce regression of coronary atherosclerosis [12], but its use in the treatment of FDB has not been reported previously. However, provided that the mutation in apo B does not affect the binding of LDL by the columns, this procedure should be as effective in FDB as in FH. In this communication we describe the response of a patient with FDB to repeated LDL apheresis. Our observations indicate that dextran-sulphate columns remove defective and normal LDL from the circulation with similar efficiency. Methods Serum lipids and lipoprotein concentrations were determined as described [7]. Serum apo B concentration was measured by an immunonephelometric method with the Beckman Immunochemistry System Analyser (ICS) (Beckman Instruments Limited, High Wycombe, UK). FDB was diagnosed by amplifying the relevant segment of the patient’s apo B gene, followed by hybridization with radioactive oligonucleotide probes [4].
I
LW cholsstemlmodid fat diet Diet 16&l Cholestyramins LlsOl 249
I
2a
Nkotinic add
4omn
Lwmtatin Simvastatin
I
8oma
1
4omp
I
mw
Plasmaexbange LDL aphemis
10 a-
a-
0 r
a2
’ a3
1 a4
’ a5
’ aa ’ a7 ’ 88 ’ a9 ’ 90
’ 91
’ 92
’
Year
Fig. 1. SerumLDL cholesterol (LDL-C) concentration in a patient (A.S.) with familial defective apolipoprotein B-100 during treatment with cholesterol-lowering drugs, plasma exchange and LDL apheresis over a 9-year period (1983-1992).
233
LDL-receptor function in the patient’s ftbroblasts in culture was assayed as described (71. Plasma exchange [9] and LDL apheresis [1 1] were carried out by methods previously described.
Clinical background The patient is a 59-year-old man. At the age of
49 he was found to have marked hyperlipidaemia (serum cholesterol 13 mmoY1; triglycerides 4.4 mmol/l), angina of effort and extensive xanthomas on the tendons of his left hand. He also had a family history of premature CHD. Initially he was given a clinical diagnosis of heterozygous FH but was later shown to have FDB with normal LDL receptor function (AS. in Table 1 of Ref. 7). His serum LDL cholesterol (LDL-C) level responded well to a low-cholesterol modified fat diet, cholestyramine and nicotinic acid (Fig. 1), although his angina persisted. An exercise test at age 52 showed 1 mm ST segment depression after 6 min on a modified Bruce protocol; coronary angiography revealed totally occluded circumflex and right coronary arteries, both of which filled retrogradely from the left anterior descending artery which had a 40% stenosis distal to the first diagonal branch. The patient who was unsuitable for coronary angioplasty was offered, but refused, coronary artery bypass surgery. In view of the severity of his coronary artery disease and of his clinical condition, it was thought essential to achieve an even greater reduction of his serum LDL level than the 50% reduction already achieved by drugs. He was therefore treated by plasma exchange once every 2 weeks, combined with cholestyramine and lovastatin (Fig. 1). While on this treatment his integrated mean serum LDL-C level between procedures fell to less than 3 mmohl. This led to the disappearance of his angina after 6 months and to improved exercise test performances. Plasma exchange was discontinued after 18 months and his drug treatment was adjusted (Fig. 1). He remained well for about 3 years after which his angina returned, though in less severe form than that prior to plasma exchange. His exercise test performance had also deteriorated during this period. His symptoms were controlled with glyceryl trinitrate. However, because the recurrence of his angina suggested progression of coronary artery disease it was
decided to supplement LDL apheresis.
his drug treatment
with
Response to LDL apheresis
LDL apheresis with twin dextran sulphate columns, performed once every 2 weeks, was begun in July 1990 and has continued until the present time. In order to determine the maximum effect of a single procedure on A.S.‘s serum LDL-C level, the levels were measured before and immediately after apheresis in a total of 10 procedures during the course of his treatment. The mean reduction in LDL-C level in the 10 procedures was 77.6% f 2%. Similar measurements were made on 5 FH heterozygotes with CHD who were concurrently undergoing LDL apheresis (3 males and 2 females, mean age 47 years). In a total of 57 procedures the mean value (64.1% f 6%) was significantly lower than the value obtained from A.S. (P < 0.01 by Student’s t-test). Similar results were obtained from a smaller number of observations on apo B levels before and after apheresis. The mean reduction in apo B level was 72.5% f 3% in A.S. (4 observations) and 61.9 f 3% in the FH patients (20 observations). Again, the difference between the two means was significant (P < 0.01 by Student’s t-test).
