Differential Diagnosis
- The patient's symptoms of swelling over metacarpophalangial joints, elevated creatinine, and low C3 and C4 levels suggest an underlying autoimmune or inflammatory condition.
Single Most Likely Diagnosis
- Rheumatoid Arthritis (RA): RA is a common autoimmune disorder that causes joint inflammation and swelling, particularly over the metacarpophalangial joints. Elevated creatinine levels may indicate secondary kidney involvement, and low C3 and C4 levels can be seen in RA due to consumption of complement during the inflammatory process.
Other Likely Diagnoses
- Lupus Nephritis: Systemic lupus erythematosus (SLE) can cause joint swelling, kidney damage (elevated creatinine), and low complement levels (C3 and C4). Lupus nephritis is a common complication of SLE that can lead to kidney failure if left untreated.
- Sjögren's Syndrome: This autoimmune disorder can cause joint inflammation, kidney damage, and low complement levels. Although less common than RA or SLE, Sjögren's syndrome should be considered in the differential diagnosis.
- Mixed Connective Tissue Disease: This condition combines features of RA, SLE, and scleroderma, and can cause joint swelling, kidney damage, and low complement levels.
Do Not Miss Diagnoses
- Wegener's Granulomatosis: This rare autoimmune disorder can cause kidney damage, joint inflammation, and low complement levels. Although less common, Wegener's granulomatosis can be life-threatening if left untreated, making it a crucial diagnosis to consider.
- Goodpasture's Syndrome: This rare autoimmune disorder can cause kidney damage, joint inflammation, and low complement levels. Goodpasture's syndrome can be life-threatening if left untreated, making it an essential diagnosis to consider.
Rare Diagnoses
- Cryoglobulinemia: This rare condition involves the formation of abnormal proteins that can cause joint inflammation, kidney damage, and low complement levels.
- Relapsing Polychondritis: This rare autoimmune disorder can cause joint inflammation, kidney damage, and low complement levels, although it is less common than other conditions in the differential diagnosis.