This is the published version of a paper published in Orphanet Journal of Rare Diseases.
Citation for the original published paper (version of record):
Chien, Y., Abdenur, J., Baronio, F., Bannick, A., Corrales, F. et al. (2015)
Mudd's disease (MAT I/III deficiency): a survey of data for MAT1A homozygotes and compound heterozygotes.
Orphanet Journal of Rare Diseases, 10
http://dx.doi.org/10.1186/s13023-015-0321-y
Access to the published version may require subscription.
N.B. When citing this work, cite the original published paper.
Permanent link to this version:
http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-108133
R E S E A R C H Open Access
Mudd ’s disease (MAT I/III deficiency):
a survey of data for MAT1A homozygotes and compound heterozygotes
Yin-Hsiu Chien 1 , Jose E. Abdenur 2 , Federico Baronio 3 , Allison Anne Bannick 4 , Fernando Corrales 5 , Maria Couce 6 , Markus G. Donner 7 , Can Ficicioglu 8 , Cynthia Freehauf 9 , Deborah Frithiof 10 , Garrett Gotway 11 , Koichi Hirabayashi 12 , Floris Hofstede 13 , George Hoganson 14 , Wuh-Liang Hwu 1 , Philip James 15 , Sook Kim 16 , Stanley H. Korman 17 , Robin Lachmann 18 , Harvey Levy 15 , Martin Lindner 19,20 , Lilia Lykopoulou 21 , Ertan Mayatepek 22 , Ania Muntau 23 , Yoshiyuki Okano 24 , Kimiyo Raymond 25 , Estela Rubio-Gozalbo 26 , Sabine Scholl-Bürgi 27 , Andreas Schulze 28 , Rani Singh 29 , Sally Stabler 30 , Mary Stuy 31 , Janet Thomas 9 , Conrad Wagner 32 , William G. Wilson 33 ,
Saskia Wortmann 34 , Shigenori Yamamoto 35 , Maryland Pao 36 and Henk J. Blom 37*
Abstract
Background: This paper summarizes the results of a group effort to bring together the worldwide available data on patients who are either homozygotes or compound heterozygotes for mutations in MAT1A. MAT1A encodes the subunit that forms two methionine adenosyltransferase isoenzymes, tetrameric MAT I and dimeric MAT III, that catalyze the conversion of methionine and ATP to S-adenosylmethionine (AdoMet). Subnormal MAT I/III activity leads to hypermethioninemia. Individuals, with hypermethioninemia due to one of the MAT1A mutations that in heterozygotes cause relatively mild and clinically benign hypermethioninemia are currently often being flagged in screening programs measuring methionine elevation to identify newborns with defective cystathionine β-synthase activity. Homozygotes or compound heterozygotes for MAT1A mutations are less frequent. Some but not all, such individuals have manifested demyelination or other CNS abnormalities.
Purpose of the study: The goals of the present effort have been to determine the frequency of such abnormalities, to find how best to predict whether they will occur, and to evaluate the outcomes of the variety of treatment regimens that have been used. Data have been gathered for 64 patients, of whom 32 have some evidence of CNS abnormalities (based mainly on MRI findings), and 32 do not have such evidence.
Results and Discussion: The results show that mean plasma methionine concentrations provide the best indication of the group into which a given patient will fall: those with means of 800 μM or higher usually have evidence of CNS abnormalities, whereas those with lower means usually do not. Data are reported for individual patients for MAT1A genotypes, plasma methionine, total homocysteine (tHcy), and AdoMet concentrations, liver function studies, results of 15 pregnancies, and the outcomes of dietary methionine restriction and/or AdoMet supplementation. Possible pathophysiological mechanisms that might contribute to CNS damage are discussed, and tentative suggestions are put forth as to optimal management.