0
ESc
-20
z c =
-40
.E
! .[J
1;
252 -100
r
I
I
0
3
7 Days
I
14
after apheresis
Fig. 2. Percentage reduction in serum LDL-cholesterol (LDLC) concentration and return to baseline value over a 14day period after LDL apheresis in a patient (AS.) with heterozygous familial defective apolipoprotein B-100 @) and in five patients with hcterozygous familial hypercholesterolaemia (0). In each procedure a volume of plasma equal to the patient’s total plasma volume, calculated from the patient’s body weight, was filtered.
234
The serum LDL-C level was measured at 3, 7 and 14 days after apheresis on a single occasion in A.S. and in each of the 5 FH patients. The rate of return of the serum LDL-C level to the baseline value was similar in all 6 patients (Fig. 2). After LDL apheresis for 1 year, AS’s angina disappeared and his exercise test performance improved, the time to 1 mm ST segment depression on a Bruce protocol increasing from 6 to 9 min.
Acknowledgement We are grateful to Dr. Iris Trayner for the apo B measurements. J.J.G. and N.B.M. were supported by the British Heart Foundation. References 1
Discussion 2
Our observations on this patient raise two points of interest in relation to FDB. First, we have made use of a unique opportunity to study retrospectively the response of a patient with FDB to long-term lipid-lowering treatment carried out over a total of more than 8 years. The improvement in exercise test performance and the remission of the patient’s angina after plasma exchange or LDL apheresis (both combined with drug treatment) suggest that FDB patients with coronary disease are likely to benefit clinically from prolonged lowering of their serum lipids levels, whether by drugs or by extracorporeal removal of lipid. Second, the extent of the fall in serum LDL level after LDL apheresis shows that the FDB patient’s LDL was adsorbed by the columns at least as efficiently as the LDL of FH patients, strongly suggesting that the loss of a basic residue at position 3500 in apo B-100 does not diminish its affinity for dextran sulphate. Indeed, the greater reduction in serum LDL-C and apo B levels in A.S. than in the FH patients raises the possibility that lipoproteins containing the mutant species of apo B-100 are removed by dextran sulphate columns more efficiently than are lipoproteins with normal apo B. Observations on additional FDB patients would, of course, be needed to establish whether or not this is so. It should be noted that our findings on the effectiveness of dextran sulphate columns in removing LDL from an FDB patient are not necessarily applicable to columns in which the adsorbant is an antibody to LDL. In conclusion, our findings on A.S. suggest that LDL apheresis is an appropriate form of treatment for FDB patients who require greater reduction of their serum lipid levels than-is achievable by drugs alone.
