‘Cerebrovascular disease related to
COL4A1 mutations in HANAC syndrome
S. Alamowitch, MD*
E. Plaisier, MD, PhD*
P. Favrole, MD
C. Prost, MD
Z. Chen, MSc
T. Van Agtmael, PhD
B. Marro, MD
P. Ronco, MD, PhD
Background: COL4A1 mutations cause familial porencephaly, infantile hemiplegia, cerebral small
vessel disease (CSVD), and hemorrhagic stroke. We recently described hereditary angiopathy
with nephropathy, aneurysm, and muscle cramps (HANAC) syndrome in 3 families with closely
localized COL4A1 mutations. The aim of this study was to describe the cerebrovascular pheno-
type of HANAC.
Methods: Detailed clinical data were collected in 14 affected subjects from the 3 families. MRI
and magnetic resonance angiography (MRA) were performed in 9 of them. Skin biopsies were
analyzed by electron microscopy in affected subjects in the 3 families.
Results: Only 2 of 14 subjects had clinical cerebrovascular symptoms: a minor ischemic stroke at
age 47 years and a small posttraumatic hemorrhage under anticoagulants at age 48 years. MRI-
MRA showed cerebrovascular lesions in 8 of 9 studied subjects (mean age 39.4 years, 21–57
years), asymptomatic in 6 of them. Unique or multiple intracranial aneurysms, all on the carotid
siphon, were observed in 5 patients. Seven patients had a CSVD characterized by white matter
changes (7/7) affecting subcortical, periventricular, or pontine regions, dilated perivascular
spaces (5/7), and lacunar infarcts (4/7). Infantile hemiplegia, major stroke, and porencephaly were
not observed. Skin biopsies showed alterations of basement membranes at the dermoepidermal
junction associated with expansion of extracellular matrix between smooth vascular cells in the
Conclusion: The cerebrovascular phenotype in hereditary angiopathy with nephropathy, aneu-
rysm, and muscle cramps syndrome associates a cerebral small vessel disease and a large vessel
disease with aneurysms of the carotid siphon. It is consistent with a lower susceptibility to hemor-
rhagic stroke than in familial porencephaly, suggesting an important clinical heterogeneity in the phe-
notypic expression of disorders related to COL4A1 mutations. Neurology®2009;73:1873–1882
CADASIL ? cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy; CPK ? creatine
phosphokinase; CSVD ? cerebral small vessel disease; DPS ? dilated perivascular spaces; HANAC ? hereditary angiopathy
with nephropathy, aneurysm, and muscle cramps; HERNS ? hereditary endotheliopathy with retinopathy, nephropathy, and
stroke; ICA ? intracranial aneurysm; MRA ? magnetic resonance angiography; OMIM ? Online Mendelian Inheritance in Man;
RVCL ? retinal vasculopathy with cerebral leukodystrophy; WMC ? white matter changes.
Type IV collagen is a major component of basement membranes. Type IV collagen ?1 and ?2
chains form the widely expressed ?1?1?2(IV) heterotrimers.1-3Mutations in the COL4A1
gene, which encodes the ?1(IV) chain, have been reported in 6 families with autosomal domi-
nant forms of porencephaly, in which a porencephalic cavity is caused by a cerebral hemorrhage
that occurred during the intrauterine or neonatal period.4-9A broad range of neurologic fea-
*These authors contributed equally to this work.
