Fibrous dysplasia (FD) is a rare skeletal disorder where normal bone tissue is replaced by abnormal, fibrous, and immature bone, leading to structural weakness. This condition is caused by a somatic mutation in the GNAS gene, which is not inherited and affects Gs-alpha protein production, leading to dysregulated cell activity within the bone. The clinical presentation of FD varies greatly, ranging from an isolated, asymptomatic bone lesion to severe, widespread disease affecting the entire skeleton. Therefore, classification as a disability depends entirely on the condition’s severity and the documented functional impact it has on an individual’s ability to live and work.
Understanding Fibrous Dysplasia
The condition is broadly categorized based on the number of bones affected. Monostotic FD is the most common form, involving a single bone, and is often discovered incidentally because it typically remains asymptomatic or causes only mild symptoms. Polyostotic FD affects multiple bones and tends to be more aggressive, leading to a greater likelihood of pain, deformity, and fractures.
The polyostotic form may also be associated with two rare syndromes that involve extra-skeletal manifestations. McCune-Albright syndrome (MAS) combines polyostotic FD with hyperpigmented skin patches, often described as “café-au-lait” spots, and various hyperfunctioning endocrine problems, such as precocious puberty. Mazabraud syndrome is a much rarer variant that links polyostotic FD with the presence of multiple intramuscular myxomas, which are benign soft-tissue tumors.
Functional Limitations and Severity
The replacement of strong, mature bone with soft, fibrous tissue compromises skeletal integrity, which directly causes functional limitations. One of the most common and debilitating consequences is chronic pain, particularly when weight-bearing bones like the femur or tibia are involved. This pain can significantly limit mobility and the ability to stand or walk for extended periods.
The weakened bones are highly susceptible to pathological fractures, meaning they break under stresses normal bone would easily withstand. Repeated fractures, especially in the long bones of the legs, often lead to progressive skeletal deformities, such as the classic “shepherd’s crook” bowing of the upper femur. These bowing deformities can cause leg-length discrepancies and gait disturbances, further impacting a person’s ability to ambulate and perform daily tasks.
Fibrous dysplasia in the craniofacial region can cause significant asymmetry and facial deformity. More concerning is the potential for expanding lesions to compress nearby cranial nerves, leading to functional deficits. This compression can result in progressive vision or hearing loss, profound limitations that severely affect daily functioning and communication. The cumulative effect of pain, limited range of motion, and physical deformity often results in a reduced quality of life and may lead to the loss of independent mobility.
Criteria for Disability Recognition
In the context of US Social Security Disability Insurance (SSDI) or Supplemental Security Income (SSI), the diagnosis of Fibrous Dysplasia alone does not automatically qualify a person for benefits. Because it is a rare disorder, FD does not have its own dedicated listing in the Social Security Administration’s (SSA) Blue Book. Eligibility is instead determined by proving that the resulting functional limitations meet or equal the criteria of another listed impairment.
Applicants with FD typically attempt to meet the criteria under the Musculoskeletal System listings, such as those related to major joint dysfunction or spinal disorders. For example, a person may qualify if the disease has caused a gross anatomical deformity of a major joint that severely limits their ability to move or bear weight. If the craniofacial involvement has led to vision or hearing loss, the application may be evaluated under the listings for special senses.
If the specific medical evidence does not meet the exact requirements of a Blue Book listing, the SSA proceeds to an assessment of Residual Functional Capacity (RFC). The RFC is an evaluation of the maximum work-related activities a person can still perform despite their physical and mental limitations. This assessment considers limitations in lifting, standing, walking, sitting, and other exertional and non-exertional tasks.
Comprehensive medical documentation is paramount for a successful claim, whether attempting to meet a listing or relying on the RFC. The application must include objective evidence that clearly describes the extent of the lesions and how they restrict a person’s ability to work, including:
- X-rays
- Biopsy reports
- Treatment records
- Detailed statements from physicians
The SSA will consider the claimant’s age, education, and prior work history alongside the RFC to determine if there is any type of work they can realistically perform.