3
4
6
Soria, L.F., Ludwig, E.H., Clarke, H.R.G., Vega, G.L., Grundy, SM. and McCarthy, B.J., Association between a specific apolipoprotein B mutation and familial defective apolipoprotein B-100, Proc. NatI. Acad. Sci. USA, 86 (1988) 587. Innerarity, T.L., Mahley, R.W., Weisgraber, K.H. et al., Familial defective apolipoprotein B-1001 A mutation of apolipoprotein B that causes hypercholesterolemia, J. Lipid Res., 31 (1990) 1337. Innerarity, T.L., Weisgraber, K.H., Arnold, K.S. et al., Familial defective apolipoprotein B-100: Low density lipoprotein with abnormal receptor binding, Proc. Natl. Acad. Sci. USA, 84 (1987) 6919. Tybjaerg-Hansen, A., Gallagher, J., Vincent, J. et al., Familial defective apolipoprotein B-100: detection in the United Kingdom and Scandinavia and clinical characteristics of 10 cases, Atherosclerosis, 80 (1990) 235. Schuster, H., Rauh, G., Kormann, B. et al., Familial defective apolipoprotein B-100. Comparison with familial hypercholesterolemia in 18 cases detected in Munich, Arteriosclerosis, 10 (1990) 577. Maher, V.M.G., Gallagher, J.J., Perombelon, N., Thompson, G.R. and Myant, N.B., Coronary heart disease in familial defective apolipoprotein B-100, Eur. Heart J., 12 (1991) 1407. Myant, N.B., Gallagher, J.J., Knight, B.L. et al., Clinical signs of familial hypcrcholesterolemia in patients with familial defective apolipoprotein B-108 and normal lowdensity lipoprotein receptor function, Arterioscler. Thromb., 11 (1991) 691. Maher, V.M.G., Gallagher, J., Thompson, G.R. and Myant, N.B., Response to cholesterol-lowering drugs in familial defective apolipoprotein B-100, Atherosclerosis, 91 (1991) 73. Thompson, G.R., Lowenthai, R. and Myant, N.B., Plasma exchange in the management of homozygous familial hypercholesterolaemia, Lancet, 1 (1975) 1208. Thompson, G.R., Miller, J.P. and Breslow, J.L., Improved survival of patients with homozygous familial hypercholesterolaemia treated with plasma exchange, Br. Med. J., 291 (1985) 1671. Mabuchi, H., Michishita, I., Takeda, M., Fujita, H., Koizumi, J., Takeda, M., Takada, S. and Michikazu, O., A new low-density lipoprotein apheresis system using dextran sulphate cellulose columns in an automated column unit (LDL continuous aphereis), regenerating Atherosclerosis, 68 (1987) 19. Borberg, H., Gaczkowski, A., Hombach, V., Oette, K. and Stoffel, W., Treatment of familial hypercholesterolaemia by means of specific immunoadsorption, J. Clin. Apheresis, 4 (1988)‘59.
231
Atherosclerosis,
ATHERO 04874
Effective reduction of plasma LDL levels by LDL apheresis in familial defective apolipoprotein B- 100 Vincent M.G. Mahera’b, Yuri Kitanoa, Claire Neuwirtha, John J. Gallagher”, Gilbert R. Thompsona and Nicholas B. Myant” ‘MRC
Lipoprotein
Team and hDepartment
of Cardiology,
Hammersmith
Hospital,
DuCane
Road, London
WI2 OHS (UK)
(Received 13 March, 1992) (Revised, received 1 June, 1992) (Accepted 3 June, 1992)
Summary
The clinical response to long-term reduction of the plasma LDL cholesterol concentration was studied in a man with severe coronary artery disease associated with familial defective apolipoprotein B-100 (FDB). Plasma exchange repeated at 2-week intervals, combined with lipid-lowering drugs, led to remission of angina and improved exercise test performance. A similar clinical response was achieved after LDL apheresis with dextran sulphate columns repeated once every 2 weeks in combination with drug treatment. The reduction in plasma LDL cholesterol level brought about by LDL apheresis was at least as marked in the FDB patient as in 5 patients with familial hypercholesterolaemia. We conclude that FDB patients with coronary artery disease may derive clinical benefit from prolonged reduction of their plasma cholesterol levels and that LDL containing apo B-100 in which arginine at position 3500 is replaced by glutamine is removed from plasma by dextran sulphate columns as efficiently as is normal LDL.
