What is the appropriate evaluation and management for an 86‑year‑old man with hypertension, hyperlipidemia, obstructive sleep apnea, type 2 diabetes mellitus, osteopenia, a history of colon cancer, gout, and cervical spinal stenosis with myelopathy who presents with new lower‑back pain and a lower‑back rash?

Evaluation and Management of Lower Back Pain with Rash in an 86-Year-Old with Multiple Comorbidities

The combination of lower back pain and a lower back rash in this patient strongly suggests herpes zoster (shingles), which requires immediate clinical evaluation and antiviral therapy if diagnosed within 72 hours of rash onset to prevent postherpetic neuralgia and other complications.

Immediate Clinical Assessment

Primary Concern: Herpes Zoster

• Examine the rash characteristics carefully: Look for unilateral, dermatomal distribution of vesicular lesions on an erythematous base, which is pathognomonic for herpes zoster 1
• The patient's age (86 years) and multiple comorbidities (diabetes, history of cancer) place him at significantly higher risk for herpes zoster and its complications 1
• If herpes zoster is confirmed, initiate antiviral therapy immediately (within 72 hours of rash onset) with valacyclovir 1000mg three times daily for 7 days or famciclovir 500mg three times daily for 7 days 1

Red Flag Assessment for Serious Spinal Pathology

Given this patient's complex history, you must systematically exclude serious underlying conditions:

Cancer-related concerns (highest priority given history of colon cancer):

• History of cancer is the strongest predictor of vertebral metastasis 1
• Assess for unexplained weight loss, failure to improve after 1 month, or new neurologic symptoms 1
• Obtain immediate MRI if cancer recurrence is suspected, as delayed diagnosis of spinal cord compression leads to poorer outcomes 1

Infection concerns:

• Assess for fever, recent infections, or immunosuppression (diabetes increases risk) 1
• Vertebral osteomyelitis or epidural abscess can present with back pain and overlying skin changes 1

Compression fracture risk (very high in this patient):

• Age 86 years with documented osteopenia places him at extremely high risk 1
• Plain radiography is recommended as initial evaluation for possible vertebral compression fracture in patients with osteoporosis history 1

Neurologic deficits:

• Perform focused neurologic examination assessing lower extremity strength, reflexes, and sensory distribution 2, 3
• Assess for urinary retention, fecal incontinence, or saddle anesthesia (cauda equina syndrome) which requires urgent MRI and surgical evaluation 2, 4
• Given his pre-existing cervical myelopathy, distinguish new lumbar symptoms from progression of cervical disease 1

Imaging Strategy

If Herpes Zoster Without Red Flags:

• Do not obtain routine imaging for nonspecific low back pain in the absence of red flags 1
• Reevaluate after 1 month if symptoms persist despite treatment of herpes zoster 1

If Red Flags Present:

Immediate MRI lumbar spine without contrast is indicated for 1, 4:

• Suspected cancer recurrence or metastasis
• Severe or progressive neurologic deficits
• Suspected cauda equina syndrome
• Suspected infection with fever or systemic symptoms

Plain radiography (2 views) is appropriate for 1:

• Initial evaluation of suspected compression fracture given age and osteopenia
• This provides adequate initial assessment while minimizing radiation exposure

If Symptoms Persist Beyond 6-8 Weeks:

• MRI is preferred over CT if radiculopathy symptoms develop (leg pain in dermatomal distribution, positive straight leg raise) 1, 2, 4
• MRI provides superior soft-tissue resolution for evaluating disc herniation, spinal stenosis, and nerve root compression 1, 4

Initial Management Approach

For Presumed Herpes Zoster:

• Initiate antiviral therapy immediately if within 72 hours of rash onset 1
• Provide adequate analgesia with NSAIDs as first-line (if not contraindicated by renal function or cardiovascular disease) 2
• Consider gabapentin or pregabalin for neuropathic pain component 2

For Mechanical Low Back Pain (if herpes zoster excluded):

• NSAIDs are first-line with good evidence for moderate pain relief 2
• Consider adding skeletal muscle relaxant for short-term use (good evidence for acute low back pain) 2
• Advise patient to remain active rather than bed rest, which is more effective for acute low back pain 2
• Apply superficial heat (good evidence for moderate benefits) 2

What NOT to Do:

• Do not order epidural steroid injections for chronic radicular pain—the most recent BMJ guideline provides a strong recommendation AGAINST this intervention 2
• Avoid opioids as first-line therapy; use lowest dose for shortest time only if NSAIDs insufficient 2
• Do not obtain routine MRI in absence of red flags or persistent symptoms beyond 6-8 weeks 1

Follow-Up Timing

• Reevaluate within 2 weeks given his age (>65 years), multiple comorbidities, and higher risk for complications 1
• Earlier reevaluation is appropriate for severe pain, functional deficits, or if red flag symptoms develop 1
• If symptoms persist beyond 1 month without improvement, reassess for red flags and consider imaging 1, 3

Critical Pitfalls to Avoid

• Do not dismiss the rash as incidental—the temporal association with back pain strongly suggests herpes zoster, which requires prompt treatment 1
• Do not delay imaging if red flags emerge, particularly given his cancer history and age 1
• Do not confuse lumbar symptoms with progression of his cervical myelopathy—cervical stenosis with myelopathy typically presents with upper motor neuron signs and gait disturbance, not isolated lower back pain 1, 5
• Do not obtain plain radiographs if high suspicion for cancer or infection exists—proceed directly to MRI for better soft-tissue visualization 1