Chronic Venous Insufficiency (CVI): This is the most likely diagnosis given the recurrent nature of the cellulitis, which is a common complication of CVI. The condition leads to poor circulation, edema, and increased susceptibility to infections.

Lymphedema: This condition, characterized by the abnormal accumulation of protein-rich fluid in the interstitial tissue, can lead to recurrent cellulitis due to the compromised immune response in the affected limb.
Diabetic Foot Infection: If the patient has diabetes, a diabetic foot infection could be a likely cause, especially if there are any signs of neuropathy or vascular disease.
Stasis Dermatitis: This condition, often associated with CVI, can increase the risk of cellulitis due to the skin's compromised barrier function.

Necrotizing Fasciitis: Although less common, this is a life-threatening condition that requires immediate recognition and treatment. It presents with severe pain, swelling, and signs of systemic toxicity.
Osteomyelitis: Chronic or recurrent infections can lead to bone involvement, which would necessitate a different treatment approach, including the potential for surgical intervention.
Deep Vein Thrombosis (DVT): While DVT itself does not directly cause cellulitis, the two conditions can coexist, especially in the context of CVI, and missing a DVT could have severe consequences.

Factitious Disorder (Munchausen Syndrome): In some cases, recurrent infections might be self-induced, which is a psychiatric condition that needs a multidisciplinary approach for management.
Erythema Elevatum Diutinum: A rare skin condition characterized by recurrent eruptions of red, purple, or brown lesions, often on the extensor surfaces of the limbs, which could be mistaken for cellulitis.
Sickle Cell Disease with Leg Ulcers: Although more common in certain populations, sickle cell disease can lead to leg ulcers that might become infected, presenting similarly to recurrent cellulitis.