From the AP-HP, Tenon Hospital, Stroke Unit, Department of Neurology (S.A., P.F.), Paris, France; Universite ´ Pierre et Marie Curie–Paris 6 (S.A.),
France; AP-HP, Tenon Hospital, Department of Nephrology (E.P., P.R.), Paris, France; INSERM, U702 (E.P., Z.C., P.R.), Paris, France; Universite ´
Pierre et Marie Curie–Paris 6, UMRS702 (E.P., P.R.), France; AP-HP, Avicenne Hospital, Department of Dermatology (C.P.), Bobigny, France;
Faculty of Biomedical and Life Sciences (T.V.A.), University of Glasgow, UK; and AP-HP, Tenon Hospital, Department of Radiology (B.M.), Paris,
Supported by grants from INSERM, Universite ´ Pierre et Marie Curie–Paris 6 (BQR and legs Tessier), Assistance Publique–Ho ˆpitaux de Paris
(De ´le ´gation a ` la Recherche Clinique, Contrat CIRC), Association pour l’Utilisation du Rein Artificiel (AURA), Agence Nationale de le Recherche
(ANR-08-Genopath-018-02), and De ´le ´gation Ge ´ne ´rale a ` la Sante ´, and through Coordination Theme 1 (Health) of the European Community’s 7th
Framework Programme (grant agreement no. HEALTH-F2-2007- 201590). T.V.A. is supported by an MRC New Investigator Research Grant.
Disclosure: Author disclosures are provided at the end of the article.
Address correspondence and
reprint requests to Dr. Sonia
Alamowitch, Stroke Unit,
Department of Neurology, Tenon
University Hospital, AP-HP, 4
Rue de la Chine, Paris, France
Copyright © 2009 by AAN Enterprises, Inc.
tures have been described in families with he-
reditary porencephaly related to COL4A1
mutations, including infantile hemiplegia,
mental retardation, and hemorrhagic strokes
in childhood or in adults often triggered by
head trauma. The cerebrovascular phenotype
also includes a cerebral small vessel disease
(CSVD) with leukoencephalopathy, lacunar
infarcts, microbleeds, macrobleeds, and di-
lated perivascular spaces (DPS), sometimes
without porencephaly. Three additional fami-
lies with CSVD and COL4A1 mutations have
been reported, 1 with hemorrhagic stroke and
retinal arteriolar tortuosity, 1 with hemor-
rhagic stroke and cataract, and the other with
ischemic stroke and anterior segment dysgen-
esis of the eye (Axenfeld-Rieger anomaly).10-13
One sporadic case with recurrent intracerebral
hemorrhage was also reported.14No manifes-
tations suggestive of a systemic disease were
observed in these patients. Consequently,
COL4A1 mutations are a new cause of
CSVD, in addition to lipohyalinosis second-
ary to hypertension, and to other hereditary
conditions such as cerebral autosomal domi-
nant arteriopathy with subcortical infarcts
and leukoencephalopathy (CADASIL), reti-
nal vasculopathy with cerebral leukodystro-
phy (RVCL), and amyloid angiopathy.
We have recently described an autosomal
dominant syndrome in 3 unrelated French
families that we named HANAC syndrome
eurysm, and muscle cramps.15,16HANAC syn-
drome is due to COL4A1 mutations affecting
glycine residues that are in close proximity in
exons 24 and 25 within the triple-helix domain
of the protein. HANAC syndrome has a broad
phenotypical spectrum with systemic as well as
cerebrovascular features. The systemic pheno-
type includes a nephropathy with either hema-
turia or bilateral renal cysts, a muscular disease
with cramps and/or elevated creatine phos-
phokinase (CPK), and retinal arterial tortuosity.
Because ultrastructural examination of the kid-
ney and the skin shows abnormal thickening,
multilamination, and/or focal disruption of the
a systemic “basalopathy.” The objective of the
present study is to give a detailed description of
neurologic manifestations and brain imaging in
the 3 recently reported families with HANAC
METHODS A total of 14 affected members have been identi-
fied in the 3 families (A, B, and C) with HANAC syndrome
(figure e-1 on the Neurology®Web site at www.neurology.org).
As previously reported, genetic analysis showed COL4A1 muta-
tions localized in exon 24 in family A (c.1493G?T) and in exon
25 in family B (c.1555G?A) and family C (c.1583G?A).16
Standard protocol approvals, registration, and patient
consents. The study received approval from the ethical regional
committee on human experimentation (“Comite ´ de Protection
des Personnes-Ile de France VI number P061017–IDRCB
2007-A01441-52). Written informed consent was obtained
from all patients participating in the study.
