Acta Neuropathol (1996) 92 : 312–318

© Springer-Verlag 1996

C A S E R E P O RT

M. Kaido · H. Fujimura · F. Soga · K. Toyooka ·
H. Yoshikawa · T. Nishimura · T. Higashi · K. Inui ·
H. Imanishi · S. Yorifuji · T. Yanagihara

Alzheimer-type pathology in a patient with mitochondrial myopathy,
encephalopathy, lactic acidosis and stroke-like episodes (MELAS)

Received: 30 January 1996 / Revised, accepted: 26 March 1996

Abstract A 53-year-old Japanese woman with a point
mutation in mitochondrial DNA (tRNALeu(UUR), nt3243)
consistent with mitochondrial myopathy, encephalopathy,
lactic acidosis and stroke-like episodes (MELAS) and
Alzheimer-type brain pathology is reported. This woman
had suffered myopathy and psychosis without any clinical
evidence of, stroke-like episodes during the last 10 years
of her life, and had died after an accident. At autopsy 30 h
post mortem, a part of the brain was snap frozen for biochemical and histochemical studies, and the remaining part
was processed for a routine examination and electron microscopy. In the brain there were no ischemic lesions. Instead, primitive/diffuse senile plaques were found throughout the brain, predominantly in the frontal and temporal
lobes, while Alzheimer neurofibrillary tangles were found
only in the parahippocampal gyrus. These plaques were
positive for β-protein and mostly negative for tau protein,
ubiquitin, neurofilaments, α-choline acetyltransferase, and
acetylcholinesterase. Mutations in codon 331 of the ND2
gene as well as codons 693, 713 and 717 of the β-amyloid
precursor protein gene, known to be responsible for some
cases of familial Alzheimer disease, were not found. Furthermore, coincidental Down syndrome was ruled out by

M. Kaido · H. Fujimura · F. Soga · K. Toyooka · H. Yoshikawa ·
T. Nishimura · S. Yorifuji · T. Yanagihara
Department of Neurology, Osaka University Medical School,
Osaka, Japan
K. Inui
Department of Pediatrics, Osaka University Medical School,
Osaka, Japan
T. Higashi
The First Department of Internal Medicine,
Osaka Teishin Hospital, Osaka, Japan
H. Imanishi
Department of Pediatrics, Osaka Teishin Hospital, Osaka, Japan
M. Kaido (Y)
Department of Neurology, Osaka University Medical School,
2-2 Yamadaoka, Suita, Osaka 565, Japan
Tel.: 6-879-3571; Fax: 6-879-3579

chromosome analysis. The results suggest a possible correlation between this mitochondrial DNA abnormality
and Alzheimer-type pathology.
Key words Mitochondrial myopathy, encephalopathy ·
Lactic acidosis and stroke-like episodes (MELAS) ·
Alzheimer disease · Senile plaque · β-protein ·
Mitochondrial DNA

Introduction
Mitochondrial myopathy, encephalopathy, lactic acidosis
and stroke-like episodes (MELAS) was first described by
Palvakis et al. [20] as a distinctive clinical syndrome
among mitochondrial encephalomyopathies. Analysis of
mitochondrial DNA (mtDNA) has proven that the point
mutation in tRNALeu(UUR) is responsible for about 80% of
MELAS cases [5, 6]. Patients with MELAS characteristically present with an abrupt onset of episodic vomiting,
seizures, and recurrent stroke-like events such as hemiparesis, hemianopsia, or cortical blindness before adolescence. Mental regression is not infrequently observed [6],
and psychiatric symptoms are sometimes seen in patients
with MELAS together with or before the stroke-like
episodes [22, 23]. Neuropathological findings so far reported include cortical atrophy with severe loss of neurons, gliosis, spongy degeneration of layers of the cerebral
cortex, calcification in the basal ganglia, multiple foci of
infarction without correlation to vascular supply, and peculiar vascular changes called “mitochondrial angiopathy” [3, 7, 18, 19]. We report here the neuropathological
findings identical to those seen in Alzheimer disease in a
patient with MELAS who presented psychiatric symptoms without stroke-like events.

