Clin Genet 1999: 56: 462–463Printed in Ireland. All rights reser6ed

Letter to the Editor

Postaxial polydactyly and Dandy–Walkermalformation. Further nosological comments

To the Editor:The association of postaxial polydactyly andDandy–Walker malformation or related brainanomalies can be seen in chromosomal (trisomy 13,trisomy 8), autosomal recessive (hydrolethalus,Meckel, pseudotrisomy 13), and autosomal domi-nant (Pallister Hall, Greig) syndromes. In 1996,Morava et al. (1) reported on a patient withDandy–Walker anomaly and postaxial poly-dactyly, suggesting that this combination of defectscould represent an oligosymptomatic case of hy-drolethalus syndrome. Buttiens et al. (2) and Frynsand Van den Berghe (3) described two unrelatedfamilies whose members presented with an occipitalbone defect and postaxial polydactyly as the mainfeatures, but with a wide variability of expression.With regard to these cases, and commenting on thereport of Morava et al. (1), Fryns (4) suggested thatnot only autosomal recessive, but also the men-tioned autosomal dominant syndrome should beconsidered among the differential diagnoses incases with Dandy–Walker malformation andpostaxial polydactyly.

The presence of only two malformations in aninfant, without other, perhaps minor, anomalies,which could favor the diagnosis of a specific syn-drome, frequently raises doubts as to whether weare dealing with a syndrome or an unspecific asso-ciation.

In order to evaluate the diagnostic value of theassociation postaxial polydactyly – Dandy–Walker malformation or related brain anomalies,we determined in 16 201 multiply malformed in-fants ascertained by the ECLAMC (5): 1) the fre-quency of the association between postaxialpolydactyly and unspecific hydrocephalus; and 2)the frequency of the association between postaxialpolydactyly and Dandy–Walker malformation orrelated anomalies. Finally we analyzed each of theobserved cases individually. These data partiallyoverlap with those reported by Castilla et al. (6).

As the expression of Dandy–Walker malforma-tion is variable, including hydrocephalus, anoma-lies of the posterior fossa, cerebellum, and corpus

callosum, we established the frequency of associa-tion between postaxial polydactyly and any of thefollowing anomalies: Dandy–Walker malforma-tion, anomalies of the cerebellum, corpus callosumor septum pellucidum, with or without hydro-cephalus.

Postaxial polydactyly and unspecific hydro-cephalus are frequent among multiply malformedinfants (52/1000 and 62/1000, respectively;ECLAMC data). However, they do not seem toassociate preferentially with each other. Althoughwithout statistical significance, postaxial poly-dactyly and unspecific hydrocephalus were nega-tively associated (39 observed cases, expected 52;exact probability by Poisson p=0.067).

Conversely, there was a positive association be-tween postaxial polydactyly and specific brainanomalies (Dandy–Walker and related malforma-tions) (ten observed cases, five expected; exactprobability by Poisson p=0.032).

When analyzing the records of the ten observedcases, in nine of them the pediatrician in charge ofthe malformed child had defined or suspected asyndrome, by clinical features, positive family his-tory, or parental consanguinity (trisomy 13 syn-drome 3, hydrolethalus syndrome 2, acrocallosalsyndrome 1, pseudotrisomy 13 syndrome 1, Meckelsyndrome 1, and acromelic frontonasal ‘dysplasia’1). One case with postaxial polydactyly and dysge-nesis of the corpus callosum had a positive familyhistory for polydactyly, so a random co-existenceof two independent traits seemed likely (Table 1).

In conclusion, postaxial polydactyly does associ-ate preferentially with certain specific brain anoma-lies. This fact, plus the analysis of the individualcases and the negative association with unspecifichydrocephalus, suggests that in the presence of anyassociation between postaxial polydactyly andDandy–Walker malformation or related brainanomalies, a syndrome should be suspected.

M RittlerEE Castilla

462

Letter to the Editor

References

1. Morava E, Adamovich D, Czeizel AE. Dandy-Walker mal-formation and polydactyly: a possible expression of hydro-lethalus syndrome. Clin Genet 1996: 49: 211–215.

2. Buttiens M, Fryns JP, Jonckheere P, Brouckmans-ButtiensK, Van den Berghe H. Scalp defect associated with postax-ial polydactyly: confirmation of a distinct entity with auto-somal dominant inheritance. Hum Genet 1985: 71: 86–88.

3. Fryns JP, Van den Berghe H. Congenital scalp defectsassociated with postaxial polydactyly. Hum Genet 1979: 49:217–219.

4. Fryns JP. Dandy-Walker malformation and postaxial poly-dactyly: nosological comments. Clin Genet 1997: 51: 139.

5. Castilla EE, Lopez-Camelo JS. The surveillance of birthdefects in South-America: I. The search for time clusters:epidemics. Adv Mutagen Res 1990: 2: 191–210.

6. Castilla EE, Lugarinho R, Dutra MG, Salgado LJ. Congen-ital anomalies associated to polydactyly. Am J Med Genet1998: 80: 459–465.

Correspondence:Monica Rittler, MD, PhDTucuman 3130, Olivos(1636) Buenos AiresArgentinaTel.: +54-114-799-7570Fax: +54-114-794-1630E-mail: mrittler@ciudad.com.ar

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