Key words: Familial defective apolipoprotein
B-100; LDL apheresis
Introduction
Apolipoprotein B-100 (apo B-100) is the protein component of low-density lipoprotein (LDL) and is responsible for the recognition of LDL by LDL receptors. Familial defective apo B-100 (FDB) is a Corres,mw+ence to: Dr. Vincent Maher, MRC Lipoprotein Team, Hammersmith Hospital, DuCane Road, London WI2 OHS, UK. Tel.! 081-7403262; Fax: 081-7460586.
dominantly inherited abnormality of apo B-100 in which arginine at residue 3500 is replaced by glutamine [l]. This amino acid substitution decreases the binding of LDL by the LDL receptor by more than 95%, leading to hypercholesterolaemia in most FDB heterozygotes [2]. Since each LDL particle contains only one molecule of apo B100, the serum of an FDB heterozygote contains two populations of LDL particles, one with apo B encoded in the normal gene and the other with the
232
apo B variant. The hypercholesterolaemia in FDB heterozygotes is due to accumulation of defective LDL particles containing the mutant apo B-100 [31. Since many patients with FDB develop premature coronary heart disease (CHD) [4-71, it is essential to treat the hypercholesterolaemia that usually occurs in this condition. We have shown that drugs that lower the serum cholesterol level by stimulating LDL receptor activity are as effective in FDB as in familial hypercholesterolaemia (FH) [8]. However, in some patients with critically severe coronary artery disease it may be desirable to achieve very marked reductions of the plasma cholesterol level using additional methods, in order to arrest or reverse coronary atherosclerosis. In the treatment of FH, extracorporeal removal of plasma cholesterol by repeated plasma exchange has been shown to bring about a marked reduction in the serum cholesterol level [9] and to prolong life [lo]. As a means of reducing the serum cholesterol level, plasma exchange has been superseded by LDL apheresis, a procedure in which LDL and other apo B-containing lipoproteins are removed extracorporeally by selective adsorption on columns of dextran sulphate [ 1l] or
other adsorptive agents. In patients with FH (in which apo B is normal), LDL apheresis lowers the serum cholesterol level and may induce regression of coronary atherosclerosis [12], but its use in the treatment of FDB has not been reported previously. However, provided that the mutation in apo B does not affect the binding of LDL by the columns, this procedure should be as effective in FDB as in FH. In this communication we describe the response of a patient with FDB to repeated LDL apheresis. Our observations indicate that dextran-sulphate columns remove defective and normal LDL from the circulation with similar efficiency. Methods Serum lipids and lipoprotein concentrations were determined as described [7]. Serum apo B concentration was measured by an immunonephelometric method with the Beckman Immunochemistry System Analyser (ICS) (Beckman Instruments Limited, High Wycombe, UK). FDB was diagnosed by amplifying the relevant segment of the patient’s apo B gene, followed by hybridization with radioactive oligonucleotide probes [4].
I
LW cholsstemlmodid fat diet Diet 16&l Cholestyramins LlsOl 249
I
2a
Nkotinic add
4omn
Lwmtatin Simvastatin
I
8oma
1
4omp
I
mw
Plasmaexbange LDL aphemis
10 a-
a-
0 r
a2
’ a3
1 a4
’ a5
’ aa ’ a7 ’ 88 ’ a9 ’ 90
’ 91
’ 92
’
Year
Fig. 1. SerumLDL cholesterol (LDL-C) concentration in a patient (A.S.) with familial defective apolipoprotein B-100 during treatment with cholesterol-lowering drugs, plasma exchange and LDL apheresis over a 9-year period (1983-1992).
233
LDL-receptor function in the patient’s ftbroblasts in culture was assayed as described (71. Plasma exchange [9] and LDL apheresis [1 1] were carried out by methods previously described.