Clinical data. Nine of the 14 patients with COL4A1 muta-
tions were directly interviewed and examined for neurologic
evaluation: 3 affected brothers and their 3 children in family A, 2
patients in family B (the father and her daughter), and 1 patient
in family C. Clinical information on the 4 deceased patients and
on the affected subjects who declined to participate in this study
was obtained through their relatives. The neurologic interview
recorded mental retardation, infantile hemiparesis, strokes and
their types, cranial traumas and their consequences, headaches,
epilepsy, dementia, and sudden death. Risk factors for cerebral
vascular disorders were recorded.
Clinical evaluation of systemic involvement, including renal,
muscle, eye, and cardiovascular symptoms, has been reported in
detail.16All 14 patients and 3 relatives without COL4A1 muta-
tion (B.III-2, B.II-1, and C.III-2) had fundus examination and
Cerebral imaging. Brain MRI was performed in 9 patients
and in 1 unaffected relative (C.III-2) using a 1.5-T magnetic
resonance scanner (contiguous slices of 5 mm thickness) and
included T1-weighted images, T2-weighted images, fluid-
attenuated inversion recovery sequences, and magnetic reso-
nance angiography (MRA). T2 gradient-echo (T2*) weighted
images were recorded in 7 patients. When MRA was inconclu-
sive about the presence of an intracranial aneurysm (ICA), 16-
row multislice CT angiography was performed. Four-axis
conventional angiography was available in 1 patient.
All imaging data were analyzed by a consensus of 2 neurolo-
gists (S.A. and P.F.) and 1 neuroradiologist (B.M.). The follow-
ing lesions were assessed: white matter changes (WMC) defining
leukoencephalopathy, lacunar infarcts, DPS, microbleeds, mac-
robleeds, and porencephaly. MRI lesions were categorized by
anatomic cerebral region (appendix e-1). For lobar white matter,
it was specified when lesions affected the arcuate fibers and the
center semiovale. WMC were rated according to the Scheltens
visual scale, taking into account size, number, and anatomic dis-
tribution of the lesions17(appendix e-1). The numbers of lacunar
infarcts and microbleeds were recorded.
The size of each ICA was defined by its maximal diameter.
The carotid siphon was divided according to Fisher classification
into 5 segments from its beginning to its end with 3 extradural
(C5 to C3) and 2 intradural (C2 and C1) segments. Other intra-
cranial arteries abnormalities, such as dolichoectasia, were also
Skin biopsy. A punch biopsy was performed in healthy skin of
subjects A.III.3, A.IV.4, B.II.1, and C.II.3 (with the COL4A1
Neurology 73December 1, 2009
mutation) and C.III.2 (without the mutation). Electron micros-
copy was performed as previously described.16
RESULTS Clinical data. None of the 14 subjects
had infantile hemiparesis or mental retardation.
There was no history of stroke during the neonatal
period and childhood, or history of spontaneous sub-
arachnoid or intracerebral hemorrhage or dementia
in the 3 families. None of the 14 subjects had diabe-
tes or hypertension, 1 patient had hypercholesterol-
emia (A.III.1), 2 subjects were past smokers (A.III.1
and A.III.3), and 1 was an active smoker (A.III.5).
Neurologic examination was normal for CNS func-
tions in the 9 subjects whom we directly assessed. For
the 4 deceased subjects, the age of death ranged from
60 to 69 years. The causes of death were not neuro-
logic. Subject A.II.1, whose genotype is unknown,
died suddenly at age 6 months from an unknown
cause. No other sudden death was recorded.
One patient (A.IV.4) had a unique seizure at age 19
years without recurrence in the absence of any therapy.
