Chronic Kidney Disease (CKD) due to Mercury or Heavy Metal Exposure: The history of using fairness creams, which may contain mercury or other heavy metals, is a significant risk factor for CKD. Prolonged exposure to these substances can lead to renal damage and proteinuria.

Hypertension-related Kidney Disease: Hypertension is a common cause of CKD and proteinuria. Given the patient's age, it is likely that he may have undiagnosed or uncontrolled hypertension.
Diabetic Nephropathy: Although not explicitly mentioned, diabetes mellitus is a common cause of proteinuria, and the patient's age puts him at risk for developing type 2 diabetes.
Focal Segmental Glomerulosclerosis (FSGS): This is a common cause of nephrotic syndrome in adults, characterized by proteinuria and often associated with secondary causes such as obesity, hypertension, or viral infections.

Amyloidosis: A condition characterized by the deposition of amyloid proteins in the kidneys, leading to proteinuria. It can be associated with chronic infections, inflammation, or plasma cell dyscrasias.
Multiple Myeloma: A plasma cell dyscrasia that can cause kidney damage and proteinuria due to the production of light chains that are toxic to the kidneys.
Vasculitis (e.g., ANCA-associated vasculitis): Although the absence of active urinary sediments makes this less likely, vasculitis can cause kidney damage and proteinuria, and missing this diagnosis could have severe consequences.

Alport Syndrome: A genetic disorder affecting the type IV collagen in the kidneys, leading to chronic kidney disease and proteinuria. It is less likely given the patient's age and sex.
Light Chain Deposition Disease: A rare condition characterized by the deposition of light chains in the kidneys, leading to proteinuria and kidney damage.
Membranous Nephropathy: An immune-mediated condition causing proteinuria, which can be primary (idiopathic) or secondary to infections, drugs, or systemic diseases.