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A CASE OF A P P A R E N T DISSIMILARITY O F MONOZYGOTIC TWINS

BY AUBREY LEWIS, M.D., M.R.C.P.

THE physical characteristics used to determine whether twins are monozygotic have been much discussed ; they represent a selection of manifest normal features considered to be the least influenced by other than hereditary factors. Some, such as eye colour, skin pattern, and skeletal dimensions, are easily determined and therefore most used; others, such as blood group or degree of corneal aatigmatism, require special technique; but all rest on the same statistical basis. It is not on such developmental criteria as the singleness or otherwise of their birth membranes that twins are determined to be monozygotic but according to whether they have certain features that do not otherwise so regularly occur together in sibs. Obviously the number of such characteristics increases as investigation proceeds, but fallacy in selecting the initial determining features will tend to vitiate further work. Among the criteria commonly employed are facial appearance and skeletal structure. In the pair of twins here reported, and dealt with elsewhere from a medical point of view (7), the use of such criteria would have been misleading.

One of the twins showed the features of the hypophyseal disorder, acromegaly; one should rather say, acromegaloidism, since the condition was not progressive or weakening, and occurred in a family prone to lofty stature, if not gigantism. In the other twin no sign of this disorder could be discovered. The disparity between the two is evident in the accompanying photographs and skiagrams (see Plates I-VII) ; it had first been noticed a t puberty, not long after the one who became taller had sustained a cranial injury. Skeletal measurements now show striking differences (Table 11).

Similarity may still be seen in the finger and palm prints (Plates VIII-X), the iris colour and the blood groups, as well as in the accessory bones of the hand. Until puberty the twins had been constantly mistaken for one another. The palm-print formulae* of the twins and their siblings were as shown in Table 111.

The blood groups to which the siblings belonged were:

( ... ... AB \ ... ... AB

... ... AB ... ... AB

... ... A Mrs ... ... ... A Mrs ... ... ... AB

The twins .

* A brief description of the notation employed, together with a report on the finger prints by Dr Percy Stocks, is appended (see Additional Note).

A. LEWIS 69

It 0 0

s E E

L . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . : : 8 : : : : : : : : : : : : . a . . . . . . . . . . . .

CI 0

60 A P P A R E N T DISSIMILARITY O F MONOZYGOTIC T W I N S

Further details as to the history and physical state of the twins are given in a previous paper. The hereditary factors entering into the condition are there also discussed. The significance of these may be partly recognised in the accompanying pedigree with its large number of antecedents and collaterals of unusually tall stature; it may also be noted that the twin of normal height ( 5 ft. 8 in.) has a son who is 5 ft. 11 in. high, at the age of 20.

This rare instance raises several interesting points concerning the diagnosis of mono- zygosity in twins. Stocks(14) came to the conclusion that the best criteria were to be found in finger prints, height and four simple measurements of the hand, and that one might, as an alternative, from the finger prints alone determine whether monozygous or not; he stated in his summary that "a difference in height exceeding the standard deviation of height appropriate to the age of the pair almost certainly excludes monozygotism". He shows in his paper that, although it would be possible to devise a method of diagnosis

Table 111. Palm-print formulae

Mrs

Mrs

Right hand Left hand Right hand Left hand Right hand Left hand Right hand Left hand Right hand Left hand Right hand Left hand Right hand Left hand Right hand Left hand

...

...

...

...

...

...

...

...

...

...

...

...

...* ... ... ...

