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Mazabraud syndrome is a rare benign mesenchymal disorder characterized by the association of:

1. Polyostotic fibrous dysplasia (FD)
2. Intramuscular myxomas </aside>

It is considered part of the spectrum of post-zygotic activating mutations involving the GNAS gene.

Epidemiology

• Rare
• More common in middle-aged women
• Intramuscular myxomas usually appear years after diagnosis of fibrous dysplasia

Pathology

Fibrous dysplasia

A benign fibro-osseous lesion where normal bone is replaced by:

• immature woven bone
• fibrous stroma

Intramuscular myxoma

Benign soft tissue tumor composed of:

• hypocellular myxoid stroma
• sparse spindle cells
• abundant mucopolysaccharide matrix

Clinical Features

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Common sites: Thigh, gluteal region, upper arm

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