Journal of the neurological Sciences, 1975, 26:361-375 ~(') Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands

361

Monozygous Twins Discordant for Multiple Sclerosis Report of One Pair and Discussion of Possible Causes of Multiple Sclerosis C. GARDNER-THORPE* AND J. B. FOSTER

Regional Neurological Centre, Newcastle University Hospital Group, Newcastle upon Tyne (Great Britain) (Received 3 April, 1975)

INTRODUCTION

The purpose of this study was to determine whether one pair of twins, discordant for multiple sclerosis (MS), were monozygous and to determine which differences in their life histories could be related to the development of the MS. Monozygous (identical) twins possess identical genes. When only 1 identical twin develops an illness, a study of the differences in his life history from that of his brother may lead to the identification of significant aetiological factors. It may be presumed on theoretical grounds that both twins would develop the illness if both were exposed to the appropriate environmental factors since genetic influences are likely to operate equally in both. Three criteria must be fulfilled (Pembrey 1972) to prove discordance in monozygous twins: (1) although it can never be proved with certainty that the twins are monozygous, the probability must be very high; (2) it must be proved that 1 twin has contracted the illness; (3) it must be shown with a high degree of probability that the other twin is free from the illness and that the twins are therefore discordant with respect to that particular illness.

Evidence of monozygosity in previous studies Evidence of monozygosity requires a study of physical characteristics, blood groups and fingerprints. The earlier reports of twins discordant for MS (Matzdorff 1937; Voss 1937) did not include sufficient detail to provide the proof of monozygosity which is required today. Pratt (1951) mentioned 2 pairs of twins discordant for MS. Thums (1951) described 12 pairs and brought up to date his earlier report * Present address: Department of Neurology, Royal Devon and Exeter Hospital (Wonford), Exeter EX2 5DW, Devon, Great Britain.

362

('. ( I A R D N E R - T H O R P E , J. B. FOSTER

(Thums 1936). Bammer, Schaltenbrand and Solcher (t960) described 5 pairs but the diagnosis of MS in 1 twin was uncertain. MacKay and Myriamhopoulos (1966) followed up an earlier report (MacKay and Myrianthopoulos 1958) of 30 pairs of twins discordant for MS: they also studied concordant pairs but neither concordance nor discordance was related to birth order, occupation, socio-economic status, nationality, religious affiliation, dietary habits or daily activities. Schapira, Poskanzer and Miller (1963) studied 3 pairs of monozygous twins discordant for MS but attempts to trace these patients have not been successful. Holmes. Stubbs and Larsen (1967) described a pair of monozygous (MZ) twins apparently discordant for MS: however, 1 twin suffered from systemic lupus erythematosus. Other workers (Cendrowski 1968) who have described cases of MZ twins include Koch, Stazio and co-workers, and Markov and Leonovich but their publications were not obtainable. Evidence of dis~:ordance The evidence of discordance depends in part upon the length of time during which the twins have been observed. This is best illustrated by examining the reports of monozygous twins concordant for MS. The time intervals between the development of the first symptom or sign of MS in each pair of twins has varied in previous reports, ranging from 2 years (Isenschmid and Otloz 1939) to 24 years (Curtius and Speer 1937): in other studies (Williams 1946; Reese 1950; Thums 195t; Bammer et al. 1960; MacKay and Myrianthopoulos 1966) the interval either has been within this range or has not been stated. Some of the reports also fail to provide adequate proof of monozygosity but nevertheless the interval of 24 years between the onset of MS in twins cannot be disregarded and it indicates that prolonged follow-up is needed to prove discordance. The follow-up periods in the twin pairs reported by Bammer et al. (1960) ranged from 5 to 25 years. Cause of MS The evidence for the various theories which have been advanced has been discussed by McAlpine, Lumsden and Acheson (1972). These theories will not be discussed in detail again here. METHODS

