mitochondrial abnormalities in oculopharyngeal muscular dystrophy

A family with oculopharyngeal muscular dystrophy (OPMD) is described. Histological and histochemical studies of muscle biopsy showed nonspecific myopathic changes; no "ragged-red'' fibers were seen. Electron microscopy demonstrated bizarre large mitochondria with abnormal cristae, but no intranuclear inclusion bodies. Our findings are compatible with the possibility that OPMD is a heterogeneous syndrome, and may be a mani- festation of mitochondria1 myopathy. Key words: oculopharyngeal muscular dystrophy mitochondrial myopathy

oculomyopathy muscular dystrophy MUSCLE 81 NERVE 14:947-952 1991

MITOCHONDRIAL ABNORMALITIES IN OCULOPHARYNGEAL MUSCULAR DYSTROPHY

RACHEL PAWNER, MD, ILAN BLATT, MD, MElR MOUALLEM, MD, ElTAN BEN-DAVID, MSc, ZVI FARFEL, MD, and MENACHEM SADEH, MD

Oculopharyngeal muscular dystrophy (OPMD), a rare autosomal dominant genetic disorder, was first described by Taylor in 1915,13 and traced to a common French ancestor who settled in Quebec in the seventeenth ~ e n t u r y . ' ~ It has since been found in various ethnic groups such as the Italian, Spanish, Norwegian, and Japanese. Few cases have been reported among Jews. Victor et al.17 described 10 such patients: 1 sporadic and 9 cases in three generations of a North American family of Eastern European origin. Schotland and Row- land" found 11 cases in five Jewish families.

Late adult onset of ptosis and dysphagia are characteristic, though weakness in facial, mastica- tory, neck, and limb muscles has also been described. The patho enetic basis for the syndrome is not well definedr5 Tome et al. have found intranuclear inclusion bodies and suggested that this is a hallmark of the However, other workers have discovered mitochondrial abnormalities.3,7,1 1 We present here further evidence for

mitochondrial abnormalities not described previ- ously in a family with OPMD.

CASEREPORTS

Case 1. An 8 1-year-old Jewish, non-Ashkenazi man born in Buchara, Uzbekistan was hospitalized because of syncope due to bradycardia caused by propranolol. The patient has had bilateral ptosis for more than 15 years, and for 5 years has com- plained of progressive difficulty in swallowing solid food. Bronchitis was diagnosed because of

From the Department of Internal Medicine E (Drs Pauzner, Mouallem, Farfel and Sadeh), and Department of Neurology (Dr. Blatt), The Chaim Sheba Medical Center, Tel Hashomer and Department of Pathology, Bei- linson Medical Center (Mr. Ben-David), affiliated with the Sackler School of Medicine, Tel Aviv University, Israel.

Address reprint requests to R. Pauzner, MD, Department of Internal Med- icine E, The Chaim Sheba Medical Center, Tel Hashomer 52621, Israel.

Accepted for publication July 18, 1990

CCC 01 48-639)(/91/0100947-06 $04.00 0 1991 John Wiley & Sons, lnc.

FIGURE 1. Case 1 : bilateral ptosis and contraction of the frontalis muscle.

Mitochondria in Oculopharyngeal Muscular Dystrophy MUSCLE & NERVE October 1991 947

FIGURE 2. Irregular patches of absent enzyme product reaction are seen with subsarcolemmal aggregates. NADH-tetrazolium reductase ( x 250).

FIGURE 3. Electron micrograph shows thickened, dense aggregates within the mitochondria and loss of normal mitochondria1 structure (x45,OOO).

recurrent episodes of productive cough upon swallowing. The dysphagia had worsened during the last 2 years with a weight loss of 10 kg. Dys- phonia developed as well.