* Correspondence: henk.blom@uniklinik-freiburg.de
37
Laboratory for Clinical Biochemistry and Metabolism, Center for Pediatrics and Adolescent Medicine University Hospital Freiburg, 79106 Freiburg, Germany
Full list of author information is available at the end of the article
© 2015 Chien et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Background
More than sixty years ago Giulio Cantoni described an enzyme that utilized methionine and ATP to form a then novel product needed for transmethylation reac- tions [1], which he soon identified as S-adenosyl- methionine (AdoMet) [2]. Since then, AdoMet has turned out to be among the most versatile compounds in all of biology. In humans AdoMet is used by as many as 200 or more methyltransferases [3]; after decarboxyl- ation, as a source of aminopropyl groups in polyamine biosynthesis [4]; possibly as a source of other moieties [5]; and as a regulator of sulfur amino acid metabolism [6] and liver function [7]. Evidence has been presented that humans have a few enzymes that, as members of the group of more than 2800 proteins that comprise the biologically widespread radical SAM superfamily, use a 5′-deoxyadenosyl radical derived from AdoMet [8]. The structure of methionine adenosyltransferase (MAT)(E.C. 2.5.1.6), the enzyme that synthesizes AdoMet has been highly conserved during evolution: in a study of 292 MAT genes occurring in bacteria and eukaryota there was perfect conservation of active site residues, approxi- mately 30 % of the encoded amino acids were identical in all species [9]. Humans possess two genes encoding iso- forms of MAT: MAT1A encodes a catalytic subunit that forms the tetrameric and dimeric holoenzymes, MAT I and MAT III. MAT2A encodes the catalytic subunit of MAT II [10]. Sánchez-Pérez et al. found that each ver- tebrate included in their study had two MAT genes that encoded amino acid sequences with about 85 % iden- tity, suggesting a gene duplication that occurred after the human lineage diverged from the sea squirts (Uro- chordata), but before divergence from the jawed verte- brates (Teleostomi) [9], perhaps 400–500 million years ago. MAT II is the major isozyme in non-hepatic tis- sues and in fetal liver, whereas MAT I and III are the major forms present in post-natal liver [10]. However, MAT1A expression has been reported in pancreas [11]
and, more recently, in small amounts in most tissues, including brain [12]. After the introduction of screening newborns for methionine elevations to detect homocys- tinuria due to cystathionine β-synthase deficiency, in- fants were discovered in the United States [13], France [14], and Japan [15] with elevated blood methionine but without abnormal levels of homocystine, and MAT ac- tivities were shown to be low in extracts of their livers [13, 15–18], as well as in that of an adult patient found to be hypermethioninemic when investigated because of malodorous breath due to dimethylsulfide [19, 20].
The kinetic properties of the residual hepatic MAT ac- tivities of these patients [16, 19] as well as the finding that MAT activities in a variety of their non-hepatic tis- sues were normal indicted that the defective activity was that encoded by MAT1A [16, 17, 21]. Establishment of the
amino acid sequence encoded by MAT1A [22–24] then opened the way to finding MAT1A mutations in most of the patients in question [25–27]. As screening of new- borns for methionine elevations has expanded, MAT1A mutations are turning out to be the most common genetic cause of newborn hypermethioninemia [28–31]. Most such cases are heterozygous for R264H, a mutation in which the activity of wild-type subunits is suppressed by combination with mutant subunits [32, 33]. Several other such dominant mutations have now been identi- fied [31, 34, 35]. Clinically, heterozygotes for such mu- tations have been unaffected. However, in addition, a number of patients with homozygous or compound het- erozygous MAT1A mutations have been found through newborn screening [30, 31, 36–44], and although some of these patients have been clinically unaffected, some of them have had brain demyelination or other MRI abnor- malities. Treatments used have included dietary methio- nine restriction or supplementation with AdoMet, but optimal management has not yet been clearly established.
With the aim of providing information on the criteria for prognosis and optimal treatment of such patients we have recently made an effort to collect as much information as possible on the clinical status and outcomes and the meta- bolic details of patients for whom sequencing has shown either homozygous or compound heterozygous MAT1A mutations, or those with hypermethioninemia and defi- cient MAT activities. The findings are presented and dis- cussed in this paper.