Clinical background The patient is a 59-year-old man. At the age of
49 he was found to have marked hyperlipidaemia (serum cholesterol 13 mmoY1; triglycerides 4.4 mmol/l), angina of effort and extensive xanthomas on the tendons of his left hand. He also had a family history of premature CHD. Initially he was given a clinical diagnosis of heterozygous FH but was later shown to have FDB with normal LDL receptor function (AS. in Table 1 of Ref. 7). His serum LDL cholesterol (LDL-C) level responded well to a low-cholesterol modified fat diet, cholestyramine and nicotinic acid (Fig. 1), although his angina persisted. An exercise test at age 52 showed 1 mm ST segment depression after 6 min on a modified Bruce protocol; coronary angiography revealed totally occluded circumflex and right coronary arteries, both of which filled retrogradely from the left anterior descending artery which had a 40% stenosis distal to the first diagonal branch. The patient who was unsuitable for coronary angioplasty was offered, but refused, coronary artery bypass surgery. In view of the severity of his coronary artery disease and of his clinical condition, it was thought essential to achieve an even greater reduction of his serum LDL level than the 50% reduction already achieved by drugs. He was therefore treated by plasma exchange once every 2 weeks, combined with cholestyramine and lovastatin (Fig. 1). While on this treatment his integrated mean serum LDL-C level between procedures fell to less than 3 mmohl. This led to the disappearance of his angina after 6 months and to improved exercise test performances. Plasma exchange was discontinued after 18 months and his drug treatment was adjusted (Fig. 1). He remained well for about 3 years after which his angina returned, though in less severe form than that prior to plasma exchange. His exercise test performance had also deteriorated during this period. His symptoms were controlled with glyceryl trinitrate. However, because the recurrence of his angina suggested progression of coronary artery disease it was
decided to supplement LDL apheresis.
his drug treatment
with
Response to LDL apheresis
LDL apheresis with twin dextran sulphate columns, performed once every 2 weeks, was begun in July 1990 and has continued until the present time. In order to determine the maximum effect of a single procedure on A.S.‘s serum LDL-C level, the levels were measured before and immediately after apheresis in a total of 10 procedures during the course of his treatment. The mean reduction in LDL-C level in the 10 procedures was 77.6% f 2%. Similar measurements were made on 5 FH heterozygotes with CHD who were concurrently undergoing LDL apheresis (3 males and 2 females, mean age 47 years). In a total of 57 procedures the mean value (64.1% f 6%) was significantly lower than the value obtained from A.S. (P < 0.01 by Student’s t-test). Similar results were obtained from a smaller number of observations on apo B levels before and after apheresis. The mean reduction in apo B level was 72.5% f 3% in A.S. (4 observations) and 61.9 f 3% in the FH patients (20 observations). Again, the difference between the two means was significant (P < 0.01 by Student’s t-test).
0
ESc
-20
z c =
-40
.E
! .[J
1;
252 -100
r
I
I
0
3
7 Days
I
14
after apheresis
Fig. 2. Percentage reduction in serum LDL-cholesterol (LDLC) concentration and return to baseline value over a 14day period after LDL apheresis in a patient (AS.) with heterozygous familial defective apolipoprotein B-100 @) and in five patients with hcterozygous familial hypercholesterolaemia (0). In each procedure a volume of plasma equal to the patient’s total plasma volume, calculated from the patient’s body weight, was filtered.
234
The serum LDL-C level was measured at 3, 7 and 14 days after apheresis on a single occasion in A.S. and in each of the 5 FH patients. The rate of return of the serum LDL-C level to the baseline value was similar in all 6 patients (Fig. 2). After LDL apheresis for 1 year, AS’s angina disappeared and his exercise test performance improved, the time to 1 mm ST segment depression on a Bruce protocol increasing from 6 to 9 min.
