Terminal phalangeal accessory ossification center of the thumb: an additional radiographic finding in Larsen syndrome
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Larsen syndrome is an autosomal-dominant disorder characterized by multiple joint dislocations, vertebral anomalies and dysmorphic facies. Both autosomal-dominant and autosomal-recessive forms of the disorder have been proposed. Individuals with autosomal-dominant Larsen syndrome have characteristic “cylindrical-shape” thumbs caused by broad, shortened phalanges. Autosomal-dominant Larsen syndrome results from heterozygosity for mutations in filamin B, a cytoskeletal protein involved in multicellular processes. We report here a patient with a duplicated or accessory distal thumb phalanx and multiple large joint dislocations who was shown to be heterozygous for a filamin B mutation predicting the amino acid substitution G1691S. This adds a new radiographic finding, duplicated or accessory distal phalanx, to the radiographic abnormalities seen in this rare dominant disorder.
KeywordsBifid thumb Accessory thumb ossification Larsen syndrome Filamin B
The authors wish to thank the patient, the family and the family’s physicians for participating in the study described here. The work was supported in part by grants from the NIH (HD22657) and the Joseph Drown Foundation to D.K. and by the NIH-sponsored General Clinical Research Center Grant M01-RR00425 to Cedars-Sinai Medical Center. Y.A. was supported by a grant from the Scientific and Technological Research Council of Turkey (TUBITAK).
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