Detailed medical and social histories of the twins, their mother and several other members of the family were obtained. Previous hospital records and National Health Service Executive Council records were examined. In order to confirm that the twins were identical (monozygous), studies of blood groups, isoenzymes, secretor status, HL-A haplotype and fingerprints were made. Various other clinical, haematological, biochemical and microbiological investigations were also undertaken. RESULTS

Evidence of monozyyosity The facial and bodily appearances of the twins- including ear-lobes, palms, teeth,

363

MONOZYGOUS TWINS DISCORDANT FOR MULTIPLE SCLEROSIS

u v u l a a n d p o l y p o i d w a r t s o n t h e c h e s t - - w e r e s i m i l a r . T a b l e I lists d e t a i l s o f m o n o g e n i c t r a i t s in t h e t w i n s a n d t h e i r m o t h e r . T a b l e 2 lists d e t a i l s o f t h e f i n g e r p r i n t s t u d i e s o f t h e t w i n s a n d t h e i r m o t h e r . T h e t w i n s ' f a t h e r is d e a d a n d it w a s n o t p o s s i b l e to determine

for w h i c h

was a "random

traits he was

heterozygous

but

it w a s

assumed

that

he

E n g l i s h m a n " . O n t h i s b a s i s it w a s c a l c u l a t e d t h a t t h e p r o b a b i l i t y

o f m o n o z y g o s i t y w a s 0.9999991

i.e. t h e r e w e r e n o m o r e t h a n 9 c h a n c e s in a m i l l i o n

that the twins were not identical. Phenylthiourea

taste thresholds were determined (Clarke

1964). T h e u n a f f e c t e d

TABLE1 M O N O G E N I C TRAITS D E T E R M I N E D IN T W I N S AND T H E I R MOTHER

One twin had MS and the other twin was normal. Dermatoglyphic studies are listed in Table 2. Marker ~

Twins

Mother

Sex Rhesus MNS Duffy ABH secretor Haptoglobin Acid phosphatase PGD Phosphoglucomatase Adenosine deaminase GPT HL-A

M rr MSM, Fy~'Fyb sese 2 -1 B A 2 1 I 2 1 HL-A 9, R" (W5)/HL-A 11

F R 2r M~M~ FybFy b Sese 2 2 BA AB 2 2 1 1 HL-A 9, R" (W5)/Da22 (W29), HL-A 12

All samples were 0, G m + 1 - 2 + 10, Gc 2 - 1, kk, AK I, Inv - 1, transferrin C, secretor of Lewis, Pi M

TABLE 2 D E R M A T O G L Y P H I C STUDIES U N D E R T A K E N IN T W I N S AND T H E I R MOTHER

One twin (affected twin) had MS and the other twin was normal. Qualitative assessment showed marked similarities in the twins but the mother was different. Normal twin

Ajfected twin

Mother

243 74 52 73 169

264 72 57 65 179

267 60 38 55 110

ATD angles ( ) right left

40 41

42 37

27 30

Loops hypothenar region 3rd interdigital region

+

+

+

Ridge count fingers total Palm A B B-C C D A D

Key: + = present, - = absent.

364

( . GARDNER-THORPE, J. B. FOSTER

t w i n ( t h r e s h o l d 7) a n d t h e m o t h e r ( t h r e s h o l d 12) w e r e " t a s t e r s " w h e r e a s the a f f e c t e d t w i n ( t h r e s h o l d 2) w a s n o t a " t a s t e r " . T h e f a i l u r e o f t a s t e in t h e a f f e c t e d t w i n w a s a l m o s t c e r t a i n l y a c c o u n t e d for b y a m o d e r a t e d i s t u r b a n c e o f all t a s t e s e n s a t i o n s i n c e h e w a s u n a b l e to t a s t e q u i n i n e a n d c i t r i c a c i d o n a n y a r e a o f t h e t o n g u e a n d t h e e l e c t r i c a l t a s t e t h r e s h o l d w a s g r e a t e r t h a n 440 p A . H o w e v e r , h e c o u l d d i s t i n g u i s h t h e t a s t e s o f s u g a r a n d salt a n d t h e s m e l l o f p e p p e r m i n t oil, c a m p h o r a t e d oil, oil o f c l o v e s a n d a s a f o e t i d a .