Case report
A 53-year-old Japanese woman was transferred to a regional hospital because of repetitive vomiting, anuresis, and cloudiness of
consciousness. Prior to this episode, she had shown loss of appetite

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Fig. 1 Family tree. III-1 A short-statured and mentally retarded
22-year-old woman having hearing impairment from age 6 years,
and diabetes mellitus from 18 years. III-3 A short-statured, emaciated, and mentally retarded 10-year-old girl showing diffuse muscular weakness, blepharoptosis, and ataxic gait. She suffered from
stroke-like episodes twice, once at 6 years and once at 9 years of
age (m male, no neuromuscular disease; p probably affected female; P affected female; r+ stillborn; → proband)

and apathy for 6 months. There was no history of stroke or convulsion. Her mother had been short-statured and frail, and her two
daughters suffered from mitochondrial encephalomyopathy (Fig.
1). The three women were diagnosed as having typical MELAS
syndrome with a point mutation in mtDNA (tRNALeu(UUR), nt3243)
by DNA analysis [10].
Physical examination on admission revealed a short stature
with emaciation (height 142 cm, weight 24 kg), hypotension (systolic; 60–90 mm Hg), axillary atrichia, atrophy of mammary glands,
and abdominal bloating with full bladder. Neurologically, she
showed clouding of consciousness (Glasgow coma scale E2V2M4)
and generalized muscle atrophy.
Laboratory examination showed abnormally low levels of
serum sodium (109 mEq/l) and chloride (76 mEq/l). Serum glucose was 159 mg/dl, but calcium was normal. There was no renal
failure or respiratory insufficiency. Other abnormalities included
mild liver dysfunction probably due to hepatitis C, hypolipidemia
(total cholesterol 114 mg/dl, triglyceride 25 mg/dl), elevated C-reactive protein (2.4 mg/dl), borderline anemia, and urinary ketone
bodies. Endocrinologically, thyroid function was normal, but
adrenocorticotrophic hormone and gonadotropin were reduced.
Serum lactate and pyruvate levels were nearly normal, but they

were elevated in cerebrospinal fluid (lactate, 36.1 mg/dl; pyruvate,
1.43 mg/dl). Cranial computed tomography and magnetic resonance imaging showed diffuse cerebral atrophy. Neither low-density areas nor calcification were present in the basal ganglia. An
electroencephalogram showed slow-wave activities, and an electromyogram showed myogenic changes in all extremities.
Muscle biopsy from the biceps brachii muscle disclosed mild
myopathic changes with ragged-red fibers and “strongly succinate
dehydrogenase-reactive blood vessels” (SSV) [8] (Figs. 2 a, 4 a).
On electron microscopic examination, there were large subsarcolemmal aggregates of mitochondria, some of which had paracrystalline inclusions.
Chromosomal analysis showed 46XX, and mtDNA analysis
showed adenine to guanine substitution at nucleotide 3243 in tRNALeu(UUR). The proportion of mutant mtDNA was 82% in the
biopsied muscle, and 10% in lymphocytes [10].
Although her general condition improved after symptomatic
treatment, psychosis developed. She began to shout loudly, complaining of fearful hallucinations, which required treatment with
neuroleptics. Subsequently, she suffered from repetitive urinary
tract infection. Four months later, she developed paralytic ileus
and became markedly emaciated with a body weight of 19 kg.
Though her condition improved for a while, she was found dead at
home. The postmortem examination was performed at an estimated 30 h after death.
Pathological analyses
Routine specimens for light- and electron-microscopic examinations were prepared. In addition, some specimens from the extraocular muscles, frontal cortex, basal ganglia, spinal cord,
choroid plexus, iliopsoas and deltoid muscles were quickly frozen
and later examined with enzyme histochemistry for cytochrome c
oxidase (COX) and succinate dehydrogenase (SDH) [4]. The immunohistochemical study was carried out using formalin-fixed,
paraffin-embedded sections of the middle frontal gyrus and Ammon’s horn. For this purpose, the antibodies against β-protein [21]
(anti-β/A41–16, rabbit polyclonal antiserum, 1 : 100; kindly provided by Dr. Shoichi Ishiura, Institute of Molecular and Cellular
Biology, Tokyo University), tau (monoconal, 1 : 500; Chemicon),
ubiquitin (rabbit polyclonal, 1 : 500; Dakopatts, Denmark), 68kDa
and 200kDa neurofilament (monoclonal, 1 : 200 each; Dakopatts),

