Is fibrous dysplasia serious?

Fibrous dysplasia is a disease caused by pathological changes in bone growth and development. Clinically, it mainly causes bone damage and is a relatively serious disease. Patients are often children who may suffer from precocious puberty if they do not pay attention to good treatment. In addition, skin pigmentation is also a relatively common hazard and can also affect the endocrine system. Let us learn more about this aspect.

Is fibrous dysplasia serious?

1. Bone damage

Bone damage is mainly focal lesions. The focal lesions consist of fibrous connective tissue with scattered immature interwoven bone fragments and nodules of cartilaginous tissue. Bone damage often manifests as expansion of the bone marrow cavity into the bone cortex, leading to thinning of the bone cortex. Some local lesions of multiple fibrous dysplasia may have liquefaction, cystic change, hemorrhage and ossification in the cartilage nodules, forming focal deformities. Involvement of the weight-bearing parts of the bones may lead to lameness or even pathological fractures.

The above lesions can affect bones throughout the body and can be divided into single-type and multiple-type according to the nature of the lesions. Single cases are most commonly found in the femur, tibia, and ribs, and are relatively uncommon in the spine and pelvis. 30% involve the craniofacial bones, but mainly the maxillary and mandibular bones and the top of the skull. Bone hyperplasia and sclerosis at the skull base often compresses cranial nerves, leading to optic nerve atrophy. Excessive growth of facial bones causes facial asymmetry and sinus obstruction. Damage to the spine, pelvis, and long bones of the limbs leads to bone deformities, pathological fractures, and bone pain. Multiple cases mainly affect both sides or one side of the body, with the lower limbs, femur, tibia and pelvis being more common. The ribs and skull are less frequently affected, and the skull base may be affected.

2. Skin pigmentation

Skin pigmentation occurs on the same side of the bone lesion, appearing as localized dark brown flat spots. Typical pigmented spots are called Cafe-au-lait spots, which are irregular in shape and often distributed in small flakes. Skin pigmentation is more common on the back, but also on the lips, neck, waist, buttocks, and thighs. Pigmentation spots may not be obvious at birth, but they become more severe and darker with age or exposure to sunlight. The appearance of the pigmentation is related to the amount of bone lesions. If the edge of the pigmentation is clear, usually only a single bone is affected; if the edge is unclear and presents a map-like shape, usually multiple bones are affected.

3. Precocious puberty

It is more common in females, and the age of precocious puberty is usually before 6 years old, with an average development age of 3 years old. There have been reports of precocious puberty occurring in the first month after birth. Menstruation is the primary symptom of precocious puberty in women, occurring before breast development. Plasma estrogen levels fluctuate between normal and significantly elevated (>900pg/ml), often in a cyclical manner. LH and FSH levels in young females are suppressed and do not respond to GnRH stimulation (except in adult patients), indicating that precocious puberty in girls is not dependent on gonadotropin. Precocious puberty in women is consistent with bone age. The long-acting GnRH analog cyproheptadine is ineffective in treating prepubertal patients. However, the aromatase inhibitor testosterone has a significant therapeutic effect on girls.