Three subjects (A.III.1, A.IV.1, and C.II.3) had mi-
graine without aura. Only 2 of the 14 subjects with
jury. Patient A.III.3 had an acute cerebellar ataxia with-
out vertigo lasting 2 days at age 47 years; MRI with
diffusion-weighted imaging, performed only 8 days
later, did not show any recent infarct. The diagnosis of
brainstem minor ischemic stroke was retained, and in-
vestigations revealed neither cardiac nor large artery
cause. Patient A.III.1 presented a posttraumatic cere-
tient was receiving anticoagulants
thrombosis of the lower limb. A cranial trauma was in-
deed responsible for confusion, aphasia, and headaches
related to a left temporal hemorrhagic contusion mea-
His mental status improved within 24 hours, and his
language totally recovered within 4 weeks. Notably, his
crash at age 30 years, with initial loss of consciousness
and transient confusion lasting 1 day. No CT scan was
performed. He denied any persistent neurologic deficit.
All patients showed retinal arteriolar tortuosity and
had muscle cramps, with elevation of CPK, whereas 3
relatives without COL4A1 mutation did not have any
retinal or muscular abnormalities.16Renal involvement
was observed in 10 patients, consisting of renal cysts in
4, hematuria in 7 (family A), and renal insufficiency in
5. Raynaud phenomenon was recorded in 6 patients,
and supraventricular arrhythmia was recorded in 5.16
Radiologic data. Brain MRI was performed in 9 sub-
jects (mean age 39.4 years, 21–57 years), during the
third decade of life in 4 of them and during the fifth
and sixth decades in the other 5 patients. All but 1
affected subject (A.III.5, aged 44 years) showed at
least 1 abnormality. Four patients had a combination
of ICAs and CSVD, 3 had only CSVD, and 1 had an
isolated ICA (tables 1 and e-1). Interestingly, no
porencephaly was observed. Brain imaging per-
formed in 1 unaffected relative (C.III.2) was normal.
Table 1 White matter changes and other components of cerebral small vessel disease on brain MRI
White matter changes
Lacunar infarct topography (n)
spaces topographyMicrobleed topography (n)
23 Yes (6) Yes (11)Yes (6) RL lenticular N (3)RL basal ganglia R lenticular N (1)
R cerebellar hemisphere (1)
22 Yes (6)Yes (13)Yes (3) RL CSO (2), RL lenticular N (3)RL basal gangliaL CSO (1)
L cerebellar hemisphere (1) L cerebellar hemisphere (1)
0 No (0)No (0)No (0)NoNo No
1 No (0) Yes (1)No (0)NoNoNo
8 No (0)Yes (8) No (0) RL CSO (2) RL basal gangliaNo
9 Yes (2)Yes (7) No (0)No NoNo
11Yes (4)Yes (7)No (0) RL CSO (3) RL CSO, RL basal gangliaNA
0 No (0)No (0)No (0)NoNo NA
13Yes (4) Yes (4)Yes (5) NoRL basal ganglia R cerebellar hemisphere (1)
5/97/9 3/9 4/95/9 3/7
SS ? Schelten score; lenticular N ? lenticular nucleus; CSO ? center semiovale; NA ? not applicable.
Neurology 73December 1, 2009
A total of 12 ICAs were present in the 5 subjects
with at least 1 affected member in each family: 3 of 6
in family A (A.III.3, AIV.2, and A.IV4), 1 of 2 in
family B (B.III.2), and 1 of 1 in family C (C.II.3)
(figure 1 and table e-1). Multiple ICAs were observed
in 3 patients. All ICAs were asymptomatic and dis-
covered on systematic radiologic examinations at
ages ranging from 21 to 57 years. The majority of
ICAs were small; only 1 was larger than 7 mm. The
ICAs presented a large base of implantation without
identifiable neck. All were localized on the intracra-
nial carotid, at different levels of the carotid siphon.
