Congenital pseudarthrosis of the tibia: analysis of the histology and the NF1 gene.
BACKGROUND
Congenital pseudarthrosis of the tibia (CPT) is frequently, but not always, associated with neurofibromatosis type 1 (NF1). Double inactivation of the NF1 gene has been reported to be the pathogenesis of CPT in NF1 cases.


METHODS
We analyzed the loss of heterozygosity (LOH) of the NF1 gene in cases of CPT with NF1 to examine whether double inactivation was seen in the case. In addition to morphological analysis, immunoexpression of differentiation markers was examined.


CONCLUSIONS
The tibia tapered with the zone phenomenon from mature to immature bone with osteoblastic rimming, resembling osteofibrous dysplasia. Osteosclerotic bowed bone with a small number of osteoclasts suggested dysfunction of bone remodeling. Fibrous tissue at the site of pseudarthrosis was associated with the periosteum and demonstrated myofibroblastic differentiation accompanied by massive cartilage formation, suggesting some misdirection during the differentiation of periosteum to myofibroblasts or chondrocytes. LOH of the NF1 gene locus was not seen in fibrous tissue. This result suggests that CPT is not accompanied by double inactivation in every NF1 case.
Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Fukuoka, Japan.
Akio
A
Sakamoto
Tatsuya
T
Yoshida
Hidetaka
H
Yamamoto
Yoshinao
Y
Oda
Masazumi
M
Tsuneyoshi
Yukihide
Y
Iwamoto
D002675:Child, Preschool; D016514:Genes, Neurofibromatosis 1; D006579:Heterozygote; D006801:Humans; D019656:Loss of Heterozygosity / Q000235:genetics; D008297:Male; D010010:Osteoclasts / Q000473:pathology; D011542:Pseudarthrosis / Q000151:congenital / Q000235:genetics / Q000473:pathology; D013977:Tibia / Q000473:pathology*