Methods
A literature search was carried out to identify patients who had been found to be homozygotes or compound heterozygotes for MAT1A mutations or who, although not genotyped, had been shown to have deficient activ- ities of hepatic MAT. Information on such patients was taken from relevant publications and analyzed together, whenever possible, with updated information submitted by coauthors based on their experiences in manage- ment of, or diagnostic studies of, the patients in ques- tion. In addition, physicians taking care of MAT I/III patients came known to the authors via support in the diagnostic process or counseling on potential treatment of these patients. Informed consent was obtained from the patients or their parents and local ethical rules were followed. Ethical approval was obtained from the Office of Human Subjects Research (OHSR) at the NIH, Bethesda, USA.
Patients were considered to have “CNS abnormality” if their brain MRI showed abnormalities or if presence of any neurological symptom was reported or both.
In Tables 1 and 2 the references are given of those pa-
tients that have been published before.
Table 1 Patients without evidence of CNS abnormalities Patient Sex Age at last
report years
MAT1A allele 1/allele 2
MAT activity
% of WT
Cause ascer- tain Met
Age < 5 m Met range
Age ≥ 5 m Met mean ± SD
MRI (age) Citation
†G1 F 40.4 c.966T>G (p.Ile322Met) 7.8* NBS 1270 373 ± 133 Normal (22) [17, 25, 46, 58]
c.966T>G (p.Ile322Met) 21/21
G2 M 38 c.914T>C (p.Leu305Pro) 10.2* NBS 364 –583 394 ± 118 — [17, 25]
c.966T>G (p.Ile322Met) 26/21
G3 F 2 c.164C>A (p.Arg55Asp) 10.91* NBS 389 –1020 315 — [17, 25]
c.1070C>T (p.Pro357Leu) 26/31
G4 F 31.4 c.1068G>A (p.Arg356Gln) 17.5* NBS 42 –408 146 ± 38 — [17, 26]
c.1132G>A (p.Gly378Ser) 11/0.2 402
2 M 60.1 c.539insTG (p.Thr185X) 28* Breath odor — 805 ± 106 Normal (31) [19, 20, 78]
c.539insTG (p.Thr185X)
3 F 21.5 c.539insTG (p.Thr185X) NA NBS 1870 –2542 777 ± 169 Normal (6) [26, 58]
c.539insTG (p.Thr185X) 1870
10
aM 25 c.595C>T (p.Arg199Cys) 11/11 NBS 496 –670 520 ± 124 — [26, 58]
c.595C>T (p.Arg199Cys) 670
11
aF 28.5 c.595C>T (p.Arg199Cys) 11/11 NBS 591 –654 475 ± 118 — [26, 58]
c.595C>T (p.Arg199Cys) 591
14 F 6.4 c.966T>G (p.Ile322Met) 11/11 NBS 440 –467 225 ± 57 — [27, 58]
c.1031A>C (p.Glu344Ala)
15
bF 2.2 c.1132G>A (p.Gly378Ser) 0.2/75 NBS 383 –1089 519 — [80]
c.1161G>A (p.Trp387X)
16
bF 4.7 c.1132G>A (p.Gly378Ser) 0.2/75 Family — 782 ± 400 — [80]
c.1161G>A (p.Trp387X)
17 F 21.4 c.791C>T (p.Arg264Cys) 0.3/31 NBS 648 322 — [42]
c.1070C>T (p.Pro357Leu)
18 M 21.2 c.1070C>T (p.Pro357Leu) 31/31 NBS 505 325 ± 244 — [42]
c.1070C>T (p.Pro357Leu)
19 F 16.5 c.1067G>C (p.Arg356Pro) 11/31 NBS 622 175 — [34, 42]
c.1070C>T (p.Pro357Leu)
21 F 7.1 c.836G>T (p.Gly279Val) NA/2 NBS 596 436 ± 1 — [34]
c.964A>G (p.Ile322Val)
23 F 3.9 c.539insTG (p.Thr185X) NA NBS 216 –1457 665 ± 160 — [38]
c.822G>C (p.Trp274Ser)
24
cM 1.2 c.689T>G (p.Val230Gly) NA NBS 518 –525 769 ± 112 —
c.689T>G (p.Val230Gly)
25
cF 4.9 c.689T>G (p.Val230Gly) NA Family – 838 ± 18 —
c.689T>G (p.Val230Gly)
26 F 2.9 c.527T>A (p.Leu176Gln) NA NBS
57
57 –200 76 ± 24 —
c.527T>A (p.Leu176Gln)
28 F 20 c.65C>T (p.Ser22Leu) 46/46 NBS — 975 ± 177 normal (20) [34, 37, 44]
c.65C>T (p.Ser22Leu)
33 U 2 c.856G>A (p.Asp286Asn) NA NBS 106 –1570
del at least exons 6-8
40 F 0.4 c.1141G>A (p.Gly381Arg) 25/25 NBS 1207 –2121 1673 — [34]
Results Summary tables
Currently data are available for 64 patients. Because a sub- stantial portion of these patients have evidence of CNS ab- normalities, we divided them between those without (Table 1) (n = 32) and with evidence of CNS abnormalities (Table 2) (n = 32). These Tables show many more import- ant features of the patients, including their MAT1A geno- types, their age at last report, cause of ascertainment, plasma methionine concentrations and whether MRI’s, if performed, were normal or abnormal. Tables 3 and 4 present the brief clinical histories of the patients with pos- sible CNS abnormalities, the interventions used (if any), and the MRI findings at specified ages.
