A comparative study of fibrous dysplasia and osteofibrous dysplasia with regard to Gsalpha mutation at the Arg201 codon: polymerase chain reaction-restriction fragment length polymorphism analysis of paraffin-embedded tissues

Abstract

Fibrous dysplasia and osteofibrous dysplasia are both benign fibro-osseous lesions of the bone and are generally seen during childhood or adolescence. Histologically, the features of these bone lesions sometimes look quite similar, but their precise nature remains controversial. Mutation of the alpha subunit of signal-transducing G proteins (Gsalpha), with an increase in cyclic adenosine monophosphate (cAMP) formation, has been implicated in the development of multiple endocrinopathies of the Albright-McCune syndrome and in the development of fibrous dysplasia. We studied Gsalpha mutation at the Arg201. codon in seven cases of fibrous dysplasia (six monostotic lesions and one polyostotic lesion) and seven cases of osteofibrous dysplasia using formalin-fixed, paraffin-embedded tissue, by means of polymerase chain reaction-restriction fragment length polymorphism and direct sequencing analysis. All of the seven cases of fibrous dysplasia showed missense point mutations in Gsalpha at the Arg201 codon that resulted in Arg-to-His substitution in three cases and Arg-to-Cys substitution in four cases. On the other hand, the seven cases of osteofibrous dysplasia and the normal bone used as a control showed no such mutation. These data suggest that fibrous dysplasia and osteofibrous dysplasia have different pathogeneses and that the detection of Gsalpha mutation at the Arg201 codon is quite useful for distinguishing between these lesions.

Figure 1.

Analysis of G_Sα mutations at the Arg²⁰¹ codon using RFLP. EagI digested the amplified DNA fragments (102 bp) including codon 201 of the G_Sα gene into 79-bp and 23-bp fragments in normal bones (lanes 1 and 2) and osteofibrous dysplasia (lanes 11–17). The 23-bp band was not visible in this gel, whereas mutant cases of fibrous dysplasia remained undigested (lanes 3–9). The p53 gene exon 8 segments were amplified in each case. The 134-bp segments are shown for each case. PCR using only primers was used as a negative control (lane 10). The 100-bp ladder was used as a size marker.

Figure 2.

Direct sequencing by the antisense primer P4 was performed on the fibrous dysplasia sample in lane 5 (Case FD99; 65-year-old female, ilium). The figure shows the G_Sα gene antisense sequence and indicates that the second position of codon 201 of the antisense strand was mutated from C to T, this change being the code for histidine instead of arginine (right). In normal bone, sequence analysis was performed after reamplified PCR without subsequent endonuclease digestion. The result was that arginine was encoded, and no mutation was seen (left).

Figure 3.

Fibrous dysplasia (12-year-old female, radius). Anteroposterior radiograph reveals a well-circumscribed intramedullary lesion within the proximal radius with a so-called “ground glass” appearance (white arrows).

Figure 4.

Osteofibrous dysplasia (14-year-old female, tibia). Lateral radiograph reveals an osteolytic intracortical lesion in the tibial shaft with marginal sclerosis (white arrows). In this case, an intramedullary lesion that appears to be a bone infarct can be also observed.

Figure 5.

Fibrous dysplasia (15-year-old male, femur). Slender curved trabeculae of bone and cellular proliferation of fibroblast-like cells can be observed (A). Note the bone trabeculae have no osteoblastic rimming (B). H&E; original magnifications, ×100 (A) and ×140 (B).

Figure 6.

Osteofibrous dysplasia (13-year-old female, tibia). Microscopic features are characterized by woven bone trabeculae with rimming of osteoblasts and a cellular proliferation of fibroblast-like cells. H&E; original magnification, ×140.