9 z 5' (5") 4 7 5" 4 3"P 9 x 5' (5") 4 7 5" 4 3"P 1 1 9 7 4 9 ? 5' 3" h 9 ( 8 ) 7 5' 3 ? 5" 5' 3 10 ? 6 3" (4) 9 ? 5" 3" (4) 9 7 5" (5') 4 7 5" 5' 3 " P 8 6 5 ' 9 8 6 ? ? 9 7 5' 3" 9 7 5' (5") 3"

- t - - t - - t - - t - - t - - t - - t - - t - - t - - t - - t - - t - - t" - - p - - t - - t -

0 0 0 0 0 0 A T O 0 L 0 0 0 0 0 0 A r O 0 L

Lr AT 0 0 0 0 A T O 0 0 0 A T 0 0 0 0 0 0 0 0 0 0 0 0 0 Lr A' 0 0 0 0 Ar 0 0 LJO O O O O T O O O O T

0 0 0 O I L 0

0 0 0 0 LIO 0 0 0 0 LIO

based on differences by utilising a large number of measurements without resort to finger prints, this would be so laborious in application as to be of little practical use. von Verschuer(4,15), however, one of the most active of continental workers in the field, has published a long list of the characteristics which he used for determining whether twins were monozygotic. The list consists of the following: blood group, blood factors M and N , colour of iris, hair colour, skin colour, hair form, eyebrows, nose, lips, tongue, ear, cutaneous vessels, position and form of teeth, freckles, finger prints, and finally anthropological measurements such as body weight and height, and the length and breadth of various skeletal structures. Many of these would, however, have been misleading, if applied to the cases here under consideration. It may be reaffirmed that similarity of finger and palm prints are the most trustworthy criteria(10,ll).

Morphological discrepancies between monozygotic twins have been comparatively little regarded. Attention has been paid by various writers (Newman ( b , 9 ) , Bouterwek (2)) to

A. L E W I S 61

the interesting differences between monozygotic twins as regards asymmetry and mirror reversal of the features, but there is very little to be found on the more general skeletal differences ; similarities are of course much emphasised : thus von Verschuer (15) finds body height to be the rinthropometric character least influenced by the environment, with head length a close second in this respect. Isolated reports on teeth(6) are available, and there are several communications about differences found at or soon after birth. In Buschke’s radiographic studies (3) of juvenile twins, he discovered differences as to the order in which centres of ossification appeared in the carpal bones and in the elbows of monozygotic twins, as well as differences as to the stage of skeletal maturity attained by each twin at a given age. There are also a few reports of unlikeness in general structure due to mainly environmental factors, e.g. Siemens’ two instances (13) of monozygotic twins discordant as to the shape and size of their heads (through exogenous oxycephaly), and his case of scoliosis through r i c k e t s ~ . A still more interesting case is that recently reported by Komai and Fukuoka (51 , where a pronounced disparity in height between the monozygotic twins was closely related to diabetes insipidus, which appeared in one of them about the age of six, about the time his growth fell behind that of his twin: the affected boy, now aged 15, has a smaller pituitary fossa than his brother. The instance has this in common with the one here reported, that a difference in stature between monozygotic twins is referable to a non-progressive disorder of the pituitary gland.

For various reasons detailed elsewhere, the affection of the pituitary in the twin may be attributed in part to a cranial injury sustained at the age of 12. But

since so many members of his family were exceptionally tall and since his monozygotic twin brother has a tall son, one must assume potentialities of tallness in him. There are many grounds for supposing that in the normal process of development, chemical influences are efficacious at almost all stages, and that in the more differentiated stages the endocrine glands are the chief of these chemical intermediaries between genetic forces and their realisation in growth. The pituitary seems especially important in this respect. There are certain familial peculiarities of jaw and stature which are almost certainly constitutional evidences of a slight hereditary anomaly of pituitary function. Between these and the severe progressive disease, acromegaly, there is a continuous range, as there is in the other direction between them and the normal types of tallness.

It is unsafe to apply to man the knowledge gained about intensity’of manifestation and the factors that influence it in such creatures as Drosophila. It is also at present impossible to say what are the factow in the environment that commonly bring about morbid changes of function in the anterior part of the pituitary. But it is permissible to conjecture that in such a case as that here reported, and in others in the literature, the inherited deter- minants of stature may not be made manifest unless certain unlikely requirements are met: in this instance, trauma to the endocrine gland which contributes to the regulation of growth. In this connection H. Fisher’s view, quoted by Buschke, is of interest; he thinks that supernumerary bones which appear with advancing years are due to the action

62 A P P A R E N T D I S S I M I L A R I T Y O F MONOZYGOTIC T W I N S

of trauma, or of a chronic stimulus, upon preformed cartilaginous nodes; moreover, he holds that the chronic stimulus in question may go out from the pituitary, as in some cases of acromegaly, to which he adds the comment, “auch damit ist eine Entscheidung uber die Endogenese oder Exogenese nicht moglich ”.