Eridence of multiple sclerosis in the affected twin MN (N20648), a 19-year-old manual worker, was first seen at Newcastle General Hospital m 1966. In June 1966 he noticed stiffness of one leg and precipitancy of micturition but these symptoms resolved spontaneously. In August he noticed blurring of vision and pain in the left eye. The corrected visual acuity in the left eye was found to be 2 60. A large central scotoma was demonstrated with a 15-ram white object and the pupillary response to direct light was impaired. The visual acuity spontaneously improved to 6/24 during the following 18 days. The tone in the lower limbs was found to be increased, the tendon reflexes were brisk and the plantar responses were extensor. Mild incoordination was found in the upper limbs. In May 1967 impairment of vision in the right eye and weakness of both lower limbs developed: a wheelchair was provided. Therapy with adrenocorticotrophic hormone (ACTH) was not followed by significant improvement in the symptoms or signs. A depressive illness was treated with nortryptilene. The vision in the right eye continued to deteriorate and in March 1968 the visual acuity was found to be less than 6/60. The lower limbs had become weak and urgency of mieturition had developed. A second episode of retrobulbar neuritis occurred in the left eye in 1968. By 1969, bilateral optic atrophy had developed. Coarse tremor was seen in both hands and position sense in the right hand was impaired. A slight improvement occurred after another course of ACTH therapy. In July the right upper limb became weak and numbness appeared on the right hand side of the face, neck and upper chest, later to resolve spontaneously. In October the stance had become very unsteady and a coarse tremor of the head and neck developed. Six episodes of spasm of the left side of the face, each episode lasting for a period of less than 24 hr, occurred and responded poorly to therapy with perphenazine and ACTH. The patient was again admitted to hospital. On admission to hospital in October 1969 the visual acuity remained less than 6/60: bilateral central scotomata, optic atrophy and impaired pupillary responses to light were found. Conjugate gaze to the right was impaired and light touch was not appreciated in the left trigeminal area. A rhythmical tremor of the head and neck was seen. Gross tremor and incoordination were present in the right upper limb on action but not at rest. In the lower limbs the tone and lendon reflexes were increased: clonus was found at the ankles and both plantar responses were extensor. Appreciation of pinprick and temperature was impaired in a stocking distribution below the right knee but appreciation of pinprick was accentuated in the right thigh and below both knees. Appreciation of the position of the toes was impaired but vibration was felt normally in the feet. Haematological. biochemical and serological tests did not reveal any significant abnormality and the elecu'oencephatogram was mildly abnormal excess theta activity was present in all areas. X-rays of the skull and chest were normal. Stereotactic cryocoagulation of the ventrolateral nucleus of the left thalamus was performed (Professor J. Hankinson) and the tremor was abolished completely. The air encephalogram performed before the operation was normal. The patient was seen at intervals after discharge from hospital. The tremor of the head, neck and right upper limb resolved only partially but was no longer troublesome. The function of the bladder had become automatic in May 1971 and micturition was precipitant. An episode of numbness of the right upper and the lower limbs lasted for approximately 2 weeks in April t972. In June 1972 numbness of the left side of the face and of the left upper and lower limbs developed suddenly and was associated with dribbling of saliva from the left side of the mouth, somnolence and stertorous respiration. The patient was admitted to Newcastle General Hospital again and the symptoms resolved within 24 hr of the onset and without treatment. Apart from the dribbling of saliva, which was not associated with obvious facial weakness, the physical signs were unchanged and the blood pressure was 130/70 mm Hg. Lumbar puncture was performed: the cerebrospinal fluid (CSF) contained several lymphocytes and polymorphonuclear leucocytes/mm3, 18 mg protein/100 ml (of which 160,0 was ),-globulin) and 68 mg sugar/100 ml; the Reiter's Protein Complement Fixation

MONOZYGOUS TWINS DISCORDANT FOR MULTIPLE SCLEROSIS

365

Test and the Venereal Disease Reference Laboratory Test (V.D.R.L test) were both negative. The patient was discharged home. T h r o u g h o u t his illhess, the patient has lived at home and managed to perform everyday activities with help from his mother. During the 7 years since the onset of his illness deterioration has occurred and he is at present (1974) unsteady and almost blind: he feeds himself and visits the lavatory alone but requires help in most other activities.