Possible criteria to distinguish between those with and without CNS problem (Tables 1 and 2)
MAT1A genotypes
MAT1A genotypes are not clearly predictive. Patients with homozygous truncating mutations with presumably
no residual MAT I/III activity are found among those without CNS problems (patients 2 and 3), and most of the patients with CNS problems have only missense mu- tations which, when expressed in E. coli, had some re- sidual MAT activities.
Plasma methionine concentrations
For untreated patients for whom more than one value for plasma methionine during the first few months of life were available, values often varied relatively widely (Fig. 1). After that time methionine concentrations tended to be less variable for a given patient. As shown in Fig. 2, on normal diets mean methionine values for patients with evidence of CNS abnormalities were usu- ally higher than were those for patients without evidence of such abnormalities. Those with mean values above 800 μM almost always have CNS abnormalities, whereas those with means less than 800 μM usually do not. In the total group (all ages) three patients with CNS abnor- malities were below 800 μM and six patients without Table 1 Patients without evidence of CNS abnormalities (Continued)
c.1141G>A (p.Gly381Arg)
44 M 0.2 c.529C>T (p.Arg177Trp) NA NBS
97
97 –641 — —
c.529C>T (p.Arg177Trp)
48 M 5.4 c.446T>A (p.Met64Lys) NA NBS
134
134 –1567 — Normal (yearly,
final at 5) DQ 88 [39]
c.589delC (p.Pro197Leufs*26)
49 F 0.3 c.110T>C (p.Ile37Thr) NA NBS
407
403 –408 — — [31]
c.271G>A (p.Gly91Ser)
52 M 0.54 c.823G>C (p.Gly275Arg) NA NBS 949 –1074 — normal (0.5)
c.823G>C (p.Gly275Arg)
53 F 2.3 c.862A>G (p.Thr288Ala) NA NBS 121 –484 495 ± 275 [30]
c.862A>G (p.Thr288Ala)
54 F 2.0 c.1064T>G (p.Leu355Arg) NA NBS
185
185 –410 — — [30]
c.1064T>G (p.Leu355Arg)
57 U 3.5 c.169+1G>A NA NBS
860
860 –1130 918 ± 84 —
c.169+1G>A
58
dM 12.3 not sequenced 22.7* NBS 268 –1005 369 ± 237 — [15]
268
59
dM 13.7 not sequenced 23.1* Family — 350 ± 50 — [15]
64 M 4.5 m c.596G>A (p.Arg199His) NA NBS 118 –208 — —
c.596G>A (p.Arg199His)
†
Patients are assigned the same identifiers as were used when they were first described in the following papers: Patients G1, G2, G3, G4 [17]; Patients 3, 10, 11 [58]; Patients 17, 18, 19; numbers 1, 2 and 5 [42]; Patient 28: patient 1 [44]; Patients 53, 54: patients 14 and 18 [30]
*Activity based on assay of hepatic extract; others based on activity of mutant recombinant forms expressed in E coli [ 34]
a
Sibs are designated by the same superscript
†
Cont. indicates that methionine restriction or AdoMet supplementation was continuing at last report NBS: Newborn screening
NA: not available
Met: methionine concentration in umol/L
CNS abnormalies were above 800 μM. The respective means (± SD) for these two groups were 1073 μM ± 233 and 485 μM ± 276.