I n Buschke’s general review of the literature bearing on the morphogenesis of the skeleton, the meagreness of our knowledge as to the genetic factors for this norm is so apparent that to attempt more precise conjecture would clearly be unfounded.

SUMMARY A family is reported in which there waa a pair of monozygotic twins, with great disparity

as to skeleton and general appearance, due to acromegaloid changes in one of them. The bearing of this on the diagnosis of monozygosity is emphasised. The role of the pituitary in mediating growth, and the interplay between hereditary and environmental factors in bringing about pituitary anomalies, are discussed briefly.

A D D I T I O N A L N O T E ON T H E P A L M A N D F I N G E R P R I N T S

The palm-pattern formula for each of the siblings was given in Table 111. It has been made according to the method of Harris Wilder (Amer. J . Phys. Anthrop. (1929), 12, 3). The main lines arising from the digital

stated in the formula according to the position of their termination at the mar- gin of the hand. Then, after the hyphen, the main lines of the axial triradii are specified, these being followed after an- other hyphen by the pattern formulation of the palm, which is read clockwise, beginning a t the hypothenar eminence.

The symbols used are: 0 equals open space, L equals loop (Lr or Lu according to direction of open end), T equals tented arch, A equals simple arch-not really a pattern. The inter-spaces are arbitrarily numbered 13, 11, 9, 7, the first corre- sponding to that between the thumb and forefinger. Positions on the palm margin are numbered as in the accom- panying diagram ; position 4 indicates the mid-point between the base of the little finger (position 5) and the proximal ulnar margin of hand (position 3).

I I b triradii near the bases of the fingers are - 4 - - . 9

1

Text fig. 1

A. LEWIS 63

Dr Percy Stocks has kindly examined photos of the finger prints for the twins and their available siblings. The method of appraisal of similarity by a rapid superficial examination is admittedly somewhat subjective, in that some other observers might have scored the series differently. His report, however, emphasises strongly the evidence for a mono- zygotic origin. Using the symbols A for Arch, L for Loop, W for Whorl, and C for Composite, he finds :

T = tall twin 8 a b = &c =d =e =

Left hand I

L L L

L, L, ~ - - L L L L C L

?L L

L,

L L C A

L L W W L L L W

Right hand

W L L L L L W L

?L L W L A L W W

L I W

W

?$ L

W

L L L W

His comments are as follows: “Using the criterion of ‘similarity’ as defined in my paper, ‘A biometric investigation

of twins and their brothers and sisters’, Part I (Ann. Eugen. (1930), 4, 82), I find on comparing the 8 sets of prints the following values of a (a = number out of the ten possible sets of corresponding fingers of the same sided hands of the pair which presented ‘similar’ patterns) :

T x a S x a T x b S x b T x c 8 x c T x d 8 x d T x e S x e T x f 8 X f

a=4 u = 4 u=5 a=4 u = 5 or 61 a=5 or 0? u = 5 a=4 a=6 a=6 u = 4 u = 3

The above result, judging from Fig. 7 (Ann. Eugen. (1933), 5 , 34, and Table LXXXII, p. 38), makes it highly probable that the pair is monbzygotic. I have never met with a value a = 8 for a pair of twins who would not on other grounds have been classed as ‘ identical ’ .”

64 A P P A R E N T D I S S I M I L A R I T Y O F MONOZYGOTIC T W I N S

REFERENCES

(1) BORCHARDT, L. (1931). Z . ges. Anat. 2. 2. KonstLehre, 10,123 (quoted in Fortschr. Neurol. Psychial. 1933). (2) BOUTERWEK, H. (1934). “ Asymmetrien und Polaritat bei erbgleichen Zwillingen.” Arch. Rms.- u. GesBiol.