Lack of evidence of multiple sclerosis in the normal twin Evidence of multiple sclerosis was not found in G N (N47983), the normal twin. Several interviews and a complete clinical examination have failed to reveal any abnormal symptoms or physical signs.

Life histories of the twins The twins lived together in the same house on an estate in one of the poorer districts of Tyneside for the first 19 years of their lives: the normal twin then married and moved to a house situated approximately l mile away. The twins were both active, outgoing boys who attended the same classes in the same 3 schools. The normal twin was the "dominant" person, the more "easy-going" of the two and the one who had the most stamina; the affected twin was the more "highly-strung". The twins spent most of their holidays camping. Both swam but the affected twin was the less able since he had difficulty in moving his legs properly: he also had difficulty in turning when running but it is not clear why this was so. The twins both smoked cigarettes from the age of 10 years: the normal twin smoked approximately 4 cigarettes per day and the affected twin always rather more. At the age of 9 years the affected twin fell into a "workman's lavatory" on a golf course and was "covered from head to foot" but he did not suffer any obvious physical injury. The twins left school at the age of 15 years; the affected twin left three m o n t h s after the normal twin. The affected twin was employed in a bedspring factory and then in a wooden box factory: the normal twin worked for a bedding firm, in a die-casting factory and on several building sites. Consanguinity was not known in the family. Neither twin has knowingly been in contact with any other person with MS. Neither any member of the twins' family nor any member of the family of the normal twin's wife is known either to have or to have had MS.

Birth The pregnancy and labour were normal. The affected twin was born 20 min after the normal twin and was lighter in weight (5 lb 10 oz) than the normal twin (8 lb). The affected twin was "fastened at the throat" and "tubes were introduced into the mouth". Manual removal of the placenta was performed. The condition of the twins evidently caused some alarm since arrangements were made for the christening to take place in the house.

Injection At the age of 5 weeks the affected twin developed pneumonia which was treated with a sulphonamide drug; anuria occurred and was treated in hospital. At the age of 6 years he underwent dental treatment and developed enlargement of the cervical lymph glands and fever. Gastritis and otitis media occurred at 7 years of age, mesenteric adenitis at 8 years, subacute .appendicitis at 9 years, m u m p s parotitis at 10 years, molluscum contagiosum at 11 years and acne vulgaris at 18 years of age. The normal twin developed epistaxis at the age of 3 years, impetigo at 4 years, bronchitis at 6 years, rheumatic fever with involvement of the heart and joints at 7 years, ~mild rheumatism ~" at 10 years, a septic finger and tenderness of the neck muscles at 13 years and paronychia at 14 years of age. Septic spots were treated with penicillin at the age of 17 years. Both twins had infantile diarrhoea. Several upper respiratory tract infections occurred at the age of 2 years the affected twin had fewer than the normal twin. Pertussis occurred at 4 years of age, following which the affected twin developed acute otitis media and bronchopneumonia. At 5 years of age and at the same time both twins developed measles; although the severity of the symptoms was slightly greater in the normal twin, significant complications did not develop in either. Several episodes of tonsillitis occurred at 6 years and varicella occurred at 6 or 7 years of age. Both developed a wry neck within 1 week of each other at approximately 7 years of age. Epidemics of influenza and measles occurred at school.

