A Japanese family of autosomal dominant cerebral small vessel disease with heterozygous HTRA1 mutation showing dementia, gait disturbance and subarachnoid hemorrhage

Abstract

Homozygous mutations of high temperature requirement A serine peptidase 1 (HTRA1) gene cause an autosomal recessive cerebral small vessel disease, namely cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL). Meanwhile, heterozygous mutations of the HTRA1 can also cause an autosomal dominant small vessel disease with a milder clinical phenotype. Here we described 2 patients in a Japanese family with the same heterozygous HTRA1 mutation (c.496 C>T, p.R166C), showing a unique clinical history of traumatic subarachnoid hemorrhage (SAH), no alopecia or spondylosis, in addition to previously similar clinical phenotypes such as cognitive impairment, gait disturbance, and hyperreflexia. The present cases suggest that traumatic SAH may be an important risk of the heterozygous HTRA1 mutation (c.496 C>T, p.R166C), especially in Asia.

 Abbreviations

CARASIL, cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy; DSWMH, deep and subcortical white matter hyperintensity; FLAIR, fluid-attenuated inversion recovery; HTRA1, high temperature requirement A serine peptidase 1; MCA, middle cerebral artery; MMSE, mini-mental state examination; MRI, magnetic resonance imaging; PCR-RFLP, PCR-restriction fragment length polymorphism; PVH, periventricular hyperintensity; SAH, subarachnoid hemorrhage; SPECT, single photon emission computed tomography; TGF-β, transforming growth factor-β; TIA, transient ischemic attack; yo, years old.

 Introduction

High temperature requirement peptidase A1 (HTRA1) is a serine protease, which inhibits transforming growth factor β (TGF-β) signaling pathway¹. Homozygous mutations of the HTRA1 gene cause a hereditary cerebral small vessel disease characterized by leukoencephalopathy, early-onset alopecia and lumber spondylosis, and referred to as cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL)^{2, 3}. However, recent evidence noted that heterozygous mutations of HTRA1 could also cause small vessel disease with a dominant inheritance pattern^4-6. Here we described 2 patients in a Japanese family with the heterozygous HTRA1 mutation (c.496 C>T, p.R166C) showing a unique clinical history of traumatic SAH different from previous reports.

 Case Reports

Patient II-4 is a 77-year-old (yo) man. When he was 71, he experienced a sudden episode of vertigo that disappeared within 2 days. He was aware of gait disturbance at 73 yo, which became more severe at 75 yo and cognitive function was impaired, but he did not show alopecia or lumbar spondylosis. He visited a local hospital where old multiple lacunar infarctions were detected in brain magnetic resonance imaging (MRI), and then drug treatment started with clopidogrel (75 mg). He was a non-smoker and his blood pressure was normal at 117/70 mmHg. His cognitive function was impaired to mini-mental state examination (MMSE) score of 12/30 and Hasegawa dementia scale-revised score of 7/30. Affective function was also diminished, showing Abe’s BPSD score of 8/44. Neurological examination showed hyperreflexia and slight cogwheel rigidity (R>L) in all extremities, but no evident pathological reflexes or sensory disturbances in his extremities. A fluid-attenuated inversion recovery (FLAIR) image of MRI showed hyperintensity in the periventricular white matter with atrophic splenium of corpus callosum (Fig. 1b & 1c, an arrow), whereas the tip of the temporal lobe was spared. At 77 yo, he stumbled and received a blow to the left side of his head, when a slight traumatic subarachnoid hemorrhage (SAH) was detected by head CT scan (Fig. 1d, an arrowhead). Despite this, he recovered within 3 days without sequela.

Figure 1. (a) Family tree of the patients. (b, c) FLAIR images of patient II-4 showing white matter hyperintensities with atrophic corpus callosum (an arrow). (d) Head CT of patient II-4 detecting a slight SAH on the surface of the left temporal lobe (an arrowhead). (e) MR angiography of patient III-1 showing no evident stenosis of the major artery. (f, g) FLAIR images of patient III-1 pointing out diffuse hyperintensities involving periventricular and deep white matter with atrophic corpus callosum (an arrow). (h) Head CT of patient III-1 showing a massive SAH (arrowheads) with right subdural hematoma (an arrow).

