Fibrous dysplasia is a genetic skeletal disorder in which normal bone is replaced by fibrous bone tissue. The affected bone weakens and breaks or deforms more easily. The condition usually causes no signs, but some patients quickly experience bone pain, bone deformities and bone fractures. Occasionally, rare symptoms such as hormonal problems and hearing and vision problems also occur. The disease cannot be cured, but the doctor treats the symptoms supportively with medication, orthopedic aids and surgery. Fibrous dysplasia was first described in the medical literature in 1938 by Dr. Lichtenstein.

• Synonyms of fibrous dysplasia
• Epidemiology: Mainly in children and young adults
• Causes: Replacement of normal bone by fibrous bone tissue
• Risk factors of genetic disorder
• Symptoms: Bone pain, bone abnormalities and fractures

• Locations
• Common signs
• Rare symptoms

• Diagnosis and examinations
• Therapy
• Prognosis
• Complications of bone disease

Synonyms of fibrous dysplasia

Synonyms of fibrous dysplasia (FD) include:

• Jaffe-Lichtenstein disease
• fibrous dysplasia of the bone

Epidemiology: Mainly in children and young adults

Fibrous dysplasia mainly occurs in children and young adults. In three out of four patients, symptoms manifest before the age of thirty. The highest incidence is between three and fifteen years. Patients with more than one bone affected usually develop symptoms before the age of ten. Both men and women are affected; the disease is equally common in both sexes.

Causes: Replacement of normal bone by fibrous bone tissue

A gene mutation (genetic change) is the basis of fibrous dysplasia. This genetic change occurs already after fertilization in the early stages of fetal development. The gene that is changed is responsible for the cells that produce bone. Patients with fibrous dysplasia carry this mutation in some, but not all, cells of their body. It is not clear why this mutation occurs in October 2020. The condition cannot be passed on to children and the disease is not inherited from a parent.

Risk factors of genetic disorder

Fibrous dysplasia appears in isolation, but sometimes the disease is also part of a genetic condition, such as McCune-Albright syndrome (disorder with bone, hormone and skin symptoms) and Mazabraud syndrome.

Symptoms: Bone pain, bone abnormalities and fractures

Locations

One bone (monostotic) (most common) or multiple bones (polyostotic) have been replaced by fibrous bone. Fibrous dysplasia potentially affects every bone in the body. The most common places are the bones in:

• the ribs
• the skull
• the pelvis
• the femur
• the face
• the humerus
• the Shin

 Headaches occur occasionally / Source: Concord90, Pixabay

Common signs

Most patients have no complaints due to the disease. Symptomatic patients have mild, moderate to severe symptoms. Bone pain, bone abnormalities or an increased risk of fractures (broken bones, especially in the arms and legs) and unexplained swelling are characteristic. Furthermore, the symptoms depend on the type of bone that is affected. For example, when the bones of the legs have different lengths, weakness occurs and a patient will walk lame. When bones of the sinuses are affected, a chronic nasal congestion or headache occurs.

Rare symptoms

In rare cases, fibrous dysplasia is associated with abnormalities in the hormone-producing glands of the endocrine system. This leads to premature puberty, hyperthyroidism (overproduction of thyroid hormone), an excessive amount of growth hormone in the body (gigantism or acromegaly) and/or excessive cortisol production (Cushing’s syndrome). Furthermore, hyperpigmentation on the skin (light brown spots on the skin) sometimes occurs. If the facial or skull bones are affected, bone expansion occurs, resulting in pressure or displacement of the adjacent structures. This is especially true for fibrous dysplasia that affects the skull and facial bones. This sometimes causes loss of vision or hearing.

Diagnosis and examinations

Diagnostic examination To detect the damage caused by the condition, the doctor uses several diagnostic examinations:

• a biopsy of the affected bone
• a bone scan
• a CT scan
• an MRI scan
• an x-ray

Differential diagnosis Due to the variability of the appearance of fibrous dysplasia, many conditions have a similar clinical picture.

• an adamantinoma
• a giant cell tumor
• a non-ossifying fibroma (skin growth on the stalk)
• simple bone cyst
• enchondromatosis
• neurofibromatous type I (skin and eye abnormalities)
• osteofibrous dysplasia
• Paget’s disease (chronic inflammation of the bone)

Therapy

There is no cure for fibrous dysplasia as of October 2020, but any symptoms that may be present can be treated supportively. The doctor uses bisphosphonates. These medications reduce bone pain. A fracture requires a plaster cast or splint. Deformities or severe fractures require surgery to treat the fractures or correct deformed bones. Surgical intervention is also useful for relieving the pain. Furthermore, the patient must exercise enough and also consume sufficient calcium, phosphorus and vitamin D. Radiation therapy is not recommended for patients with fibrous dysplasia because it is associated with an increased risk of cancer. Finally, the patient receives long-term follow-up to detect complications in time.Symptoms may recur during pregnancy / Source: PublicDomainPictures, Pixabay

Prognosis

The abnormal bone growth usually stops sometime during puberty. But the symptoms may return during pregnancy due to hormonal changes.

Complications of bone disease

The bone affected by fibrous dysplasia is weaker than normal and therefore more prone to fractures. Furthermore, the patient (who has often already had radiotherapy) is more likely to develop cancer:

• a chondrosarcoma (bone cancer that arises in cartilage tissue, rarely)
• a fibrosarcoma (cancer in fibrous tissue with pain and swelling)
• a malignant fibrous histiocytoma
• an osteosarcoma (bone cancer, most common)

The nerve in the eyes and ears are sometimes surrounded by affected bone. Severe deformities of facial bones lead to the loss of vision and hearing. However, this complication is rare. Finally, when leg and pelvic bones are deformed, arthritis (joint inflammation) develops in the joints of these bones.

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