Figure 1 Intracranial aneurysms in HANAC syndrome
Intracranial aneurysms (arrows) or dolichoectasia (star) are shown in the 5 patients of the 3 families. Conventional angiog-
raphy demonstrates multiple aneurysms on the right distal carotid artery in patient A.III.3 (A). Note an aspect of dolichoar-
teries of the carotid siphon. Magnetic resonance angiography (MRA) on axial slice (B) shows an aneurysm of the right distal
carotid artery in patient A.IV.2. CT angiography (C) demonstrates 2 aneurysms of the right distal carotid artery with the
form of glove finger in patient A.IV.4. (D) shows a right distal carotid aneurysm on axial slice of MRA in patient B.III.2. CT
angiography shows multiple intracranial aneurysms of the right carotid arteries (E) and dolichoectasia (F) of the left distal
carotid artery in patient C.II.3. HANAC ? hereditary angiopathy with nephropathy, aneurysm, and muscle cramps.
Neurology 73 December 1, 2009
Six ICAs were extradural (1 on C4 and 5 on C3), and
6 were intradural (4 on C2 and 2 on C1). Eleven of
the 12 aneurysms were localized on the right carotid,
and 1 was localized on the left carotid. Additionally,
2 patients (A.III.3 and C.II.3) had dolichosiphons of
Seven patients had MRI abnormalities consistent
with a CSVD, including 5 of 6 in family A (A.III.1,
A.III.3, A.IV.3, A.IV2, and A.IV.4), 1 of 2 in family
B (B.II.1), and 1 of 1 in family C (C.III.3). All these
7 patients had WMC with a periventricular (5/7),
subcortical (7/7), and/or subtentorial (3/7) distribu-
tion (table 1). Periventricular WMC showed an
equal distribution between anterior, posterior, and
lateral horns (figure 2). Subcortical WMC especially
affected the frontal and parietal lobes, with the larg-
est and most confluent lesions being observed in the
inferoposterior areas of these lobes. Temporal and
occipital lobes as well as U fibers were globally
spared. WMC were predominantly located in the
centrum semiovale and sometimes involved the ex-
ternal capsule and the posterior part of the posterior
limb of the internal capsule (figure 2). Subtentorial
WMC affected the core of the pons respecting the
surface (figure 2). No cortical involvement was
noted. In addition, 15 lacunar infarcts were observed
in 4 patients (A.III.1, A.III.3, A.IV.2, and B.II.1),
including 9 located in white matter (7 in the centrum
Figure 2 White matter changes
Fluid-attenuated inversion recovery (FLAIR) images show multiple periventricular and subcortical cerebral white matter
changes in patients A.III.1 at age 51 years (A), A.III.3 at age 48 years (B), A.IV.2 at age 24 years (C), A.IV.4 at age 24 years
(D), B.II.1 at age 57 years (E), and C.II.3 at age 57 years (F). FLAIR images denote subtentorial white matter changes of the
rostral pons in patients A.III.1 (G), A.III.3 (H), and C.II.3 (I).
Neurology 73 December 1, 2009
semiovale and 2 in cerebellum hemisphere) and 6 in
gray matter, all in the lenticular nucleus (table 1 and
figure e-2). Five patients (A.III.1, A.III.3, A.IV.2,
B.II.1, and C.II.3) had DPS in the basal ganglia
and/or centrum semiovale (table 1 and figure e-2).
Interestingly, only 3 (A.III.1, A.III.3, and C.II.3) of the
7 subjects investigated by T2* sequences had microb-
leeds, with 1 or 2 microbleeds per patient (table 1 and
figure e-2). Patient A.III.1 had a 10-mm posttraumatic
hemorrhagic lesion of the left external temporal region,
but no other patient had a macrobleed.
Globally, CSVD seemed more severe in older
than in younger patients; the Scheltens score was
generally higher in the oldest generation (table 1).
However, the severity of WMC was not homoge-
neous among patients of the same age. Indeed, the
44-year-old patient A.III.5 did not have any MRI
abnormalities. Moreover, the 29-year-old patient
A.IV.1 had very mild WMC in comparison with his
24-year-old brother (A.IV.2).