Patient III-1 is a 56 yo man, the proband of the present family, and a nephew of patient II-4. His mother, who also showed cognitive dysfunction, was diagnosed with Alzheimer’s disease in a local hospital at 79 yo, and died of aspiration pneumonia at 85 yo. At 53 yo, he experienced an acute episode of dysarthria and visited a local hospital, where multiple small infarctions were pointed out in the left middle cerebral artery (MCA) territory on a brain MRI. Drug treatment with aspirin (100 mg) started, and the above symptom resolved in a week. At 56 yo, he displayed dysarthria once again and newly obtained gait disturbance and cognitive dysfunction. When he visited our hospital, he did not show alopecia or lumbar spondylosis. He was a non-smoker and his blood pressure was normal at 125/90 mmHg. His cognitive function was mildly impaired with MMSE score of 26/30, Hasegawa dementia scale-revised score of 21/30, frontal assessment battery score of 9/18, and Montreal cognitive assessment score of 23/30. He was depressive with geriatric depression scale of 10/15, and apathetic with apathy score of 23/42, but no BPSD showing Abe’s BPSD score of 0/44. A neurological examination showed dysarthria as well as hyperreflexia in all extremities, but no evident pathological reflexes nor sensory disturbances in his extremities. Serum analysis showed normal LDL-cholesterol (128 mg/dl, normal 65-165 mg/dl), triglycerides (71 mg/dl, normal 40-234 mg/dl), fasting blood glucose (100 mg/dl, normal 73-109 mg/dl), HbA1c (5.7%, normal 4.9-6.0%), homocysteine (10.3 nmol/ml, normal 3.7-13.5 nmol/ml), protein C activity (115%, normal 64-146%), and protein S (95%, normal 60-150%). Serum very long chain free fatty acids were also normal. A cerebrospinal fluid examination revealed 1 leucocyte/μl with 100% mononucleosis and normal glucose (58 mg/dl) but an increased level of protein (78 mg/dl). The MRI (FLAIR) images showed hyperintensity in the deep and periventricular white matter with atrophic splenium of corpus callosum (Fig. 1f & 1g). Despite no significant stenosis in the major artery (Fig. 1e), cerebral blood flow showed hypoperfusion of bilateral frontal lobes, bilateral parietal lobes, and the left temporal lobe (Fig. 2). Due to this small vessel disease, cilostazol (100 mg) was added to aspirin. However, at 58 yo, after he fell and hit his head on the floor, CT scan showed a massive traumatic SAH (Fig.1h, arrowheads) with right subdural hematoma (Fig.1h, arrow). Despite craniotomy to remove the hematoma, he deceased.

Figure 2. ^99mTc-ECD-single photon emission computed tomography (SPECT) of patient III-1 shows hypoperfusion of bilateral frontal lobes, bilateral parietal lobes, and the left temporal lobe.

For DNA analysis, written informed consent was obtained from the father and the 2 affected patients with approval of the research ethics committee of Okayama University (#329) and Niigata University (#802). Genomic DNA was extracted from the peripheral blood leukocytes of the father and both patients, and Sanger sequence analysis of CSF1R (exons 12-22) and Notch3 (exons 2-24) were performed only in Patient III-1, but were normal. Then direct sequencing of HTRA1 exons with the Sanger method was performed in the father and the 2 affected patients as previously reported⁶. Both affected patients showed a heterozygous point mutation from C to T coding 496, resulting in substitution of the 166th arginine to cysteine located in exon2 of the HTRA1 gene (c.496 C>T, p.R166C) (Fig. 3a). The point mutations of c.496 C>T in HTRA1 were confirmed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) with Hha I, and an uncut PCR product band (276 bp) was detected in both patients (Fig. 3b). Based on the above data, we diagnosed the 2 patients as having an autosomal dominant cerebral small vessel disease with heterozygous HTRA1 mutation (c.496 C>T, p.R166C).

