COMMENTARY

Is Perthes Disease Genetic? A Twin Study Has Answers

William T. Basco, Jr., MD, MS

Disclosures

June 15, 2016

A Twin Study of Perthes Disease

Metcalfe D, Van Dijck S, Parsons N, Christensen K, Perry DC
Pediatrics. 2016;137:1-5

Legg-Calvé-Perthes Disease

Avascular necrosis of the femoral head, Legg-Calvé-Perthes (LCP) disease, is estimated to have a prevalence of 6 per 100,000. While many small case series have postulated different factors to be associated with the development of LCP, it has been very difficult to know whether there is a familial or genetic component.

This study used data from the Danish Twin Registry to assess the frequency of LCP in monozygotic twins compared with dizygotic (nonidentical) twins. The hypothesis was that if the incidence is higher in monozygotic twins, then LCP would be expected to have a genetic component. Data from the Twin Registry from 1968 through 2014 were included in the study. The data from the registry were linked to national patient data to determine episodes of diagnosis of LCP. The analyses included 8120 pairs, only 10 of which were monozygotic twins. No monozygotic twins were concordant for LCP, meaning that no monozygotic twin pairs had both infants or children affected with LCP. There were two pairs of concordant twins among the dizygotic pairs and two concordant twins among the pairs with unknown zygosity. There was no difference in the average birthweight for the affected and unaffected twins. The authors concluded that they did not find evidence of a strong genetic component to LCP, but the findings of concordance in some dizygotic twin pairs suggests some familial clustering. They suggested that the familial clustering might be influenced more by environment than by genetics.

Viewpoint

Recent evidence has indicated a decline in the incidence of LCP. Nonetheless, I'm sure that concerns about familial clustering or a genetic component would be prevalent in the minds of parents when their child is diagnosed with LCP. However, the take-home message is still not totally clear. Siblings may be at risk, but this may be more due to issues in the family environment than actual genetic predisposition. That may be a difficult conversation to have with parents, especially given that this study does not specifically postulate what those familial environmental factors might be. Other studies have suggested pregnancy risk factors, nutritional risk factors during childhood, and other risk factors that may or may not be modifiable. In the end, the decision of whether to evaluate a nonaffected twin empirically remains part of the "art of medicine" and should be a decision made between the provider and parents.

Abstract

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