On physical examination, the patient weighed 52 kg and had bilateral ptosis compensated by contraction of the frontalis muscle and by holding the head backward (Fig. 1). Eye movements were limited and slow in all directions. The pupils were equal and reacted to light and accomodation. There was no eyelid fatigue or evidence of myoto- nia. Speech had a nasal quality, but the palate was symmetric with a central uvula and the gag reflex normal. There was mild proximal weakness of the lower limbs. An apical systolic murmur and a dias- tolic murmur at the left sternal border were heard. The rest of the physical examination was normal.

Biochemical blood studies, including creatinine kinase, yielded normal results. ECG showed sinus bradycardia and right bundle branch block. A 24- hour Holter recording revealed sinus bradycardia, not less than 50 beats/min. Echocardiogram demonstrated mild mitral insufficiency, moderate aor- tic insufficiency, and good left ventricular func- tion. A tensilon test was negative.

Nerve conduction velocity studies yielded normal values as did electromyography of limb muscles, and no myotonic discharges were observed.

A sample of biopsied deltoid muscle was rap-

idly frozen in isopentan cooled in liquid nitrogen. Sections of 10 micrometers were stained with he- matoxylin and eosin, modified Gomori trichrome, Sudan black B, NADH-tetrazolium reductase, succinic dehydrogenase, and ATPase at pH 9.4 and after preincubation at pH 4.6 and 4.25.4 Another portion was fixed in 3% gluteraldehyde in cacody- late buffer treated with osmic acid, embedded in epon and prepared for electron microscopy.

Light microscopy revealed variability in muscle fiber size with no connective tissue, fatty, or in- flammatory infiltration. With the NADH-TR and succinic dehydrogenase reactions, many “moth- eaten” fibers were observed. Areas devoid of oxi- dative enzyme reactions were present in both fiber types. Many fibers showed subsacrolemmal difor- mazan deposition (Fig. 2). However, with the modified Gomori trichrome stain, no ragged red fibers were seen. Small angulated fibers were absent, and there were no vacuoles.

Electron microscopy revealed areas of disinte- gration of sarcomeres and foci of Z-disc stream- ing. Nuclei appeared normal, and no intranuclear filamentous inclusions were found in spite of a careful search in many fibers. Subsacrolemmal mitochondria were increased in number. All the mitochondria had an abnormal appearance- they were large with widened clumped bizarre cristae (Fig. 3).

Recently, because of increasing difficulties in

FIGURE 4. Electron micrograph demonstrates aggregation of multiple dark mitochondria within an atrophied muscle (~9,000).


swallowing, the patient underwent cricopharyn- geal m y ~ t o m y , ~ . ~ which relieved the dysphagia. During the operation, a biopsy from one of the anterior neck muscles was taken and prepared for histochemical and electron microscopical studies as described above. Muscle fibers were small, atro- phic, and rounded, separated by a markedly increased amount of fibrous tissue. With the NADH-TR reaction, the fibers were darkly and ir- regularly stained; no ragged-red fibers were observed with the modified Gomori trichrome. Elec- tron microscopy revealed atrophied fibers with sacrolemmal foldings and a reduced number of myofibrils. Abundant dark bizarre mitochondria were observed between myofibrils (Fig. 4). At a higher magnification, the mitochondria contained dense homogeneous matrix material and convo- luted cristae (Fig. 5). Other fibers possessed ring- like mitochondria enclosing an abundant amount of matrix material with almost no cristae (Fig. 6). No intranuclear inclusion bodies were observable in this biopsy either.

Case 2. A 75-year-old man, first cousin of patient 1, was known to have had bilateral ptosis for more than 10 years and dysphagia for 6 years. His weight was 54 kg. Physical examination revealed findings identical to those found in his cousin, ex- cept that no heart murmurs were found. The patient refused any investigation.

Information about other members of the family is provided in Figure 7 which shows the family pedigree. Thirteen cases in four generations were affected by the disease. Autosomal dominant pat- tern of inheritance is obvious.

