Short, practical answers to the questions families most often raise after a fresh diagnosis. Fuller treatment of each topic is on the other subpages.
Not in most cases. The GNAS gene mutation is somatic - it arises spontaneously during early embryonic development. This means it is not passed down from parents and usually does not recur in siblings.
Not necessarily. Leading global centers (Leiden UMC, Sapienza, UCSF) and the FD/MAS Consortium 2019 guidelines recommend observation until skeletal maturity in the absence of pain or functional impairment. Any surgical decision should be made jointly with a clinician experienced in FD.
There is no single center specializing in FD. It is a rare disease and most clinicians encounter it at most a few times in their career. We are building a database of clinicians in Poland and Europe who have treated FD/MAS patients - with their current affiliation and specialty.
Not always - and two things matter here at once. First: in typical cases, FD/MAS is diagnosed from the clinical and radiological picture, without a biopsy (in line with the FD/MAS International Consortium guidelines). In the craniofacial form, an experienced maxillofacial surgeon may recommend observation rather than surgery on that basis. Second: if a biopsy has already been done, histopathology alone is often not enough - especially when the result points to a different lesion, e.g. juvenile trabecular ossifying fibroma (JTOF), which is treated surgically. The microscopic picture of FD and JTOF can be strikingly similar, so a GNAS mutation test on the biopsy material (a marker specific to FD) is what settles it. The material of choice is a paraffin block from the lesion (about 80% detection). The mutation is detected from blood far less often, because it is present in only some cells (mosaicism), and when the lesion is single and in one bone it is usually absent from blood altogether. So a negative blood result excludes nothing, while a positive one confirms the disease.
Fibrous dysplasia is a benign, non-cancerous lesion. But the histological picture can resemble other bone lesions - such as Juvenile Ossifying Fibroma - which is why the GNAS genetic test matters for a correct diagnosis. FD does not metastasize and is not life-threatening in the way cancers typically are.
Yes - this is the polyostotic form. It can affect many bones at once and co-occur with hormonal disorders. This form is part of a broader spectrum known as McCune-Albright syndrome (MAS).
McCune-Albright Syndrome (MAS) is a form of fibrous dysplasia combined with endocrine disorders - e.g. precocious puberty, thyroid problems, hyperparathyroidism, café-au-lait skin patches. MAS patients need endocrinologist care in addition to an orthopedist or maxillofacial surgeon.
Yes. The FD/MAS Consortium 2019 published a consensus in Orphanet Journal of Rare Diseases, which is open-access - you can download it and bring it to a consultation. The FD/MAS Alliance website also publishes diagnostic flowcharts (skeletal evaluation, bone pain management, MAS endocrine care, craniofacial FD management).
Yes. Denosumab (anti-RANKL) is used for rapidly growing lesions. Burosumab (Crysvita), registered in the USA and Europe for X-linked hypophosphatemia, is administered off-label in some centers for FD patients with hypophosphatemia. Research is also ongoing on therapies targeting overactive cAMP/Gs-alpha signaling.
You can help in several ways: a financial donation (transfer, 1.5% CIT, planned campaigns), submitting an experienced clinician to the database, sharing the website with other families or clinicians, or volunteering (medical, legal, technical).