Ultrastructural skin arterial lesions. Significant ultra-
structural anomalies were found in affected subjects
although their skin had a completely normal appear-
ance on physical examination and light microscopy.
Replication of the lamina densa was observed at the
dermoepidermal junction in the affected subjects of
the 3 families (A.III.3, A.IV.4, B.II.1, and C.II.3;
figure 3, A–C). The wall of dermal arterioles was also
markedly altered. Vascular smooth muscle cells were
dissociated, with abnormal spreading of the base-
ment membrane (figure 3, D–F). The vessel wall had
a normal appearance in the skin of a control sample,
unaffected subject C.III.2 (data not shown).
Figure 3 Skin basement membrane abnormalities
Ultrastructural examination of skin biopsies in affected patients of the 3 families (A.IV.4 [A and D], B.II.1 [B and E], and C.II.3 [C and F]) shows segmental
basement membrane (BM) replications at the dermoepidermal junction (arrow, A–C). In dermal vessels, vascular smooth muscle cells are dissociated by
abnormal expansion and thickening of the BM (open arrow and asterisk, D–F).
Neurology 73 December 1, 2009
DISCUSSION Since the initial description of 3 dis-
tinct phenotypes associated with COL4A1 mutations
that include autosomal dominant type I poren-
cephaly (Online Mendelian Inheritance in Man
[OMIM] 175780), cerebral small vessel disease with
hemorrhages (OMIM 607595), and HANAC syn-
drome (OMIM 611773), identification of additional
families now clearly indicates that autosomal domi-
nant porencephaly and CSVD are part of a contin-
uum with overlapping neurologic clinical and
imaging features (table 2). This study focused on ce-
rebrovascular disease in HANAC syndrome and re-
vealed 4 distinctive features. First, although
cerebrovascular lesions are common, they are usually
asymptomatic in contrast with patients with promi-
nent brain disease related to COL4A1 mutations, in
whom various degrees of infantile hemiplegia, men-
tal retardation, and stroke were commonly observed.
Second, in addition to CSVD dominated by leu-
koencephalopathy, MRI analysis revealed unique or
multiple aneurysms electively localized on the carotid
siphon, which indicates that mutations in COL4A1
are not only involved in CSVD but also in large ar-
tery disease. Third, no patient with HANAC syn-
drome displayed porencephalic cavities, macrobleed,
or a large number of microbleeds. Fourth, cerebro-
vascular disease in HANAC is part of a multiorgan
disease with systemic vasculopathy as attested to by
the results of skin biopsy.
In human and mice mutants with porencephaly
related to COL4A1 mutation, the phenotype in-
cludes a high susceptibility to hemorrhagic strokes
frequently triggered by birth trauma, brain trauma,
or anticoagulant treatment.4,11By contrast, in
HANAC syndrome, only 1 of the 14 affected mem-
bers had a small hemorrhage after a serious head
trauma despite anticoagulant therapy. Another sub-
ject had a severe head trauma without any trace of
cerebral hemorrhage on follow-up MRI. These find-
ings strongly suggest that COL4A1 mutations under-
lying HANAC syndrome are associated with a lower
risk of hemorrhagic strokes than COL4A1 mutations
underlying familial porencephaly and CVSD. The
absence of severe brain hemorrhages may be due to
environmental and/or genetic modifiers. Mice with
COL4A1 mutations also show important phenotypic
heterogeneity,4,18with a significant influence of the
genetic background on the ocular phenotype.19Be-
cause of the small number of families and patients
with COL4A1 mutations described so far, a precise
Table 2 Phenotypic and genotypic characteristics of families with COL4A1-related disorders
aneurysms RAT Other
Raynaud phenomenaExon Nucleotide
24 c.1493G?T p.G498V16
25 c.1555G?A p.G519R16
25 c.1583G?A p.G528E16
Brain and eye restricted phenotype
25 c.1769G?A p.G562E10, 11
29 c.2159G?A p.G720D12
29c.2245G?A p.G749S4, 6
30 c.2263G?A p.G755R13
39c.3389G?A p.G1130D 5, 7
43 c.3706G?A p.G1236R 4, 8
*One of the 5 affected members of the family had an asymptomatic aneurysm of the right carotid artery.
