26 Med Genet 1993; 30: 296-299

Polydactyly: a study of a five generation Indianfamily

Uppala Radhakrishna, Asha S Multani, Jitendra V Solanki, Vinod C Shah,Niloufer J Chinoy

AbstractPreaxial polydactyly was observed in upto five generations of an Indian familyliving in a village in the Rajkot district(Gujarat). Among the 71 affected mem-bers, 45 were males and 26 were females.All these affected members showedpreaxial polydactyly manifesting as awell formed, articulated extra digit of thehand or foot. Twenty other cases were

also identified with polydactyly involv-ing triphalangeal digits replacing thethumbs or duplication of the big toe(s).To the best of our knowledge, the presentfamily is the largest in which severalmembers have preaxial polydactyly ofdifferent types. No other abnormalitieswere apparent. The present studystrongly suggests that preaxial polydac-tyly with a well formed extra digit,

Biotechnology,National DairyDevelopment Board,Anand 388 001, India.U Radhakrishna

Department ofZoology, School ofSciences, GujaratUniversity,Ahmedabad 380 009,India.A S MultaniN J Chinoy

Department ofAnimal Genetics andBreeding, VeterinaryCollege, Anand 388001, India.J V Solanki

MS University,Baroda 390 002, India.V C Shah

Correspondence toDr Radhakrishna.

Received 29 April 1992.Revised version accepted2 September 1992.

* 0 Polydactylyo O Bilateral triphalangeal thumb.* 0 Bilateral triphalangeal thumb with

duplication of big toe

Figure I Pedigree of the family.

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Polydactyly: a study of a five generation Indian family

triphalangeal thumbs, and duplication of same autosomal dominant gene. It isthe big toe can be manifestations of the likely that other factors are modifying

the expression of this gene.(J Med Genet 1993;30:296-9)

Table 1 Details of affected subjects.No Pedigree No RH LH RF LF

1 I1l2 II*13 II-34 II-55 II-76 II97 II-138 II-159 II1910 III-311 III-512 III1913 III-1414 III-1715 1111916 III-2017 III2118 III-2219 111-2620 III-2821 111-3522 III-3723 III-3924 III-4125 III-4526 III-4727 III-4928 III-5329 III5730 III-5931 III7032 III-7233 III-7434 III-7635 IV-836 IV 1037 IV-1238 IV-1339 IV-1540 IV-2941 IV-3142 IV-3243 IV-3344 IV-3545 IV-5446 IV-5547 IV-5648 IV-5749 IV-5950 IV-6051 IV-6352 IV-6453 IV-6754 IV-6855 IV-7056 IV-7157 IV-7258 IV-8059 IV-8260 IV-8361 IV-8562 IV-8763 IV-8964 IV-10365 IVi10566 IV-10667 IV-10868 IV11069 IVl ll70 IV-11271 IV 11472 IV 11673 IV-11874 IV-12075 IV-12176 IV- 12477 IV-12678 V279 V580 Vll81 V-1282 V-1583 V 1984 V 2085 V-2186 V-2287 V-2388 V-2789 V-2990 V 3091 V32

RH =right hand,foot, TT= bilaterduplication of big

6656656666665566665566655566666666665656666566656656666666566666566666665666666667

6 56 55 56 56 55 56 56 56 66 56 56 55 55 56 56 56 66 55 55 56 55 56 55 55 55 56 56 55 56 56 66 66 56 56 57 55 56 55 56 56 56 56 55 56 56 56 55 56 56 55 56 66 56 56 56 56 56 55 57 66 56 55 56 55 56 56 56 56 56 56 56 55 56 56 56 56 56 56 57 56 65 5

5555555565565555655555555555556655S55555555555555555SS55S5565555S555555555

Remarks This paper reports on the largest knownIndian family with preaxial polydactyly con-sisting of a well formed extra digit, a triphalan-

TT geal digit in place of the thumb, duplication ofthe big toe, or hexadactyly, representing a high

TT degree of genetic variability. All affected sub-jects are otherwise normal in all respects.

Family reportTT The family studied were inhabitants of a vil-

lage in the Rajkot district of Gujarat. Among265 subjects in five generations of the pedigree(fig 1), there were 45 affected males and 26

TT affected females who had polydactyly withvariable expression (table 1). Figs 2 to 8 show

TTTT & DBTT

TT

''.'!t pt 5

*_ ::

f:5 ::@ *_.t, C . .. ' . ,, .,. _ ..... i .. *., .. >AtWS . _. ! - : qt:. '., !t, t

is {

',' \.'t

TT

TT

TTFigure 2 III39: bilateral fully developed extra fingeron both hands.

TT & DB

TT

TT & DB

Figure 3 III 57: six fingers on the left hand andfivefingers with triphalangeal thumb on the right hand.

TT & DB

5 5 5 5 TT/6 5 5 5 TT6 6 5 55 5 5 5 TT & DB5 5 5 5 TT6 6 5 56 6 5 56 6 5 5

LH=left hand, RF=right foot, LF=leftral triphalangeal thumbs, DB= unilateral Figure 4 III-59: fully developed extra fingers on thetoe (either side). left and right hands.

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Radhakrishna, Multani, Solanki, Shah, Chinoy

Figure 5 IV 83: bilateral polydactyly with sevenfingers on the right hand and six fingers on the left hand.

I

Figure 6 V5: six fingers on both hands with unilateralduplication of the big toe.

Figure 7 V 20: bilateral triphalangeal thumbs.