Fig. 2 a, b Muscle pathology
of the patient. Biopsy of the biceps brachii muscle revealed
ragged-red fibers on modified
Gomori-trichrome stain (a).
Mosaic pattern deficiency of
cytochrome c coxidase is also
found in autopsied extraocular
muscle (b). Bars = 25 µm

a

b

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Table 1 The distribution of senile plaques and Alzheimer neurofibrillary tangles
Senile plaquesa

a

Diffuse

Primi- Classic
tive

Alzheimer
neurofibrillary
tangles

Cerebral cortex
Frontal cortex
Temporal cortex
Parietal cortex
Occipital cortex

+++
+++
+++
+++

++
+
+
+

+
+
+
–

–
–
–
–

Parahippocampal gyrus

++

++

+

++b

Hippocampus

++

+

+

–

Striatum

+

–

–

–

Basal nucleus
of Meynert

–

–

–

–

Thalamus

+

+

–

–

Cerebellar cortex

+

–

–

–

a The number of senile plaques are assessed as follows:

–, 0; +, 1–7; ++, 8–14; +++, > 15 per mm2 at the microscopic magnification × 200
b About 20 per mm2 of neurofibrillary tangles at the microscopic
magnification × 200

Results
Pathological analyses
General neuropathological findings
b
Fig. 3 a, b Bielschowsky silver staining of the brain. There are numerous senile plaques throughout the layers in the frontal cortex
(a, bar = 300 µm), and many neurofibrillary tangles in the parahippocampal gyrus (b, bar = 50 µm)

α-choline acetyltransferase (monoclonal, 1 : 200; Chemicon), and
acetylcholinesterase (monoclonal, 1 : 150; Chemicon) were used.
A positive immunoperoxidase reaction was visualized by the biotin-strepotavidin method (Histofine, Japan). Formic acid pretreatment was incorporated for the procedure for β-protein [14].
DNA analyses
Distribution of mutant mtDNA(tRNALeu(UUR), nt3243) was investigated with the quickly frozen specimens from the frontal cortex,
putamen, globus pallidus, and dorsal root ganglia. A DNA sample
prepared from each tissue was digested with endonuclease Apa I
and subjected to Southern blot analysis. To estimate the proportion
of mutant mtDNA, the radioactivity of each band was measured.
Mutations on exon 17 of the β-amyloid precursor protein (APP)
gene, known to be responsible for some familial cases of Alzheimer disease [15, 16], and the NADH dehydrogenase subunit 2
(ND2) gene of mtDNA were sequenced to find the substitution on
codon 693, 713 and 717 (APP), and codon 331 (ND2), respectively.

The brain weighed 910 g after fixation. Mild diffuse cerebral atrophy and dilatation of the ventricles were noted.
There were no cystic cavities, spongiform changes, or significant loss of neurons on hematoxylin and eosin staining. Bielschowsky silver stain demonstrated widespread
numerous senile plaques throughout the entire cerebral
cortices (Fig. 3 a). There were numerous Alzheimer neurofibrillary tangles (NFTs) in the parahippocampal gyrus
(Fig. 3 b), but not in other areas. The distribution of senile
plaques and NFTs is shown in Table 1. Granulovacuolar
degeneration was also found in the hippocampus.
Enzyme-histochemical findings
The SDH method demonstrated strong reaction on blood
vessels (SSV) both in muscles and the central nervous
system (Fig. 4). The COX method revealed partial COX
deficiency in the extraocular muscle (Fig. 2 b) and cardiac
muscle, but not in the central nervous system.
Immunohistochemical findings
Senile plaques were positive for β-protein, but negative
for neurofilament, α-choline acetyltransferase, or acetylcholinesterase. There were only a small number of tau-

315
Fig. 4 a–c Strongly succinate
dehydrogenase (SDH)-reactive
blood vessels (SSV). SDH
staining reveals SSV not only
in the skeletal muscle (a), but
also in the extraocular muscle
(b) and globus pallidus (c).
Bars = 50 µm

a

b

c

Table 2 Distribution of mutant mitochondrial DNA (%)

Frontal cortex
Putamen
Globus pallidus
Dorsal root ganglia

89
86
80
53

positive or ubiquitin-positive plaques in the tissues examined.
DNA analyses for mtDNA and the APP gene
The distribution of the mutant mtDNA is shown in Table
2. The percentage of the mutant was highest in the frontal
cortex, where senile plaques were most frequently seen.

