Diffuse Idiopathic Skeletal Hyperostosis

Despite the fact that many patients with DISH are asymptomatic, numerous symptoms have been reported, and they depend on the localization of skeletal changes. In the case involvement of the thoracal spine, which is the most common localization, back and neck pain, limited range of motion, stiffness, and increased frequency of spinal fractures have all been documented [10], while dysphagia is the principal symptom in cervical spine involvement. Since other parts of the skeletal system may be affected, polyarticular pain, tendinitis, and in severe cases, spinal compression and numbness in lower extremities may be observed [11]. The differential diagnosis of DISH is broad and includes numerous systemic diseases, which is why a thorough diagnostic workup is necessary to exclude other diseases, including ankylosing spondylitis, different spondyloarthropathies, and spondylosis deformans.

The diagnosis of DISH is performed according to specific diagnostic criteria supported by various imaging studies. Resnick and Niwayama proposed criteria that include the following [12]:

• Calcification and ossification of ventrolateral aspects of at least four contiguous vertebrae, with or without excrescences at the vertebral disc-body junctions.
• Preservation of disc height and integrity in areas where DISH developed, and absence of radiological findings that may indicate degenerative disease.
• The absence of apophyseal joint, bony ankylosis, and absence of erosion and sclerosis of the sacroiliac joint.

For patients to be evaluated using this criterion, imaging studies are imperative. Usually, plain radiography can show abnormal bone formation and multiple large calcifications along the vertebral column, particularly if the changes occur in the thoracal spine, and almost all patients have involvement of the thoracic vertebrae. Extraspinal calcifications may be observed in numerous joints, including the calcaneus, olecranon, metacarpal and phalangeal joints of the hand, in which capsular hyperostosis is observed in more than 10% of patients [13].

Despite the fact that plain radiography is effective in recognizing the changes in DISH, CT and MRI studies are more effective in determining the magnitude of the lesions. More importantly, they are helpful in assessing complications and associated findings, such as compression of the spinal cord, as well as tracheal and esophageal obstruction. These findings can be of great value in determining whether surgical therapy should be instated in these patients.

Treatment of DISH is targeted at alleviating symptoms that occur as a result of the disease, and treatment is often unnecessary in asymptomatic patients. Depending on which part of the skeletal system is involved and the severity of complaints, treatment involves rehabilitation, lifestyle changes, pain alleviation with non-steroidal anti-inflammatory drugs (NSAIDs), and in severe cases, surgery.

For patients with little or no complaints, pain can be managed with NSAIDs, including paracetamol and ibuprofen (unless these patients present with contraindications, such as peptic ulcer disease), while regular exercise and proper dietary habits have been established to be important in these patients.

For patients with dysphagia, and mechanical obstruction of respiratory and gastrointestinal passages, initial tracheostomy and subsequent osteophysectomy is indicated, and shows good results [14].

Because DISH uncommonly produces symptoms, the long-term prognosis is generally good. In rare cases, however, cervical spine involvement may lead to significant complications, which necessitate surgical treatment. For these reasons, a prompt workup is necessary for patients who are symptomatic, but with proper therapy, the outcomes are very good. The disease itself does not pose a significant risk to the patient and shows a slow progression. In fact, several studies established a less frequent presence of back pain and similar symptoms in patients with DISH compared to control subjects.

The cause and pathogenesis of DISH remain unknown. However, several factors, including mechanical, genetic and environmental have been determined to play a role in the etiology of this disorder [4]. Aortic pulsations and its pressure on the adjacent skeletal structures, HLA mutations, exposure to fluoride, use of isotretinoin and other derivatives of vitamin A, and degenerative changes have all been hypothesized to contribute to this disease, but no solid conclusions have been made yet. Metabolic diseases, such as diabetes mellitus and acromegaly, and other diseases in which cartilage development is impaired, have also been investigated as potential factors in the development of DISH.

Certain studies estimated that prevalence rates for DISH are approximately 19% for men and 4% for women older than 50 years, with small variations [5] [6]. Prevalence rates increase as the age increases, and certain studies have determined that DISH is present in more than 30% of males older than 65 years, and more than 50% of males older than 80 years [7]. These studies have also identified that blood pressure and increased body mass index (BMI) positively correlated with the development of this disorder. DISH very rarely occurs in adults under 40 years of age, while ethnic predilection has not been documented yet.