Plasma AdoMet concentrations
Data for the available concentrations of plasma AdoMet at age ≥ 5 months are shown in Fig. 3. Although, as already shown in Fig. 2, most patients with evidence of CNS abnormalities have higher plasma methionines, there is no trend for a difference in the AdoMet con- centrations between those with and without such evi- dence, and the mean values (± SD) were, respectively 84 nM ± 19 and 72 nM ± 13.
Plasma total homocysteine (tHcy) values
Figure 4 shows values of plasma methionine and tHcy for the individual samples in which both of these were assayed. To provide more indication of the range of values encountered at young ages, points are plotted for samples drawn either before (circles) or after (triangles) age 5 months. As plasma methionine rises, tHcy tends to rise also, so that patients with evidence of CNS abnormal- ities tend to have higher levels of tHcy. However at the higher methionine concentrations there is no apparent difference in the tHcy values between those with and without CNS abnormalities, indicating the response to methionine elevation is about the same in the two groups.
Plasma cystathionine values
Among the few patients for whom sensitive serial assays of cystathionine were performed at early ages cystathio- nines were mildly elevated at 16 days, 21 days, 38 days and 1.5 months with values, respectively of 776, 1196, 1280, and 1001 nM (adult reference range 44–342 nM).
Values had fallen to 566 and 670 nM by 11 months and thereafter were, at most, only slightly above the refer- ence range (data not shown in Tables).
Liver function studies
The results of liver function studies are available for 16/32 patients without and 14/32 of those with evi- dence of CNS abnormalities. Included are assays (in some patient multiple times) of ALT and AST, total bili- rubin, alkaline phosphatase, albumin, total plasma pro- tein, and gamma glutamyltranspeptidase. No instances of hepatic malfunction have been detected by these studies (data not shown in Tables).
Pregnancy outcomes
Information is available on 15 pregnancies among six of the present patients:
Patient G1 had four pregnancies. Because the patient’s plasma choline was below the reference range, and
because brain damage occurs in fetuses of experimental animal mothers fed low choline diets [45], she was advised after gestation week 17 in three of these pregnancies to ingest two eggs daily to provide about 630 mg choline/day. Three normal children were born who have continued to develop normally mentally and physically. In the fourth pregnancy there were no overt complications but sonography at ten weeks disclosed fetal arrest and the pregnancy was terminated two weeks later [46].
Patient G4 took 600 mg choline/day during most of her initial pregnancy and produced a normal baby. During a second pregnancy she took 2 eggs/day from 18 weeks gestation, and then changed to choline capsules, 600 mg/d during the remainder of the pregnancy. A normal child was born who continued to be normal at last investigation at age 6 months.
Patient 3 had been temporarily lost to follow-up, but was relocated and found to have produced a normal baby without any specific treatment due to her MAT I/III deficiency.
Patient 5 had also been lost to follow-up after childhood, but was found again when she produced a baby that was flagged during NBS for elevated methionine that turned out to be transient [47].
Patient 4 produced a normal baby after a pregnancy during which she continued her usual dose of AdoMet, 200 mg bid.
Patient 56 was ascertained at age 38 with elevated methionine and tHcy because she had given birth to two children with transient hypermethioninemia (NBS methionines of 552 and 554 μM, falling to 94 μM on day 5 or 42 μM on day 4 of life). Her history revealed that she had had six pregnancies with one lost at 4 weeks, a stillborn at 16 weeks, two blighted ovums and another 2 with transient hypermethioninemia.
