Differential Diagnosis for Circumferential Bruising of Mid Forearm with Pain

Single Most Likely Diagnosis

• Soft tissue injury: This is the most likely diagnosis given the presentation of circumferential bruising and pain in the mid forearm without a fracture. The mechanism of injury could involve a direct blow or a twisting injury that results in bruising and swelling of the soft tissues.

Other Likely Diagnoses

• Compartment syndrome: Although less common, compartment syndrome is a possible cause of pain and bruising in the forearm, especially if there's increased pressure within the muscle compartments. This condition can occur without a fracture and is characterized by the five Ps: pain, pallor, pulselessness, paresthesia, and paralysis.
• Hematoma: A collection of blood outside of blood vessels could cause bruising and pain. This might occur due to trauma or a bleeding disorder.
• Insect bite or sting: Certain insect bites or stings can cause significant swelling, bruising, and pain, although this would typically be more localized.

Do Not Miss Diagnoses

• Vascular injury: An injury to the arteries or veins of the forearm could lead to bruising and pain. This is a critical diagnosis not to miss because it can lead to significant complications, including limb ischemia or thrombosis.
• Nerve injury: Damage to the nerves in the forearm can cause pain, numbness, and weakness. While not immediately life-threatening, nerve injuries can have significant long-term impacts on function and quality of life.
• Infection: Although less common as an initial presentation, an infection such as cellulitis could cause pain, swelling, and bruising. This diagnosis is crucial not to miss because untreated infections can lead to serious complications.

Rare Diagnoses

• Snake bite: In areas where venomous snakes are common, a snake bite could cause bruising, pain, and swelling. This would be an unusual cause in most regions but is critical to consider in endemic areas.
• Coagulopathy: A disorder of blood clotting could lead to easy bruising and bleeding into soft tissues, causing pain and swelling. This would be a rare cause of forearm bruising but is important to consider, especially in patients with known bleeding disorders.
• Neoplastic processes: Very rarely, a tumor could cause localized pain, swelling, and bruising. This would typically be a diagnosis of exclusion after other more common causes have been ruled out.