DISCUSSION

Oculopharyngeal dystrophy is inherited as an autosomal dominant trait becoming manifest in the fifth or sixth decade mainly by ptosis and dysphagia, with later involvement of all extraocular muscles. ’’ Many patients may develop laryngeal weakness with dysphonia, and in late stages of the disease, weakness and atrophy of other voluntary muscles. Death occurs at an advanced age as a re- sult of starvation or aspiration pneumonia; a few cases of carcinoma of the esophagus and the stom- ach have been reported. l5

The main disease to be considered in the dif- ferential diagnosis is oculocraniosomatic syndrome (OCSS), in which ptosis appears sometimes unilat- erally, but which invariably shows skeletal muscle involvement, sometimes with dental and skeletal abnormalities. Associated distinguishing findings include retinitis pigmentosa, cerebellar ataxia, hearing loss, mental disturbances, endocrine abnormalities, and cardiac involvement with atrio- ventricular block, which occur in OCSS. Its onset is usually before the age of 30, although it may appear later until the age of 60. The syndrome is sporadic, but there are a few familial cases.15 The characteristic histological finding is ragged red fibers. Recently, deletions of mitochondria1 DNA were found in this syndrome. Though severe dysphagia may also occur in OCSS, our family’s age of onset and mode of inheritance fit the diagnosis of OPMD.

The pathological basis of OPMD was, in the past, suspected to be neurogenic due to degenera- tion of vagal, glossopharyngeal, and oculomotor nuclei. Taylor named the disease “progressive va-

FIGURE 5. Higher magnification of a dark subsarcolemmal large mitochondrion shows coiled cristae and dense matrix material (~40,000).

950 Mitochondria in Oculopharyngeal Muscular Dystrophy MUSCLE & NERVE October 1991

FIGURE 6. In this electron micrograph, mitochondria appear rounded or ring-like, encircling fine granular material (~25,000).

gus-glossopharyngeal paralysis with p to~is .” ’~ nal nuclei, and interstitial fibrosis. l 5 On his- Victor et al., who coined the name OPMD, pro- tochemical studies, fibers appeared split, “moth- posed a myopathic basis. Muscle studies by classi- eaten,” and many were small and angulated. cal histological methods showed nonspecific Rimmed vacuoles were also described, consisting changes, such as decreased muscle fiber size, inter- of irregular round or polygonal clear spaces lined

I

2

5 3 ? ? ?

FIGURE 7. Pedigree of the affected family. Ages provided are either at death or at present. p p t o s i s , ?-no known details.


by a baso hilic ring staining red with Gomori's trichrome. '' Ultrastructural studies showed that the rimmed vacuoles contained membranous struc- tures and a few glycogen granules and debris, arising from the breakdown of unidentified muscle components.

Tome et al.14,16 described nuclear inclusions in 33 cases. Under high magnification, these looked like tubular filaments with an external diameter of 8.5 nm, randomly organized or arranged in pali- sades, an appearance confirmed by others. 16- l8

Tome et al. considered this finding to be the hallmark of OPMD.

Mitochondrial abnormalities in OPMD were re orted in 2 patients by Couturier et al.3 Julien et al. reported a case with abnormal mitochondria that contained inclusion bodies composed of con- centric lamellae of short electron-dense linear ele-

1:

ments. Prat et al." reported another case with mitochondrial abnormalities. Abnormal dense irregular metallic inclusions were situated within grossly destroyed mitochondria. In our family, we describe another type of morphological mitochondrial changes.

The specificity of the mitochondrial changes is not certain. It is difficult to assess the role of mitochondrial abnormalities in the pathogenesis of the disease and to determine whether we are dealing with a primary mitochondrial myopathy.

This report, as well as previous reports on mitochondrial abnormalities in OPMD, raise the possibility that OPMD is not a homogeneous disease characterized histologically by intranuclear inclusions, but a more complex syndrome.'7829 Genetic, biochemical, and molecular biology studies are re- quired to classify the disorder more precisely.

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952 Mitochondria in Oculopharyngeal Muscular Dystrophy MUSCLE & NERVE October 1991

mitochondrial abnormalities in oculopharyngeal muscular dystrophy

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