Introduction
Hereditary multiple exostosis is a rare genetic disorder that mainly affects males. Hereditary multiple exostoses is a genetic disease characterized by multiple osteochondromas (non-cancerous bone tumors). It grows near the growth plates of bones. The affected sites are the pelvis, ribs, vertebrae, and long bones. It is also called hereditary multiple osteochondromas. Hereditary multiple exostoses mainly occur due to gene mutation (harmful changes) or the function of genes, such as EXT1 and EXT2 genes. The genes EXT1 and EXT2 encode the glycosyltransferase, which is used to synthesize heparan sulfate. Hereditary multiple exostoses involve the symptoms such as chronic pain (pain which stays longer than three months), limb deformity, restriction in motion, short stature (short in length), scoliosis (backbone with sideways curvature, and alteration in the neurovascular system. Sometimes malignant transformation can be seen. Managing hereditary multiple exostosis surgery is the only treatment choice because no medical treatment is available. This article explains hereditary multiple exostosis's causes, symptoms, diagnosis, and treatment.
What are Hereditary Multiple exostoses?
Hereditary multiple exostoses (HME) are also called familial osteochondromatosis or diaphyseal aclasis. It is an inherited rare genetic disorder. HME is relatively rare as its prevalence is 1 per 50,000 individuals. This disease depends mainly on the number and shape of the growth of tumors. The condition is asymptomatic, which results in remaining undiagnosed.
Hereditary multiple exostoses is a condition in which the development of multiple benign bone tumors (non-cancerous) and are also called osteochondromas. This disease can involve any site of bone, especially at the end of long and flat bones. This disease involves facial bone, or any bone originating from endochondral ossification (inner layer of the bone).
It starts mainly from the scapulae, ribs, and pelvis. According to the studies, there is no involvement of the skull, bones of hands, and feet. It mainly occurs in males, as 50 % of the patients inherit this disease from their fathers. Hereditary multiple exostoses are not present from birth but occur mostly at twelve. This disease gets diagnosed at an early age (before 10 years). HME affects the quality of life and can cause severe symptoms based on the location of tumors. It affects mental health and childhood. Patients with HMEs live compromised life after surgery on the limbs. The surgery of the limbs or affected face can cause severe deformity.
What Are the Causes Of Hereditary Multiple Exostoses?
Hereditary multiple exostosis is a rare genetic disorder with the formation of multiple noncancerous tumors on the bone. The root causes of hereditary multiple exostosis are not known. According to the studies, HME results from harmful gene changes such as EXT1, EXT2, and EXT3. These genes are important in synthesizing heparan sulfate necessary for various biological activities. According to researchers, 5 to 34 percent of patients are undetected, affected by HME mutation in the EXT1 and EXT2 genes.
What Are the Symptoms Of Hereditary Multiple Exostosis?
The specific symptom of multiple hereditary exostoses is the formation of exostosis (benign growth of cartilaginous tissue on a bone). Patients affected with HME seem to have palpable masses at the joints. The most affected joints are the knees, shoulders, ankles, and wrists. The deformation is characterized by affecting the distal femur, radius, ankle, and ulna. It creates aesthetic issues also when the tumors develop on the ribs and proximal tibia. Sometimes the acetabulum tumors convert into acetabular dysplasia, then femoroacetabular impingement, and at last, it leads to juvenile arthritis. In this situation, arthroplasty is done to manage the disorder. In one-third of the patients affected with HME, the most frequently seen condition is genu-valgum (when knees angle touch each other) at the lateral surface of the tibia. Up to 60 percent of the patients affected with HME have spinal exostoses or spinal osteochondromas, which causes sudden or severe neurological syndromes. Some of the patients develop chronic inflammation syndromes with restricted motion or paresthesia (damaged nerves with tingling and pricking sensation). Patients also suffer from chronic pain syndromes and have poor quality of life.
How Can Hereditary Multiple Exostoses Be Diagnosed?
Hereditary multiple exostoses mainly occur at the site of a bone, so it is mainly present with no symptoms at the initial stage. At three years of age, it can be diagnosed. At the age of five years, the tumors are visible in fifty percent of cases. For the detection and study of hereditary multiple exostosis, X-rays are useful. It is also diagnosed with ulnar shortening and deformity focusing on the bayonet hand (wrist deformity) and distal femur deformity. Recently osteochondromas have been detected on the perichondrium layer. Investigation such as genetic, molecular, biological, and clinical investigation are important for the diagnosis of hereditary multiple exostosis. There is a palpable mass near the joints of the knees, shoulders, ankle, and wrist.
What Are The Treatments For Hereditary Multiple Exostoses?
According to studies and research, no medical treatment is available for multiple hereditary exostoses. Still, the researchers suggest that therapeutic options will be present in the future for managing this disease. A higher level of heparanase inhibitor (SST0001) is used to inhibit irregular chondrogenesis because it interferes with HS, BMPs, and chondrogenesis. Palvarotene can treat the fibrodysplasia ossificans progressiva (FOP). The treatment for HME patients is symptomatic and surgical. The surgical removal of osteochondromas is an easy process, but it becomes difficult to operate in some sites, such as the lateral surface of the femur. The surgical excision involved the removal of the base of the bone following the removal of the cartilage cap. Suppose the cartilaginous cap is removed once there is less chance to re-occurrence of this tumor again. The most common complications after the surgical excision of osteochondromas are neurapraxia, so aggressive surgical removal is not suggested.
Conclusion
Hereditary multiple exostoses are a rare genetic disorder. For prevention and initial correction of deformities of bone affected by multiple hereditary exostoses, lengthening of the affected sites is recommended. In recent studies, many techniques have been applied in the field of pediatrics and orthopedics so that the affected child gets therapy in their initial phase. It will improve the quality of life as well as their functional activities.