†One (aged 37 y) of the 5 affected members of the family had an asymptomatic aneurysm of the top of the basilar artery.
Ref ? reference; CSVD ? cerebral small vessel disease; RAT ? retinal arteriolar tortuosity; HANAC ? hereditary angiopathy with nephropathy, aneurysm,
and muscle cramps; IS ? ischemic stroke; ND ? not done; ICH ? intracranial hemorrhage; Ax-Rieger ? Axenfeld-Rieger anomaly.
Neurology 73December 1, 2009
genotype-phenotype correlation with neurologic as
well as systemic manifestations remains hazardous.
Nevertheless, our data raise the hypothesis of a muta-
tion effect on the phenotypic expression, because
COL4A1 mutations responsible for HANAC syn-
drome are closely localized in a very narrow stretch of
the gene, whereas other mutations usually affect
more C-terminal glycine residues (table 2).
CSVD in HANAC syndrome is dominated by leu-
koencephalopathy affecting periventricular, deep re-
gions and the pons. WMC were noted despite the
young age of the patients and in the absence of vascular
risk factors, such as hypertension, usually associated
with WMC.20The highest lesion load was observed in
frontal and parietal white matter predominantly in pos-
terior regions, especially in the centrum semiovale. The
temporal lobe and arcuate fibers are spared in contrast
with the abnormalities observed in CADASIL.21,22
Most of the WMC and lacunar infarcts were located in
leptomeningeal long penetrating arteries, and pontine
perforating arteries with a pattern recovering partially
those of WMC associated with hypertension and
The severity of WMC seems to be variable be-
tween and within families with HANAC, suggest-
ing the presence of genetic and/or environmental
modifiers or subtle differences in the consequences
of the different mutations. In a previously re-
ported family of 6 affected members with a
COL4A1 mutation but without HANAC disease,
2 subjects died of intracranial hemorrhage,
whereas MRI signal abnormalities did not change
after a follow-up period of 7 years in the other
patients.24These findings correspond with our
data showing that COL4A1 mutation carriers may
have a great diversity in clinical and radiologic ex-
pression of cerebrovascular injury.
COL4A1 mutations in HANAC syndrome con-
stitute a new monogenic cause of familial ICAs with
55% of the affected patients. ICAs were previously
described in only 3 patients from 3 different families
with COL4A1 mutation but without HANAC syn-
drome5,7,12,13(table 2). The other hereditary diseases
associated with ICAs are rare and consist mainly of
diseases of connective tissue and extracellular ma-
trix such as autosomal dominant polycystic kidney
disease and Ehlers-Danlos syndrome type IV with
mutations in COL3A1.24-26The extracellular ma-
trix of the arterial wall plays an important role in
strength and elasticity of intracranial arteries. Col-
lagen types III and IV and elastin fibers are de-
creased in the wall of ICAs as well as in skin
biopsies of patients with ICA.27Moreover, genes
encoding extracellular matrix protein, including
COL4A1, have been associated with a susceptibil-
ity to ICA formation in the general population.28
In vascular basement membrane, COL4A1 forms
a sheetlike network beneath the endothelium and
surrounding smooth muscle cells.1,2Our findings
suggest that COL4A1 mutations observed in
HANAC syndrome lead to a disruption of extra-
cellular matrix and a remodeling of the vascular
wall with the formation of ICA.
A surprising fact about ICAs in HANAC syn-
drome was their elective localization on the carotid
siphon both on intradural and extradural segments.