Treatment outcomes Vitamin B6
Because of the mild elevations of tHcy often encoun-
tered in MAT1A deficient patients, 6 of the 32 with-
out and 7 of the 32 with evidence of CNS abnormalities
(data not shown in Tables) have been given brief tri-
als of high doses of vitamin B6. In almost all cases
there were no significant effects. One patient (#36)
did experience a marked decrease in plasma methio-
nine during an initial period of B6 treatment, but that
response did not occur during a second trial nor in
her identical twin sister (#37). In addition, even some
adverse events were reported in patients using high
doses of B6 [48]. One MAT I/III deficient infant (#7)
became apneic and required respiratory support shortly
after starting a dose of pyridoxine of 500 mg/day [49], and
Tada et al. reported that pyridoxine treatment may have
Table 2 Patients with evidence of CNS abnormalities Patient Sex Age last
report years
MAT1A allele 1/allele 2 MAT activity
% of WT
Cause ascer- tain-ment
Age < 5 m Met range
Age ≥ 5 m Met mean ± SD
MRI (age done) Other
Citation
†1 M 24.2 c.113G>A (p.Ser38Asp) 8* NBS 670 –1237 1030 Abnormal (20.7) [14, 16, 27, 58]
c.255delCA (p.Tyr92X) 0/NA 670
4 F 32 c.827insG (p.Lys351X) NA NBS — 600 –1400 Abnormal (11) [26, 64]
c.827insG (p.Lys351X) Normal (12)
5 F 26.1 c.791C>T (p.Arg264Cys) 0.3/23 NBS 201 –1740 909 ± 272 Normal (13) [27, 47, 58]
c.1006G>A (p.Gly336Arg) 201 IQ 84 (14)
Learning disability (14)
7 M 17.8 c.292G>A (splicing) NA NBS 1226 –1664 1428 ± 320 Normal (0.75) [27, 58]
c.292G>A (splicing) 1226 Abnormal (4.2)
Abnormal (11)
8 F 13.6 c.1043delTG (p.His350X) NA Dystonia — 1157 ± 445 Abnormal (9) [26, 58]
c.1043delTG (p.His350X)
9 M 8.7 c.595C>T (p.Arg199Cys) 11/NA NBS 966 –1467 879 ± 140 Normal (6) [26, 58]
c.539insTG (p.Thr185X) IQ 65 (6)
13 F 6.2 c.595C>T (p.Arg199Cys) 11/11 NBS 635 –738 485 ± 49 Abnormal (8) [26, 58]
c.595C>T (p.Arg199Cys) Slow at school (16)
20 F 10.8 c.205G>A (p.Gly69Ser) 109/NA NBS — 1400 Abnormal (10) [42]
c.1188G>T (p.X396YfsX464) 1560
22 F 7.5 c.874C>T (p.Arg292Cys) 14/NA NBS — 1005 –1676 Abnormal (2.9) [38, 81]
c.1067G>T (p.Arg356Leu) 395 Normal (6.4)
IQ 60 (5.4)
29 M 14.2 c.125T>C (p.Leu42Pro) 10/10 NBS 121 –1541 1437 ± 498 Abnormal (13) [34, 37, 44]
c.125T>C (p.Leu42Pro) 121 IQ 73 (13)
30
eM 7.0 c.274T>C (p.Tyr92His) 104/11 NBS 740 830 ± 368 IQ 121 (3) [34, 36, 41]
c.1067G>C (p.Arg356Pro) Abnormal (3.8)
Better (5.5) Normal (7)
31
eM 3 c.274T>C (p.Tyr92His) 104/11 NBS 820 –2250 900–1140 Abnormal (0.8) [34, 41]
c.1067G>C (p.Arg356Pro) Abnormal (3)
32 M 9.4 c.433G>A (p.Glu145Lys) NA/14 NBS 1740 –1870 740–1150 Abnormal (5) [34, 43]
c.874C>T (p.Arg292Cys) Abnormal (9.4)
IQ 108 (9.4)
34 M 0.63 c.1068G>A (p.Arg356Trp) 4/4 NA 1846 –3500 — Severe retarded [34]
c.1068G>A (p.Arg356Trp)
35 F 2.8 c.292G>A (splicing) NA/11 NBS 1544 –1685 1159 Abnormal (1.2) [26]
c.595C>T (p.Arg199Cys) Better (1.8)
36
fF 1.3 c.539insTG (p.Thr185X) NA/20 NBS † 1400 1549 Normal (2.3) [34]
c.890C>A (p.Ala297Asp) 1400 Delayed
development (2.3)
37
fF 1.3 c.539insTG (p.Thr185X) NA/20 NBS † 1400 1400 –1421 1614 Delayed
development (2.3) [34]
c.890C>A (p.Ala297Asp)
38
gF 13 c.896G>A (p.Arg299His) 13/13 Neuro-logical – 1016 ± 549 Abnormal (12.8) [34]
c.896G>A (p.Arg299His)
worsened the MRI and neurological abnormalities in their patient (#30) [36]. Taken together, high doses of vitamin B6 should not be used in patients with MAT I/III deficiency.
