Trauma or Injury: This is the most common cause of bruises in the arms, resulting from direct blows, falls, or other accidents that cause blood vessels to rupture and leak into the surrounding tissue.

Vitamin Deficiencies: Deficiencies in vitamins like C or K can affect blood vessel integrity and clotting, leading to easy bruising.
Medication Side Effects: Certain medications, such as anticoagulants (e.g., warfarin, aspirin), can increase the risk of bruising by interfering with blood clotting.
Aging Skin: As people age, their skin becomes thinner and less elastic, making it more susceptible to bruising.
Physical Activity: Engaging in sports or activities that involve repetitive strain or impact on the arms can lead to bruising.

Bleeding Disorders: Conditions like hemophilia or von Willebrand disease can cause bruising due to impaired blood clotting. Missing these diagnoses could lead to severe complications.
Cancer: Certain types of cancer, such as leukemia, can cause bruising due to bone marrow suppression or platelet disorders. Early detection is crucial for effective treatment.
Infections: Severe infections, including sepsis, can cause bruising as part of a broader spectrum of symptoms. Prompt recognition and treatment are vital.

Ehlers-Danlos Syndrome: A genetic disorder that affects connective tissue, leading to fragile skin and blood vessels, which can result in easy bruising.
Amyloidosis: A condition characterized by the deposition of abnormal proteins (amyloid) in various tissues, including blood vessels, which can cause bruising.
Scurvy: A disease caused by severe vitamin C deficiency, which can lead to bruising, among other symptoms.