A 38-year-old man is evaluated due to a 2-year history of gradually worsening low back pain, bilateral buttock pain, and stiffness. Symptoms are worse in the morning and relieved with stretching and hot showers. The patient also has fatigue but no fever, chills, night sweats, or weight loss. Vital signs are normal. The patient appears healthy but has a stooped walking posture. Deep palpation over the lumbar spine at the midline and both sacroiliac joints elicits tenderness. Erythrocyte sedimentation rate is 75 mm/hr. Which of the following pathologic findings is most likely causing this patient's symptoms?

Question

A 38-year-old man is evaluated due to a 2-year history of gradually worsening low back pain, bilateral buttock pain, and stiffness.  Symptoms are worse in the morning and relieved with stretching and hot showers.  The patient also has fatigue but no fever, chills, night sweats, or weight loss.  Vital signs are normal.  The patient appears healthy but has a stooped walking posture.  Deep palpation over the lumbar spine at the midline and both sacroiliac joints elicits tenderness.  Erythrocyte sedimentation rate is 75 mm/hr.  Which of the following pathologic findings is most likely causing this patient's symptoms?

Quizplus · Accepted Answer

11ec160b_3a54_0952_9249_639d589cb993_MD0001_00 This patient presenting with chronic back and buttock pain associated with stiffness has ankylosing spondylitis (AS). The symptoms are characteristically worse in the morning and improve with stretching and warm showers. AS is most common in men age <40, and inflammatory markers (eg, erythrocyte sedimentation rate [ESR]) are usually elevated. AS is characterized by simultaneous erosion of bone and new bone formation, unlike rheumatoid arthritis in which only erosions are seen. The initial pathogenesis is driven in part by inflammatory cytokines (eg, tumor necrosis factor, IL-17), which cause activation of osteoclast precursor cells and bony erosions. This occurs primarily in the vertebral bodies and results in destruction of the microarchitecture, increasing the risk for secondary osteoporosis and compression fractures. Once the inflammation subsides, the reparative process leads to excessive new bone formation (especially in areas where fat metaplasia fills previously eroded sites); in contrast to erosion, bone formation occurs primarily at the periosteum-cartilage junction and manifests as bridging syndesmophytes in the vertebral column. This leads to spinal rigidity, postural alterations, and increased risk of fracture. (Choice B) Fibrous dysplasia is a benign bone tumor characterized by focal bone dysplasia with spindle cells. It typically presents as asymptomatic lytic lesions, most commonly in the femur and tibia. Fibrous dysplasia is usually seen in children and is not an inflammatory condition (ie, normal ESR). (Choice C) Paget disease of bone is characterized by excessive and disordered bone formation, with focal thickening of trabecular and cortical bone. Features include bone pain, fractures, and arthritis of adjacent joints. However, it is uncommon at age <50, and this patient's inflammatory back pain is more consistent with AS. (Choice D) Intervertebral disc protrusion and thickening of the ligamentum flava can lead to spinal stenosis. The pain in this disorder typically radiates to the posterior thighs and legs and is relieved by sitting and flexion of the spine, not activity. Spinal stenosis is usually seen at age >60 and ESR is normal. (Choice E) Multiple myeloma is characterized by plasmacytic infiltrates in the bone marrow. Patients often have back pain at night and during rest, but stiffness is less prominent. Multiple myeloma is uncommon before age 50. Educational objective: Ankylosing spondylitis is an inflammatory spondyloarthropathy characterized by simultaneous erosion of bone and new bone formation. Bone erosions occur primarily in vertebral bodies; however, new bone formation typically occurs at the junction of the periosteal margin and adjacent cartilage, leading to bridging syndesmophytes and ankylosis. This causes spinal rigidity, postural alterations, and increased risk of fracture. __________ References: Syndesmophyte growth in ankylosing spondylitis. (http://www.ncbi.nlm.nih.gov/pubmed/26002023)

A 38-Year-Old Man Is Evaluated Due to a 2-Year History