Figure 3. (a) The 2 patients (II-4 and III-1) carried the same heterozygous point mutation from C to T coding 496 (arrowheads), resulting in substitution of the 166th arginine to cysteine located in exon2 of the HTRA1 gene. (b) A point mutation of c.496 C>T (p.R166C) in HTRA1, confirmed by PCR-RELP with Hha I. An uncut PCR product band was found in both patients even after Hha I digestion (an arrowhead).

 Discussion

Here we described 2 patients in a Japanese family with similar clinical phenotypes such as cognitive impairment, gait disturbance, hyperreflexia, history of traumatic SAH without alopecia or spondylosis, caused by a heterozygous HTRA1 mutation (c.496 C>T, p.R166C). The same p.R166C mutation was previously reported in Greece⁴, in which a patient of heterozygous HTRA1 mutation (p.R166C) showed cognitive impairment, gait disturbance, hyperreflexia and alopecia without spondylosis (Table 1). Although the same heterozygous HTRA1 mutation may cause a different clinical spectrum, the present Japanese cases showed a unique clinical history of traumatic SAH, different from the Greek case (Table 1).

Table 1. Characteristics of Patients

	Case II-4	Case III-1	Bougea et al. (2017)
Heterozygous HTRA1 mutation	c.496 C>T (p. R166C)	c.496 C>T (p. R166C)	c.496 C>T (p. R166C)
Gender	M	M	M
Age at onset, y	71	53	29
Age at examination, y	77	56	31
Duration of illness, y	4	3	2
Family history	+	+	+
Hypertension	–	+	–
Hyperlipidemia	–	+	–
Smoking	–	–	–
Initial symptom	gait disturbance	dysarthria and dysphasia	migraine
History of TIA or ischemic stoke	+	+	–
History of traumatic SAH	+	+	–
Cognitive impairment(MMSE)	12	± (26)	24
Gait disturbance	+	+	+
Hyperreflexia	+	+	+
Alopecia	–	–	+
Spondylosis	–	–	–
Hearing loss	–	–	+
PVH	+	+	+
DSWMH	+	+	+
Multiple lacunar infarcts	+	+	+
Microbleeds	–	–	–

TIA, transient ischemic attack; SAH, subarachnoid hemorrhage; MMSE, mini-mental state examination; PVH, periventricular hyperintensity; DSWMH, deep and subcortical white matter hyperintensity.

HTRA1 is a serine protease that represses the transforming growth factor β (TGF-β) signaling pathway, whereas mutated HTRA1 cannot repress the production of TGF-β. As a result, overproduced TGF-β is believed to cause cerebral small vessel disease characterized by recurrent ischemic stroke, multiple lacunar infarctions, and leukoencephalopathy^1,3. In patients with a homozygous/heterozygous HTRA1 mutation, cerebral small vessels show pathological changes such as initial thickening with fibronectin, splitting of the elastic lamina and loss of smooth muscle cells^7,8, which has been assumed to induce cerebral ischemia. However, Asian patients, including Taiwanese, Chinese, and Japanese with heterozygous HTRA1 mutations, sometimes showed intracerebral hemorrhage^9-11, indicating that the HTRA1 mutation may cause vulnerability of cerebral artery. In fact, both Japanese patients in this paper developed traumatic SAH, although use of anti-platelet drugs may also be related. Hemorrhagic stroke is more common in Asian people than in Caucasian¹², so intracerebral hemorrhage and traumatic SAH may be a greater and/ or important risk of heterozygous HTRA1 mutation (c.496 C>T, p.R166C) in Asian patients than in Caucasian.

 Conflicts of interest

The authors disclose no potential conflicts of interest.

 Acknowledgements

This work was partly supported by a Grant-in-Aid for Scientific Research (B) 17H04196, (C) 17K10827 and Challenging Research 15K15527, and by Grants-in-Aid from the Research Committees (Mizusawa H, Nishizawa M, Sasaki H, and Aoki M) from the Ministry of Health, Labour and Welfare of Japan.

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