316
Fig. 5 a, b Diffuse senile
plaques. In frontal cortex, βprotein deposits are widely
observed on immunostaining
against β-protein (a, bar = 100
µm). Most plaques show simple amyloid deposition without
degenerative neurites on electron microscopy (b, bar =
0.5 µm)

a

b

There was no mutation in the ND2 gene or exon 17 of the
APP gene.

Discussion
We have reported a patient with MELAS as a result of a
typical mutation in mtDNA (tRNALeu(UUR), nt3243). She
did not have cerebral infarction but had numerous senile
plaques in the brain. Clinically, she had suffered from
psychosis instead of stroke-like episodes and probably
had hypothalamo-pituitary insufficiency. These features are
not infrequently encountered in patients with MELAS [11,
22, 23]. The diagnosis was confirmed by biopsied skeletal muscle morphology and mtDNA analysis. Coincidental Down syndrome was ruled out by chromosomal analysis.
There have been over 1000 papers on mitochondrial
encephalomyopathy in the past 30 years. Among them,

about 300 were concerned with MELAS, and 20 autopsy
cases have been investigated pathologically, including the
central nervous system. The neuropathological alterations
of MELAS frequently described are multiple infarct-like
lesions, calcification in the basal ganglia, and “mitochondrial angiopathy” [3, 7, 19]. However, we have not encountered a paper describing the presence of senile plaques
in past autopsy reports on MELAS, chronic progressive
external ophthalmoplegia, Kearns-Sayre syndrome, myoclonic epilepsy with ragged-red fibers, or other types of
mitochondrial encephalomyopathy. Since the majority of
such patients were younger than 40 years old, sufficient
attention may have not been directed to senile changes in
mitochondrial encephalomyopathy. Recently, however,
mitochondrial abnormalities have been pointed out in
some degenerative diseases including Alzheimer and
Parkinson’s diseases [12, 24]. Therefore, it would be appropriate to look for senile changes in elder autopsy cases
of mitochondrial encephalomyopathy in the future.

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In the present case, we found numerous senile plaques
throughout the brain, but this does not necessarily indicate
the presence of Alzheimer disease, because this patient’s
clinical history was not typical of Alzheimer disease.
NFTs were detected only in the parahippocampal gyrus
and neuronal loss was not prominent throughout the brain.
There were some senile plaques of the classic type, but
most were of the primitive/diffuse type. It has been shown
that some non-demented adults have cortical primitive/
diffuse plaques [13, 17]; however, according to the morphometric criteria described by Khachaturian [13], the
number and the distribution of senile plaques in our case
as shown in Table 1 were certainly outside the normal
range, and we have to entertain the possible relationship
between senile plaques and the underlying disease.
Since there have been reports on the mutations on the
APP gene in familial Alzheimer disease [15], we explored
the presence of mutations on codon 693, 713 and 717 of
the APP gene; however, they were all negative. MtDNA
mutations have also been reported in Alzheimer and
Parkinson’s disease [12, 16]. A mild defect in oxidative
phosphorylation has been considered to be responsible for
an increase in the risk for those diseases [9, 12, 16]. Our
patient had a point mutation in mitochondrial tRNALeu(UUR),
but codon 331 of the ND2 gene did not have a mutation.
Blass and associates [1, 2] have proposed a “mitochondrial hypothesis” for pathophysiology of Alzheimer disease. They found abnormalities in three mitochondrial enzymes in Alzheimer brain: pyruvate dehydrogenase, ketoglutarate dehydrogenase complex (KGDHC), and monoamine oxidase. They have postulated that a profound
deficit of KGDHC is likely to lead to impaired metabolism of glutamate and contribute to selective neuronal loss
by the excitotoxic mechanism as well as by direct effects
on energy metabolism through its role in the tricarboxylic
acid cycle. As to the accumulation of β-protein, they have
postulated that the damage to mitochondria in Alzheimer
disease is severe enough to lead to dysregulation of second messengers including cyclic AMP and calcium, causing excess kinase activities, and that abnormal kinase activities may lead to aberrant phosphorylation of APP.
Although the possibility of the coincidental occurrence
of MELAS and Alzheimer pathology cannot be excluded
in our patient, the mitochondrial abnormality thus might
have played some role in the formation of senile plaques,
especially in the deposition of β-protein.
Acknowledgements This work was supported, in part, by a grant
from the Ministry of Health and Welfare, Japan. The authors thank
Ms. C. Kato for her skillful technical assistance. We also thand Dr.
S. Okamoto, Osaka Teishin Hospital, for performing the autopsy.

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