(3) BUSCHKE, F. ( 1934). Rontgenologische Skelettstudien an menschlichen Zm’llingen und Mehrlingen. Leipzig :

(4) DIEHL, K. und VON VERSCHUER, 0. (1933). Zm’llingstuberkulose. Jena: Fischer. (5) KOMAI, T. and FUICUOKA, G. (1934). “Post-natal growth disparity in monozygotic twins.” J. Hered.

(6) KORKHAUS, G. (1930). “Anthropologic and odontologic studies of twins.” Zn,t. J. Orthod. 10, 640. ( 7 ) LEWIS, A. J. (1934). “Acromegaly in one of uniovular twins.” J. Neurol. and Psychopath. 16, 1. ( 8 ) NEWMAN, H. H. (1930). “Finger prints of twins.” J. Genet. 23, 415. (9) NEWMAN, H. H. (1931). “Palm-print patterns in twins.” J. Hered. 22, 41.

28, Heft 3, p. 241.

Thieme.

25, No. 10.

(10) REICHLE, H. S. (1934). “Diagnosis of monozygotic twinning.” J. Hered. 26, i. (11) RIFE, D. C. (1933). “Genetic studies of monozygotic twins.” J. Hered. 24, ix, x. (12) SIEMENS, H. W. (1927). “Diagnosis of identity in twins.” J. Hered. 18, v, 207. (13) SIEMENS, H. W. (1924). Die Zwillingsputhobgie. Berlin: Springer. (14) STOCKS, P. (1930). “Biometric investigation of twins.” Ann. Eugen. 4, 49. (15) VON VERSCHUER, 0. (1931). “Ergebnisse der Zwillingsforschung.” Anthrop. Anz. 6, 1. (16) WEITZ, W. (1925). “Studien an eineiigen Zwillingen.” 2. klin. Med. 101, 115.

EXPLANATION OF PLATES I TO X PLATE I

Fig. 1. The twins a t the present time. Fig. 2. The twins a t the age of 15.

PLATES I I TO V

Skiagrams of the skulls of the twins, taken under identical conditions. Observe the disparity in the bones of the skull due to their enlargement in one of the twins, affecting especially the superciliary ridges, the air sinuses, the cheek bones and the mandible.

PLATES V I AND VI I

Skiagrams of the hands of the twins, taken under identical conditions. Observe the disparity due to enlarge- ment of the bones in the affected twin, with broadening and thickening of terminal phalanges and irregular porosis and outgrowths. I n both there is an accessory ossicle at the metacarpo-phalangeal joint of the thumb.

PLATES Vlll TO X

Finger prints of the twins. Palm prints of the twins.

Annals oj’ Eugenics, Vol. VI I , Part I A. Lewis: A case of apparent dissimilarity of monozygotic twins

Plate I

Fig. 2

Fig. 1

Annals of Eugenics, Vol. VII, Part I A. Lewis: A cuse of upparetit diusimilarity of moxozygotic 1uIzt~s

s

Plate I1

4

..

Ann,als of Eugenics, Vol. VII, Part I A. Lewis: A case of apparent dissimilarity of monozygctic twirls

Plate I11

Annals of Eugenics, Vol. VII, Part I A. Lewis: A case of apparent dissimilarity of monozygotic twins

Plate IV

Annals of Eu.genics, Vol. VTI, Part I A. Lewis: A case of apparent dissimilarity of monozygotic twins

Plate V

Annals of Eugenics, Vol VlI, Part I A. Lewis: A case oj' apparent dissimilarity of monozygotic tm'ns

Plate VI

L

Plate VII

Annals of Eugenics, Vol. VII, Part I A. Lewis: A m e of apparent dissimilarity of monozygotic twins

Plate VIII

Left

Annals of Eugenia, Vol. VII, Part I A. Lewis: A caee of appard di8aimilarity of manozygotic twins

Plate IX

Annals of Eugenka, Vol. VII, Part I A. L e d : A case of appard dis~milarity of lnonozygotic twine

Plate X