Dietary methionine restriction
Methionine restriction has been used for 8/32 patients without CNS abnormalities and 16/32 patients with CNS abnormalities, starting at various ages and continued for a Table 2 Patients with evidence of CNS abnormalities (Continued)
Delayed development (3)
39
gM 9.8 c.896G>A (p.Arg299His) 13/13 Family — 1000 ± 192 Abnormal (5.2) [34]
c.896G>A (p.Arg299His) Delayed in
learning (10.5)
41 F 7.6 p.MAT1Adel NA NBS 192 –1608 — Abnormal (0.2)
p.MAT1Adel 192 Normal (7.1)
42 M 1.9 c.607delATC (p.Ile203del) NA NBS 148 –1490 1144 ± 143 Abnormal (1.2)
c.607delATC (p.Ile203del) 148 Speech delay (1.5)
43 M 4.2 c.934C>T (p.Arg312Trp) NA NBS 460 –1437 1120 Abnormal (3.8)
c.934C>T (p.Arg312Trp) IQ 78 (3.3)
45 F 4.5 c.292G>C (p.Gly98Arg, splicing?)
NA NBS 507 –1012 901 ± 163 Abnormal (4)
c.292G>C (p.Gly98Arg, splicing?)
Better (4.5)
46 F 34 c.274T>C (p.Tyr92His) 8.3* NBS 402 –1340 1326 ± 159 Abnormal (30) [15]
c.1067G>C (p.Arg356Pro) 104/11 IQ 99 (9)
47 F 17 c.1033insG (p.Lys351X) NA Unknown — — Abnormal (9)
c.1033insG (p.Lys351X) Almost normal (17)
50
hF 4.9 c.896G>A (p.Arg299His) NA Neuro-logical — 878 ± 136 Abnormal (3.3) [34]
c.896G>A (p.Arg299His)
51
hF 4.7 c.896G>A (p.Arg299His) NA Family — 641 ± 74 Behavior
deterioration (3.7) [34]
c.896G>A (p.Arg299His)
56 F 39 c.896G>A (p.Arg299His) NA Hi met baby — 1233 ± 513 Neurological
abnormality c.896G>A (p.Arg299His)
60 F 6.1 c.895C>T (p.Arg299Cys) 20/20 NBS 800 –1067 1013 ± 283 Abnormal (1.4) [34, 40]
c.895C>T (p.Arg299Cys) Mild delay (5.6)
61 F 1.0 c.688G>A (p.Val230Met) NA /11 NBS 205 –328 84 ± 34 Abnormal (4.5) [82]
c.1067G>C (p.Arg356Pro) Neurologic normal
(5.5) 62 M 4.3 c.169G>A (p.Glu57Lys,
splicing?)
NA NBS 461 812 ± 309 Developmental
delay (2.3) MRI normal (2.3) Development normal (4.3) 63 M 2.9 c.169-2A>c.734_735delAG
(p.Gln245Profs*20)G
NA/0.3 NBS 938 –1271 905 ± 99 Abnormal (0.8)
c.791C>T (p.Arg264Cys) Worsen (1.5)
†
Patients are assigned the same identifiers as were used when they were first described in the following papers: patient 1 [14, 16]; patients 5, 7, 8, 9 and 13 [58];
patient 20: 14 [42]; patient 22 [38]; patient 29: patient 2 [44]; patient 30 [36]; patient 31 [41]; patient 32 [43]; patient 46: case 2 [15], and patient 61 [82]
*Activity based on assay of hepatic extract; others based on activity of mutant recombinant forms expressed in E coli [34]
a
Sibs are designated by the same superscript
†