The collagen type IV network is essential for the co-
hesiveness of basement membranes under conditions
of increasing mechanical demands.29The carotid si-
phon constitutes a peculiar zone due to the conjunc-
tion of a high blood flow and a tortuous curving
form. In HANAC syndrome, the occurrence of base-
ment membrane defects in this area, which is subject
to high mechanical stress, may predispose to ICA for-
mation in the carotid siphon. Intriguingly, no pa-
tient had a spontaneous subarachnoid hemorrhage,
which may be due to the small size of these ICAs or
to a low risk of rupture of aneurysms associated with
In addition to CSVD and ICA, COL4A1 muta-
tions in HANAC syndrome are responsible for a
multiorgan disease affecting the kidney, the muscula-
ture, and the retinal small arterioles, which seems to
be the hallmark of the syndrome. The ultrastructural
alterations observed in the skin, particularly in der-
mal arterioles, demonstrate a systemic vasculopathy.
Interestingly, skin biopsy also shows changes in
blood vessel morphology in 2 autosomal dominant
cerebral angiopathies: CADASIL (OMIM 125310)
due to mutations in the NOTCH3 receptor and he-
reditary endotheliopathy with retinopathy, nephrop-
athy, and stroke (HERNS), a distinctive subtype of
RVCL caused by mutations in TREX1 transcription
factor.30,31Patients with CADASIL and transgenic
mice expressing mutant Notch3 show an enlargement
of the inter–smooth muscle cell space, in skin vessels
and tail artery sections. These anomalies precede the
accumulation of granular osmiophilic material in
transgenic mice.32In HERNS, the brain disease is
associated with renal abnormalities, Raynaud phe-
nomenon, and retinal vasculopathy with ultrastruc-
tural alterations affecting capillaries in the brain
and other tissues,33but with a distinct feature from
HANAC syndrome. Skin biopsy may provide a
cost-effective guide before practicing an expensive
and time-consuming genetic screening of COL4A1
Neurology 73December 1, 2009
Sonia Alamowitch and Emmanuelle Plaisier designed the study, retrieved
the data, and drafted the report. Pascal Favrole and Be ´atrice Marro re-
trieved the clinical and radiologic data. Catherine Prost and Zhiyong
Chen retrieved the data of skin biopsy. Tom Van Agtmael helped with the
interpretation of the data. Pierre Ronco initiated the project and contrib-
uted to design and revision of the report.
The authors thank Safa Benhassine and Marie-Chrisine Verpont for tech-
Dr. Alamowitch serves on the editorial committee of the Revue Neu-
rologique. Dr. Plaisier, Dr. Favrole, Dr. Prost, and Mrs. Chen report no
disclosures. Dr. Van Agtmael receives research support from the Medical
Research Council UK [G0601268 (PI)]. Dr. Marro reports no disclo-
sures. Dr. Ronco serves as a Section Editor for Nephrology Dialysis Trans-
plantation and serves on the editorial boards of the Journal of American
Society of Nephrology, Nature Clinical Practice Nephrology, and Kidney In-
ternational; and has received research support from Amgen SAS.
Received April 19, 2009. Accepted in final form September 9, 2009.
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Editor’s Note to Authors and Readers: Levels of Evidence coming to Neurology®
Effective January 15, 2009, authors submitting Articles or Clinical/Scientific Notes to Neurology®that report on clinical
therapeutic studies must state the study type, the primary research question(s), and the classification of level of evidence assigned
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translated into classes of recommendations for clinical care, as shown below (right). For more information, please access the
articles and the editorial on the use of classification of levels of evidence published in Neurology.1-3
1. French J, Gronseth G. Lost in a jungle of evidence: we need a compass. Neurology 2008;71:1634–1638.
2. Gronseth G, French J. Practice parameters and technology assessments: what they are, what they are not, and why you should care. Neurology
3. Gross RA, Johnston KC. Levels of evidence: taking Neurology®to the next level. Neurology 2008;72:8–10.
Neurology 73 December 1, 2009