366

C. GARDNER-THORPE, J. B. FOSTER

A history of other childhood illnesses -including scarlatina, infectious mononucleosis, tuberculosis. acute nephritis and meningitis was not obtained in either twin Tral~ma

Both twins injured various limbs during childhood. The affected twin injured a leg at the age of 9 years, a finger at 11 years, a knee at 16 years, an ankle at 17 years a n d several ribs at 18 years of age. The afl~cted twin also bled profusely when cut. The normal twin injured an ankle both at 5 and at 15 years of age, a testis at 7 >'em~ and a foot at 14 years. Neither twin underwent tonsillectomy or any other surgical operation.

Allergy The normal twin had urticaria. Other differences in allergic response were not found. Neither twin had a history of hay fever, asthma, angioneurotic oedema, food allergy, contact dermatitis or any other form of eczema. Drug reactions have not occurred in either twin and neither has received a blood transiusion. Immunization Records of the immunizations administered at school, including batch numbers of the vaccines, have been destroyed. Whilst at school each twin received 2 injections to protect against poliomyelitis. The affected twin developed an eruption at the site of the injection whereas the normal twin did not develop any eruption. A tuberculin skin test performed in the affected twin at the age of 8 years was negative. Mantoux testing was performed at school at the age of 13 years; the affected twin developed a skin reaction but a reaction did not develop in the normal twin. B C G immunization was undertaken only in the normal twin. The affected twin received 2 injections to protect against tetanus, the first in February t966 and the second approximately I m o n t h later.

TABLE 3 tIAEMATOLOGICAL tNVESI'IGATIONS U N D E R J A K E N IN MONOZY(}OUS I W I N S

One twin (affected twin) had MS and the other twin was normal.

Hb RBC PCV MCV MCHb MCHbC WBC Differential WBC count neutrophils lymphocytes monocytes eosinophils Platelets ESR (Westergren) Blood film Serum B12 Serum folate Serum iron Serum iron-binding capacity

Unit.~

Normal range

Normal twin

,4UPcted twin

g/t00 ml 106imm ~ '!,, 123 ~Lg ",, x 103;mm 3

13.5 18.0 4.5 6.5 40- 54 76-d00 27 32 31 37 4 10

14.4 476 40.5 85 30,4 35.7 8.9

13.7 4,41 3~.2 88 31.2 350 8.1

40 75 20 4 5 2 -10 1 6 150--400 0 10

72 26

?2 23

l 1

a I

320 3 normal 278 7.l 110

242 " normal 340 3.0 76

324

456

x

~:,, of total white count '~; of total white count °/oof total white count !!~, of total white count x 103/ram 3 mm/'hr pg/ml ng/ml ~g/100 ml

> 150 > 3.0 65 150

F~g/1O0 ml

250-400

TABLE 4

367

SOME OF THE BIOCHEMICAL INVESTIGATIONS UNDERTAKEN ON SAMPLES OF SERUM (PLASMA OR URINE WHERE SPECIFIED) FROM MONOZYGOUS TWINS

One twin (affected twin) had MS and the other twin was normal. Units

Urea mg/100 ml plasma Sodium mequiv./1 plasma Potassium mequiv./1 plasma Chloride mequiv./l plasma Bicarbonate mequiv./l plasma Calcium total mg/100 ml Calcium diffusible rag/100 ml Phosphate mg phosph./100 ml Creatinine mg/100 ml Bilirubin mg/100 ml Zinc tubidity flocculation units Thymol tubidity flocculation units Aspartate aminotransferase Rr/units/ml Alanine aminotransferase R v units/ml Lactic dehydrogenase mU/ml Alkaline phosphatase KA units/100 ml Acid phosphatase KA units (formalin stable)/100 ml Albumin g/100 ml Globulin g/lO0 ml Uric acid" mg/100 ml ChotesteroP mg/100 ml Triglycerides" mg/100 ml fi- Lipoproteins" mm Vanillvl mandelic mg excreted in urine acid per 24 hr period 5-Hydroxyindole acetic acid per 24 hr period

Normal range

Normal twin

Affected twin

15-40 135 150 3.6 5.3 95 105 22 32 %11 3.5~4.5 2-4 0.6 1.4 0.14).8