Can Chronic Limb-Threatening Ischemia Present Similarly to Cellulitis?
Yes, chronic limb-threatening ischemia (CLTI) frequently coexists with and can mimic cellulitis, making this a critical diagnostic pitfall that demands immediate vascular assessment alongside infection management. 1
The Clinical Overlap Problem
Patients with CLTI and open ischemic ulcers often have associated local infection or cellulitis, creating a confusing clinical picture where both conditions are simultaneously present. 1 This is not merely a diagnostic curiosity—infection (including cellulitis and osteomyelitis) is explicitly listed as a factor that increases demand for blood flow to the microvascular bed, thereby worsening CLI and increasing the risk of limb loss. 1
The ACC/AHA guidelines emphasize that the diagnosis of CLI may be obscured by associated neuropathic conditions, particularly in diabetic patients who may have impaired sensation despite severe ischemia. 1 This means patients can present with what appears to be simple cellulitis—erythema, warmth, swelling—but the underlying driver is critical ischemia with superimposed infection.
Key Distinguishing Features to Identify CLTI
When evaluating a limb that appears to have cellulitis, you must actively look for these ischemic signs:
- Dependent rubor (reddish-purple discoloration when the limb is dependent) that turns to early pallor on elevation 1
- Reduced or absent pulses on systematic examination 1
- Reduced capillary refill 1
- Pain that worsens when supine and improves with dependency—the opposite of typical cellulitis 1, 2
- Exquisitely painful arterial ulcers (in the absence of neuropathy) that are tender to palpation 1
- Objective hemodynamic abnormalities: ABI <0.4, ankle pressure <50 mmHg, toe pressure <30 mmHg, or TcPO₂ <30 mmHg 2, 3
The High-Risk Population
Diabetic patients represent 50-70% of CLTI cases and are particularly prone to this diagnostic confusion because they often present with neuro-ischemic diabetic foot ulcers. 3 These patients may have severe CLTI and tissue loss but no pain due to concomitant neuropathy, making the clinical picture appear more like simple infection than limb-threatening ischemia. 1
The Critical Management Imperative
Systemic antibiotics should be initiated promptly in patients with CLI, skin ulcerations, and evidence of limb infection. 1 However, antibiotics alone will fail if the underlying ischemia is not addressed. The ACC/AHA guidelines state that patients at risk for CLI who develop acute limb symptoms represent potential vascular emergencies and should be assessed immediately and treated by a specialist competent in treating vascular disease. 1
The risk of amputation depends not only on the severity of ischemia but also on the presence of wounds and infection, which is why the WIfI classification system grades all three components (Wound, Ischemia, foot Infection) from 0-3. 3
Practical Clinical Algorithm
When faced with a patient presenting with apparent lower extremity cellulitis:
- Check pulses immediately—if diminished or absent, this is CLTI until proven otherwise 1
- Perform ankle-brachial index testing—ABI <0.4 in non-diabetics or any diabetic with known PAD defines high CLI risk 2
- Assess pain pattern—worse supine, better dependent = ischemic; worse with dependency = venous/infectious 1, 2
- Look for dependent rubor and elevation pallor—pathognomonic for chronic ischemia 1
- Start antibiotics AND obtain urgent vascular consultation—do not delay revascularization assessment 1
The Bottom Line
The ACC/AHA guidelines make clear that infection can both mimic and complicate CLTI, and the two conditions frequently coexist in a dangerous synergy where infection increases metabolic demand in tissue beds already starved for blood flow. 1 Without treatment, CLI leads to major limb amputation within 6 months, making early recognition of ischemia in the setting of apparent cellulitis a limb-saving imperative. 2