Post-streptococcal glomerulonephritis (PSGN): Given the history of bipedal edema, knee pain, and calf pain that spontaneously resolved a month prior, followed by difficulty breathing, PSGN is a strong consideration. The initial symptoms could be indicative of a post-infectious complication affecting the kidneys, which can lead to fluid overload and subsequent respiratory distress.

Acute Rheumatic Fever (ARF): The patient's symptoms of joint pain (knee and calf) and subsequent respiratory issues could also suggest ARF, especially if there was a recent streptococcal infection. ARF can lead to cardiac involvement, which might explain the breathing difficulties.
Nephrotic Syndrome: Although less likely given the spontaneous resolution of edema, nephrotic syndrome could cause edema and potentially lead to respiratory complications if severe.
Infectious Mononucleosis: Given the age of the patient and the potential for respiratory involvement, infectious mononucleosis (caused by Epstein-Barr virus) could be considered, especially if there are other systemic symptoms like fever or lymphadenopathy.

Pulmonary Embolism (PE): Although less common in teenagers, PE is a life-threatening condition that must be considered, especially with symptoms of difficulty breathing. The recent history of leg pain could be indicative of deep vein thrombosis (DVT), a precursor to PE.
Cardiac Tamponade: If there's any suspicion of cardiac involvement (e.g., from ARF or other cardiac conditions), cardiac tamponade must be ruled out due to its high mortality rate if not promptly treated.
Sickle Cell Crisis: If the patient has sickle cell disease, a crisis could explain both the initial pain episodes and the current respiratory distress.

Goodpasture Syndrome: An autoimmune disease that affects the lungs and kidneys, causing bleeding in the lungs and kidney inflammation. It's rare but should be considered in cases of unexplained renal and pulmonary symptoms.
Wegener's Granulomatosis (Granulomatosis with Polyangiitis, GPA): A rare autoimmune disorder that can affect various parts of the body, including the lungs and kidneys, and could potentially explain the patient's symptoms.
Lymphoma: Certain types of lymphoma can cause respiratory and systemic symptoms, although this would be less likely given the acute presentation and the specific pattern of symptoms described.