Differential Diagnosis for Right Foot Pain

Single most likely diagnosis

• Peroneal Tendinopathy: Given the location of the pain at the base of the 5th metatarsal and the styloid process, peroneal tendinopathy is a common cause of pain in this area due to the tendons' proximity to these structures. The mild asymmetric prominence of the soft tissues could be indicative of tendon swelling.

Other Likely diagnoses

• Cuboid Syndrome: This condition involves the cuboid bone and surrounding soft tissues, which could cause pain in the lateral aspect of the foot, including the area near the base of the 5th metatarsal.
• Lateral Plantar Fasciitis: Although plantar fasciitis more commonly affects the medial aspect of the heel, lateral plantar fasciitis can cause pain on the outside of the foot, potentially radiating to the area near the 5th metatarsal.
• Stress Fracture (with normal initial imaging): Early stress fractures might not be visible on initial X-rays, and the location at the base of the 5th metatarsal (a common site for stress fractures) makes this a plausible diagnosis, despite the absence of acute bone abnormalities on imaging.

Do Not Miss diagnoses

• Erythromelalgia: A rare condition characterized by burning pain, heat, and redness in the hands and feet. It's crucial to consider due to its potential association with underlying myeloproliferative disorders.
• Osteoid Osteoma: A benign bone tumor that can cause severe pain, often worse at night and relieved by NSAIDs. It might not be immediately visible on plain X-rays, especially if small.
• Infection (e.g., Osteomyelitis or Soft Tissue Infection): Although less likely given the absence of systemic symptoms or significant findings on imaging, infections can present subtly and require prompt diagnosis to prevent serious complications.

Rare diagnoses

• Tarsal Coalition: An abnormal connection between two or more of the tarsal bones in the foot, which can cause pain and stiffness, particularly if it becomes symptomatic in adulthood.
• Ganglion Cyst: A lump or mass that can develop near joints or tendons, potentially causing pain if it presses on nearby structures.
• Neuroma (e.g., Morton's Neuroma): Although more commonly associated with pain between the toes, a neuroma could potentially cause pain that radiates or is referred to the lateral aspect of the foot.