Systemic Lupus Erythematosus (SLE): This autoimmune disease can cause a wide range of symptoms including chest pain due to pleuritis, shortness of breath, bruising due to thrombocytopenia, and joint pains due to arthritis. The combination of these symptoms, especially in a young woman, makes SLE a strong consideration.

Rheumatoid Arthritis (RA): While primarily known for causing joint pain and swelling, RA can also lead to pleurisy (causing chest pain and shortness of breath) and, less commonly, bruising if associated with medication side effects or secondary Sjögren's syndrome.
Antiphospholipid Syndrome (APS): This condition can cause blood clots leading to chest pain (if pulmonary embolism occurs), shortness of breath, and bruising due to thrombocytopenia or vasculitis. Joint pains can also be present.
Vasculitis (e.g., Giant Cell Arteritis, Polyarteritis Nodosa): Various forms of vasculitis can cause a combination of symptoms including chest pain, shortness of breath, bruising (due to skin manifestations), and joint pains.

Pulmonary Embolism (PE): A life-threatening condition that can cause sudden onset of chest pain and shortness of breath. While bruising is not a typical symptom, it could be related to anticoagulant therapy or underlying conditions.
Disseminated Intravascular Coagulation (DIC): A serious disorder in which the proteins responsible for blood clotting become overactive, leading to widespread clotting and bleeding. This could explain chest pain, shortness of breath (if pulmonary embolism occurs), bruising, and potentially joint pains due to hemorrhage.
Acute Coronary Syndrome (ACS): Although more typical presentations include chest pain without the other symptoms, atypical presentations can occur, especially in women or diabetic patients. The presence of shortness of breath could indicate heart failure.

Relapsing Polychondritis: A rare autoimmune disorder that can cause inflammation of cartilage throughout the body, leading to joint pains, and potentially chest pain if the tracheal cartilages are involved. Shortness of breath and bruising are less common but could occur due to secondary complications.
Ehlers-Danlos Syndrome: A group of disorders that affect connective tissues supporting the skin, bones, blood vessels, and many other organs and tissues. While primarily known for skin hyperextensibility and joint hypermobility, some types can lead to significant vascular complications, including aneurysms or rupture, which could explain the chest pain and shortness of breath.
Sickle Cell Disease: In patients with this condition, sickling crises can lead to acute chest syndrome, characterized by chest pain, shortness of breath, and potentially joint pains due to bone infarcts. Bruising could be seen due to thrombocytopenia or splenic sequestration.