Baastrup's Disease: a poorly recognised cause of back pain.

A 56-year-old male, with a personal history of obesity (BMI – 50Kg/m), depression, arterial hypertension, obstructive sleep apnea syndrome and gout, complained about progressive mechanical back pain for more than 10 years. The condition worsened with prolonged orthostatism and spine extension and improved in fetal position. His lumbar spine radiography (Figure 1) revealed enlargement and sclerosis of the spinous processes which was confirmed by computed tomogra phy (CT) (Figures 2 and 3), suggesting Baastrup’s disease. This condition, although previously recognized by others authors, was described in detail by Baastrup, in 1933. It is characterized by enlargement, close approximation and impingement of one spinous process on another (“kissing spines”). There are few studies on Baastrup’s disease epide miology and their results are inconsistent. A retrospe ctive study analyzed the frequency of Baastrup’s disease evidence in abdominopelvic CT scans of 1008 patients, reporting a prevalence of 41%. After the age of 80, prevalence was 81.3%. Another study determined the prevalence of interspinous bursitis in 539 symptoma tic patients who underwent magnetic resonance (MRI) and obtained a result of 8.2%. A smaller study using a diagnostic algorithm to evaluate 156 patients with recurrent back pain, found 3 cases (1.8%) in which Baastrup’s disease was responsible for the symptoms. Patients often complain of back pain, typically increased with extension and relieved by flexion. Radiographically, spinous process impingement leads to reactive sclerosis, enlargement, flattening, and remodeling of the involved vertebral spines. Physicians frequently miss it on radiographs due to lack of know ledge and overexposure of spinous processes in most X rays. This abnormal contact between adjacent spinous processes can result in neoarthrosis and formation of an adventitious bursa, which can be seen pathologically and on MRI. Differential diagnosis should be made with other causes of low back pain, more frequently lumbar internal disc disruption, facet joint pain and sacroiliac joint pain. Both conservative and surgical options are available for treatment. It may improve with localized interspinous injection of anesthetic and there are conflicting reports of improvement with partial excision of the spinous process. In conclusion, Baastrup’s disease should be conside red in differential diagnosis of back pain, although one ACTA REUMATOL PORT. 2015;40:302-303