Ollier disease is a rare genetic disorder leading to benign skeletal tumors or enchondromas that usually develop in the cartilage at the end of growing bones. Most people with the disease begin developing these tumors in early childhood, and the growth ends when the bones finish growing in early adulthood. The result of these enchondromas is bone deformities that can affect physical ability.
The Role of Cartilage in the Body
Cartilage is composed of connective tissue and, in embryos and children, provides a model for future bone growth. Through adolescence, thin plates of cartilage remain at the ends of growing bones until early adulthood, when the plates ossify, turning to bone.
What Are Enchondromas?
Enchondromas are typically benign. The tumors develop within the cartilage of growing bones, most commonly the hands and feet, when there is an overgrowth of bone cartilage or abnormal, continued growth of embryonic cartilage. Some may become cancerous through a process called malignant transformation.
What Causes Ollier Disease?
Ollier disease is most often caused by a mutation in the IDH1 or IDH2 genes that provide instructions for enzyme function in specific cellular processes. The mutation results in abnormal enzyme activity, which, in turn, prompts the excessive bone growth that leads to enchondromas. Researchers have also discovered that the mutation of other genes can cause Ollier disease.
Somatic Mutation in Ollier Disease
Most cases of Ollier disease are not genetically inherited. The mutation responsible for the development of the disease is somatic, meaning it occurs in fetus development. In inherited genetic disorders, the genetic mutation exists in every cell in a person’s body. In Ollier disease, however, the mutation randomly develops in just one cell. Every cell that originates from this cell carries the mutation.
Signs and Symptoms
Enchondromas are the telltale markers of Ollier disease. They develop primarily on the hands and feet and occasionally the skull, ribs, pelvis, and arm and leg bones. The tumors appear as masses beneath the skin and may be painful. Other signs include skeletal deformities, shortening of the limbs, and short stature. These signs are usually unilateral, which means they occur on only one side of the body.
Complications of Ollier Disease
Multiple enchondromas can cause fractures, underdeveloped muscles, and curving or bending of the bones on which the growths develop. Tumors near joints may cause pain during movement and immobility. Limb asymmetry, particularly in the legs, can lead to abnormal gait and discomfort when walking.
Rarely, benign enchondromas become cancerous due to malignant transformation. The tumors most often develop into chondrosarcoma, cancer that affects the bones and surrounding soft tissue. The development of chondrosarcoma occurs in around 25% of those with Ollier disease. The condition also increases a person’s risk of developing cancer elsewhere in the body, most often the ovaries and liver.
How is Ollier Disease Diagnosed?
Ollier disease is typically diagnosed with a physical exam and symptoms. The markers are well-recognized, and a doctor may be able to make a preliminary diagnosis based on observable skeletal deformities before ordering further tests. A CT or MRI scan, x-ray, or biopsy of the enchondroma can confirm the diagnosis.
Treating Ollier Disease
The approach a doctor takes to treating Ollier disease depends on several factors, including the disease’s impact on physical ability, the amount of pain and discomfort the person experiences, and complications. Most experts do not recommend surgery because it can lead to the development of more tumors. Physical therapy is the most common course of treatment, to help individuals manage pain and adapt their movements.
The prognosis for a person diagnosed with Ollier disease depends on the density of the enchondromas, the age of onset, and the impact of the disease on physical ability and comfort. The overall outlook is, however, good, and most people with the disease live with minimal limitation.