The hallmark of DISH is ossification of entheses - bony attachments of ligaments, tendons, and joint capsules, and development of osteophytes. As a result of these changes, numerous pathological features are observed, including focal and diffuse calcifications, periosteal bone formation on the surface of vertebral bodies, paraspinal connective tissue fibrosis, and many other [8]. When these changes occur in the cervical spine, development of large osteophytes may lead to direct compression of the esophagus, resulting in dysphagia, while tracheal displacement and airway compromise may also occur [9]. Spinal cord compression open link and increased risk of fractures are also established in these patients because of the changes that occur in patients with DISH.

It is important to distinguish DISH from other skeletal diseases of similar pathogenesis, such as ankylosing spondylitis since this disorder produces non-inflammatory changes in the skeletal system.

The means of direct prevention of DISH are currently not established. However, since this disease is associated with obesity, hypertension, and metabolic diseases such as diabetes mellitus, preventive measures may include proper dietary habits and regular physical exercise.

Diffuse idiopathic skeletal hyperostosis (DISH) is a generalized skeletal disease which is characterized by ossification of bony entheses, including tendons, ligaments, and joint capsules, with resultant development of osteophytes [1]. Since its initial description in the 1950s [2], numerous advances have been made in terms of epidemiology, diagnosis, and treatment, but the cause of DISH remains unknown. It is established that this disease is more present in men than women and that it is most commonly diagnosed in males older than 50 years. The thoracal spine and the anterior longitudinal ligament is described as the most common location of this disease. Cervical spine, the pelvis, calcaneum and ulnar olecranon are also sites where this disorder is reported [3]. Although the majority of patients are asymptomatic, patients may have significant complaints, depending on the site of ossification. Thoracal spine involvement is usually accompanied with back pain and stiffness, and if the cervical spine is affected, hyperostosis may lead to dysphagia and breathing difficulties, as a result of mechanical obstruction of the trachea and the esophagus. Other symptoms include localized pain and development of fractures. The diagnosis is made by imaging studies, which reveal large calcifications and computed tomography (CT scan) and magnetic resonance imaging (MRI) are superior to plain X-rays in diagnosing DISH and other associated findings. Diagnostic criteria include ossification of at least 4 contiguous vertebrae, preservation of the intervertebral disc space and its height, and absence of apophyseal joints, ankylosis, erosion or other sacroiliac inflammatory changes. Treatment is often delayed, as many patients do not report symptoms. Physical therapy is an important part of the long-term management of patients who report pain and reduced motion, and lifestyle, as well as dietary habit changes, are also indicated. Appropriate therapeutic and surgical procedures are necessary for patients with the compromise of the airway and the esophagus, including tracheostomy and osteophysectomy, to reestablish safe passage of air and food content.

Diffuse idiopathic skeletal hyperostosis (DISH) is a disease in which the sites where tendons and ligaments attach to the bone tend to transform into bone tissue and result in the extensive bone growth and calcifications. It is still unknown why this disease occurs, and it is thought that mechanical, genetic, and environmental factors all play a role in the pathogenesis of this disease. It is established that the risk factor for DISH is male gender and increased age, because the rates of DISH rise as the age increases, and certain studies indicate that more than 30% of males over 65 years have this disease. This disease is very rarely seen before 40 years of age. Additionally, it was established that blood pressure and obesity correlate with this disease, which provides evidence that dietary and lifestyle habits are important in preventing this disorder. DISH can occur at any site in the body. The most common location where DISH develops is the spine, but other sites are reported as well, including the hips, elbows, the patella, and the bones of the hands and feet. The majority of individuals with DISH are asymptomatic, but when symptoms are present, they include pain, back stiffness, and limited range of motion. When DISH develops in the vertebrae of the neck, direct compression of the airways and gastrointestinal tract may occur, which can lead to symptoms of painful and difficult swallowing, voice changes, and breathing difficulties. The diagnosis of DISH is made by performing a plain X-ray, which can clearly show the presence of calcifications, and virtually all patients have these calcifications in the spine. Computed tomography and magnetic resonance imaging are used in assessing potential complications, including compression of the airways, and can detect other associated findings, such as spinal cord compression, which occurs in rare cases. Treatment involves symptomatic therapy, including pain relief, rehabilitation, and if necessary, surgical treatment to correct the changes that occurred as a result of this disease. The prognosis is generally good, as the disease does not pose a threat to the patient, but in the case of the airway compromise, prompt surgical therapy is vital in preventing the occurrence of other complications. Because this disease is correlated with increased blood pressure and obesity, proper dietary habits and regular physical exercise have been implicated as measures of prevention against DISH.

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