Figure 8 V 21: polydactyly with six fingers on theright hand and triphalangeal thumb on the left hand.

the various types of polydactyly in differentsubjects. Of the 71 members with polydactyly,five were symmetrically affected in both handsand feet, whereas 56 subjects had six digitsbilaterally on their hands only. The rest of theaffected subjects (n= 10) showed asymmetry inthe number of digits in their hands or feet orboth. In addition to those with a well de-veloped extra digit, 20 other subjects had bila-teral triphalangeal thumbs or unilateral dupli-cation of the big toes or both, indicating a highdegree of phenotypic variation.

Marriages between affected and normal sub-jects produced affected and normal progeny ina 1:1 ratio. This clearly suggests that thepolydactyly is caused by an autosomal domin-ant gene (table 2). Further, distribution ofpolydactyly in the two sexes clearly indicatesthat the expression of the trait is in no wayinfluenced by or linked to the sex of the subject(table 3). Male to male transmission wasobserved in several instances.The majority of the family members were

agricultural labourers but this anomaly doesnot interfere with their work. According to theinformation available and our observations,there were no other malformations, parentalconsanguinity, or reduction in reproductivefitness in the family.The present data support autosomal domin-

ant inheritance with variable expression.

DiscussionThe incidence of polydactyly in the generalpopulation shows quite wide variation amongvarious racial groups ranging from 0 37 to 1 2in 1000 live births.lA The incidence in em-bryos studied through induced abortions inJapan was found to be 0 35%.5 Similar infor-mation is not available for the Indian popula-tion.

Published reports have suggested thatpreaxial polydactyly involving duplication ofthe thumbs/big toes, triphalangeal thumbs/duplication of the big toes, and polydactyly ofan index finger are three different types ofautosomal dominant preaxial polydactyly.However, all three phenotypes are present inthe family reported here. In the family understudy, parents with a triphalangeal thumb (fig7) and duplication of a big toe did not produceoffspring with a fully developed extra finger ortoe. They produced the same type or normaloffspring. However, the parents with preaxial

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Polydactyly: a study of a five generation Indian family

Table 2 Distribution of preaxial polydactyly in offspring from marriages in fourgenerations.

OffspringNo of Calculated

Generation Parents marriages Affected Normal x2 value

IAffected x normal 1 8 5 0-6923(6-5) (6-5)

II Affected x normal 8 25 26 0.0196(25-5) (25-5)

III Affected x normal 16 43 41 0-0476(42-0) (42-0)

IV Affected x normal 15 14 22 0.4444(18-0) (18-0)

Figures in parentheses indicate expected numbers in each group.All calculated X' values were statistically non-significant (p <005).

Table 3 Distribution of preaxial polydactyly in the twosexes.

SexCalculated

Generations Male Female x2 value

II 5 3 0-50III 14 1 1 0-36IV 27 16 2-8139V 7 7 0.0000

All calculated X2 values are statistically non-significant (p < 0-05).

polydactyly with fully developed triphalangeal

digits in addition to the thumb produced chil-

dren with a similar type and/or triphalangeal

thumb and duplication of the big toe polydac-

tyly, perhaps suggesting a degree of genetic

anticipation.

Graham et a!' reported absence of the thenar

intrinsic muscles in four unrelated families

with preaxial thumb polydactyly, which was

associated with inability to flex the thumb

across the palm. However, such observations

were not made in the present family, since the

extra digit was functional and flexed like a

normal finger.Occurrence of preaxial polydactyly of a well

formed extra digit, triphalangeal thumbs, and

duplication of the big toe in the same pedigree

299

indicates a common genetic basis responsiblefor all the varieties. The asymmetry or varia-tion in expression may be the result of involve-ment of modifying genes, polygenes, or someunrecognised effect on the developmental pro-cess. The data presented in table 2 clearlyindicate that the mode of inheritance of poly-dactyly in the present study is autosomal dom-inant.The distribution of polydactyly in the two

sexes is presented in table 3. These findingsindicate an even distribution of polydactyly inboth sexes. The number of affected males wasfound to be higher than affected females indifferent generations, but on statistical analysisthis was found to be non-significant. Further-more, the pedigree clearly indicates that thereis equal transmission of the trait to both sexesfrom affected male or female parents. Thissuggests that the expression of polydactyly isindependent of sex. Temtamy6 also reportedequal expression of this trait in the two sexes.

The University Grants Commission, Govern-ment of India, New Delhi is gratefully ack-nowledged for providing financial supportunder the DSA programme. Thanks are due toDr B K Patel, Government Veterinary Officerin the area, for help in collecting the necessaryinformation.

1 Castilla E, Paz J, Mutchinick 0, Munoz E, Giargivtti E,Gelman Z. Polydactyly: a genetic study in South America.Am J Hum Genet 1973;25:405-12.

2 Woolf CM, Woolf RM. A genetic study of polydactyly inUtah. Am J7 Hum Genet 1970;22:75-8.

3 Ohkura K. Clinical genetics of polydactylism. Jpn J HumGenet 1956;1:1 1-23.

4 Neel JV. A study of major congenital defects in Japaneseinfants. Am J Hum Genet 1958;10:398-445.

5 Shiota K, Matsunaga E. A genetic and epidemiologic studyof polydactyly in human embryos in Japan. Jpn J HumGenet 1978;23: 173-92.

6 Temtamy SA. Polydactyly. In: Bergsma D, ed. Birth defectscompendium. 2nd ed. New York, MacMillan, 1979:814.

7 Graham JM, Brown FE, Hall BD. Thumb polydactyly as apart of the range of genetic expression for thenar hypo-plasia. Clin Pediatr 1987;26:142-8.

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