A 27-year-old construction worker presents to the primary care office with the chief complaint of having low back pain for the last four months. He describes the pain as a gradual onset of non-radiating, aching pain that becomes worse with inactivity and at night. He also notes morning stiffness that lasts between 20 to 30 minutes. He says he has suffered from low back for the past eight years but attributed the pain to his job.

This is the first time the patient has sought medical attention for the low back pain. He denies having neurological symptoms and bowel or bladder dysfunction. His past medical history is significant for one episode of knee effusion when he was 25 years old. He states fluid was aspirated from the knee and he never returned for follow-up treatment. The patient is not taking any medication and says he has no allergies to medication. He has smoked two packs of cigarettes every day for the last five years. He denies alcohol use. The family history is significant as his mother has rheumatoid arthritis.

The physical examination reveals a well-developed and well-nourished young male in slight distress. His vital signs include a sitting blood pressure of 122/68, a heart rate of 66 with regular rate and rhythm, and respiration of 14 breaths per minute. He weighs 156 lbs. with clothes. He is 5’ 11” without shoes.
The physical examination of the spine reveals tenderness over the lumbosacral spine and the sacroiliac joints. There is decreased anterior flexion range of motion of the lumbar spine. Deep tendon reflexes are equal bilaterally. He has a negative straight leg raise and sensory testing is intact to light touch bilaterally of the lower extremities.

Radiographs of the lumbosacral spine and sacroiliac joints reveal squaring of the vertebrae and subchorial erosion of the sacroiliac joints.

Which of the following is the most likely diagnosis?
A. Psoriatic arthritis
B. Lumbosacral strain and sprain
C. Ankylosing spondylitis
D. Spinal stenosis

A Closer Look At The Differential Diagnosis
A) Psoriatic arthrits is not the correct answer. Psoriatic arthrits emerges long after or commensurate with cutaneous psoriasis. The condition affects approximately between 5 to 10 percent of patients with psoriasis and psoriasis precedes the onset of arthritis in 80 percent of patients. The onset of psoriatic arthritis usually occurs between 30 to 35 years of age, and affects men and women equally.

The physical examination of patients with this condition may reveal psoriatic nail disease and distal interphalangeal involvment, asymmetric oligoarthropahy symmetirc polyarthropathy, arthritis mutilans and psoritatic spondylitis.

There is an indisious onset of symptoms, usually asymmetric peripheral arthritis with “sausage” appearnce of fingers and toes. There is joint swelling, tenderness, warmth and decreased range of motion. Nail changes include pitting, traverse ridging, onycholysis, keratosis, yellowing and destruction of nails. Sacroiliac joint involvement is common and may be associated with ankylosing spondylitis.

When this condition is diagnosed, one will note an elevated erythrocyte sedimentation and HLA-B27 will be present. Rheumatoid factor may be positive in 10 percent of patients.

Radiographs will reveal osteolysis, distal interphalangeal pencil-in-cup deformity, bony ankylosis, bilateral sacroiliac joint ankylosis and atypical syndesmophytes of the spine.

B. Lumbosacral sprain and strain is incorrect. Lumbosacral sprain and strain is a tearing of muscle fibers or distal ligamentous attachments of the paraspinal muscles, and most often at the iliac crest or lumbar and sacral region.

This condition is often a result of twisting or lifting with predisposing factors to include repetitive movements of lifting, pushing, pulling or bending, a sedentary lifestyle, obesity, poor posture, stress or a loss of flexibility.

The physcial examination of this patient discloses tense, hard, paraspinal, paravertebral muscle spasms of the lumbosacral spine. There may be a possible absence of normal lordotic curve, presence of a list and decreased range of motion of the lumbosacral spine. There is an absence of neurological involvement.
Baseline radiographs may show a degenerative joint or reverse lordotic curve. While magnetic resonance imaging is not indicated for an initial evaluation, it is indicated when symptoms persist with neurologic involvement.

C. Ankylosing spondylitis is the correct answer. Ankylosing spondylitis is a chronic inflammatory disease of joints in axial skeletal and sacroiliac joints. This condition usually affects males more than females and the onset of symptoms is between 15 to 30 years of age.

There is usually a gradual onset of symptoms of that advance in a cephalad direction with periods of diffuse buttock, heel and low back pain, and profound morning stiffness. Symptoms improve durng the day and return in the evening.

The physical examination reveals bilateral sacroiliac tenderness and restricted back motion, which may result in fixed cervical, thoracic or lumbar hyperkyphosis and restriction of chest expansion. The patient may have painless effusions of larger joints and chin-on-chin deformity.

Ankylosing spondylitis is often associated with uveitis, heart disease and pulmonary fibrosis. Neurologic signs result from compression radiculitis or sciatica. Extraskeletal manifestations include aortitis, angina, pericarditis, renal amyloidosis and pulmonary fibrosis.

Diagnostic studes reveal an elevated ESR, a HLA-B27 that is usually positive and a rheumatoid factor that is usually negative. The earliest radiographic changes are in the sacroiliac joints showing subchorial erosion of the sacroiliac joints. Latter changes of the spine show squaring and generalized demineralization of vertebral bodies and progressive ankylosis. The term “bamboo spine” is used to describe these late findings.

D. Spinal stenosis is incorrect. Spinal stenosis is narrowing of the spinal canal or neural foramina, producing nerve root compression, root ischemia, variable back and leg pain. This condition usually affects men twice as often as women and is more common in late middle age.

Spinal stenosis is usually degenerative and results in the loss of disc volume, increased pressure on apophyseal joints and hypertrophy of soft tissue and bony structure. There is a resulting decrease in the diameter of the spinal canal.

This condition can be congenital, idiopathic or developmental. The symptoms include insidious back pain and extremity paresthesia with ambulaiton and extension. The patient may complain of lower extremity pain, “numbness” or “giving way.”

The physicial examination reveals possible pain and sensitivity loss over one or more dermatomes. Testing range of motion of the spine discloses pain with extension. Patients have normal distal pulses but there may be neurologic findings.

Radiographs reveal disc degeneration, facet hypertrophy, flattening of the lordotic curve and subluxation. Obtaining a CT scan and a MRI is standard to assess nerve root entrapment.

Pertinent Treatment Recommendations
The goal in managing ankylosing spondylitis is to preserve motion. Treatment should include NSAIDs (i.e. indomethacin 75 mg, slow-release), rest and physiotherapy to maintain joint movement, control inflammation and maintain posture and mobility.

TNF modulatory agents may be effective to suppress disease activity and improve function. Adjunctive therapy includes intraarticular glucocorticoids for persistent enthesitis and ocular glucocorticoids for uveitis. If deformity progresses quickly, mobilization may be necessary.

Editor’s Note: For related articles, see www.arthritispractitioner.com.