Acknowledgement We are grateful to Dr. Iris Trayner for the apo B measurements. J.J.G. and N.B.M. were supported by the British Heart Foundation. References 1
Discussion 2
Our observations on this patient raise two points of interest in relation to FDB. First, we have made use of a unique opportunity to study retrospectively the response of a patient with FDB to long-term lipid-lowering treatment carried out over a total of more than 8 years. The improvement in exercise test performance and the remission of the patient’s angina after plasma exchange or LDL apheresis (both combined with drug treatment) suggest that FDB patients with coronary disease are likely to benefit clinically from prolonged lowering of their serum lipids levels, whether by drugs or by extracorporeal removal of lipid. Second, the extent of the fall in serum LDL level after LDL apheresis shows that the FDB patient’s LDL was adsorbed by the columns at least as efficiently as the LDL of FH patients, strongly suggesting that the loss of a basic residue at position 3500 in apo B-100 does not diminish its affinity for dextran sulphate. Indeed, the greater reduction in serum LDL-C and apo B levels in A.S. than in the FH patients raises the possibility that lipoproteins containing the mutant species of apo B-100 are removed by dextran sulphate columns more efficiently than are lipoproteins with normal apo B. Observations on additional FDB patients would, of course, be needed to establish whether or not this is so. It should be noted that our findings on the effectiveness of dextran sulphate columns in removing LDL from an FDB patient are not necessarily applicable to columns in which the adsorbant is an antibody to LDL. In conclusion, our findings on A.S. suggest that LDL apheresis is an appropriate form of treatment for FDB patients who require greater reduction of their serum lipid levels than-is achievable by drugs alone.
3
4
6
Soria, L.F., Ludwig, E.H., Clarke, H.R.G., Vega, G.L., Grundy, SM. and McCarthy, B.J., Association between a specific apolipoprotein B mutation and familial defective apolipoprotein B-100, Proc. NatI. Acad. Sci. USA, 86 (1988) 587. Innerarity, T.L., Mahley, R.W., Weisgraber, K.H. et al., Familial defective apolipoprotein B-1001 A mutation of apolipoprotein B that causes hypercholesterolemia, J. Lipid Res., 31 (1990) 1337. Innerarity, T.L., Weisgraber, K.H., Arnold, K.S. et al., Familial defective apolipoprotein B-100: Low density lipoprotein with abnormal receptor binding, Proc. Natl. Acad. Sci. USA, 84 (1987) 6919. Tybjaerg-Hansen, A., Gallagher, J., Vincent, J. et al., Familial defective apolipoprotein B-100: detection in the United Kingdom and Scandinavia and clinical characteristics of 10 cases, Atherosclerosis, 80 (1990) 235. Schuster, H., Rauh, G., Kormann, B. et al., Familial defective apolipoprotein B-100. Comparison with familial hypercholesterolemia in 18 cases detected in Munich, Arteriosclerosis, 10 (1990) 577. Maher, V.M.G., Gallagher, J.J., Perombelon, N., Thompson, G.R. and Myant, N.B., Coronary heart disease in familial defective apolipoprotein B-100, Eur. Heart J., 12 (1991) 1407. Myant, N.B., Gallagher, J.J., Knight, B.L. et al., Clinical signs of familial hypcrcholesterolemia in patients with familial defective apolipoprotein B-108 and normal lowdensity lipoprotein receptor function, Arterioscler. Thromb., 11 (1991) 691. Maher, V.M.G., Gallagher, J., Thompson, G.R. and Myant, N.B., Response to cholesterol-lowering drugs in familial defective apolipoprotein B-100, Atherosclerosis, 91 (1991) 73. Thompson, G.R., Lowenthai, R. and Myant, N.B., Plasma exchange in the management of homozygous familial hypercholesterolaemia, Lancet, 1 (1975) 1208. Thompson, G.R., Miller, J.P. and Breslow, J.L., Improved survival of patients with homozygous familial hypercholesterolaemia treated with plasma exchange, Br. Med. J., 291 (1985) 1671. Mabuchi, H., Michishita, I., Takeda, M., Fujita, H., Koizumi, J., Takeda, M., Takada, S. and Michikazu, O., A new low-density lipoprotein apheresis system using dextran sulphate cellulose columns in an automated column unit (LDL continuous aphereis), regenerating Atherosclerosis, 68 (1987) 19. Borberg, H., Gaczkowski, A., Hombach, V., Oette, K. and Stoffel, W., Treatment of familial hypercholesterolaemia by means of specific immunoadsorption, J. Clin. Apheresis, 4 (1988)‘59.
