Fibrous Dysplasia Meets Intramuscular Myxoma: Mazabraud Syndrome—First Documented Case in Pakistan

Background: Mazabraud syndrome (MS) is a rare benign genetic disorder characterized by the coexistence of fibrous dysplasia (FD) and intramuscular myxoma (IM), with a very limited number of cases reported worldwide, and none has been documented in Pakistan until now. It typically presents in middle-aged females and affects the lower limbs. Its pathogenesis is associated with activating mutations in the GNAS gene. This disease is often under-recognized in low-income countries. It can rapidly progress to bone deformities, fractures, and unnecessary aggressive treatments if not promptly recognized. Case Presentation: A 64-year-old male presented with progressive fatigue and pallor for three months, alongside a lifelong history of multiple bone deformities and painless soft tissue swellings. He had recurrent fractures since childhood, leading to severe limb deformities and dependence on crutches. Physical exam revealed bosselated swellings over the axilla, thigh, and groin, with significant limb shortening. Imaging showed widespread lytic lesions and necrotic soft tissue masses. Blood work revealed hypochromic microcytic anemia with rouleaux formation; white cell and platelet counts were normal. Bone marrow biopsy demonstrated Grade III myelofibrosis with characteristic "Chinese letter" trabeculae, confirming FD. Biopsy of soft tissue masses showed benign IMs. A diagnosis of MS was made based on the coexistence of polyostotic FD and multiple myxomas. Conclusion: MS is a rare and benign genetic disorder that requires a high index of suspicion for timely diagnosis. This unique case underscores the need for increased clinical awareness of MS in resource-limited settings where genetic testing is not common and the importance of multidisciplinary evaluation for accurate diagnosis and management. Timely diagnosis and treatment can prevent bone deformities, fractures, and disabilities and improve patient outcomes for this uncommon syndrome.