Differential Diagnosis for 80-year-old with New Onset CKD and Red Purpuric Rash
Single most likely diagnosis:
- Henoch-Schönlein Purpura (HSP): This condition is characterized by the deposition of IgA immune complexes, leading to vasculitis, which can cause a purpuric rash, kidney involvement (nephritis), and sometimes gastrointestinal symptoms. The rapid onset of CKD in conjunction with a purpuric rash makes HSP a strong consideration, especially given its potential to affect the kidneys.
Other Likely diagnoses:
- ANCA-associated Vasculitis: Conditions like Granulomatosis with Polyangiitis (GPA) or Microscopic Polyangiitis (MPA) can present with renal involvement and purpura due to small vessel vasculitis. The age and rapid progression of CKD, along with the skin manifestations, could suggest one of these diagnoses.
- Cryoglobulinemic Vasculitis: This condition involves the deposition of cryoglobulins (proteins that precipitate from blood serum at cold temperatures) in blood vessel walls, leading to vasculitis. It can cause skin lesions, including purpura, and renal impairment due to the involvement of small and medium-sized vessels.
Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):
- Thrombotic Thrombocytopenic Purpura (TTP) or Hemolytic Uremic Syndrome (HUS): Although less common, these conditions can present with renal failure and purpura. TTP and HUS are characterized by microangiopathic hemolytic anemia, thrombocytopenia, and renal failure, making prompt diagnosis critical due to their high mortality rates if untreated.
- Malignancy-associated Vasculitis: Certain cancers can trigger vasculitis, which might present with skin purpura and renal dysfunction. Identifying an underlying malignancy is crucial for appropriate management.
Rare diagnoses:
- Goodpasture Syndrome: An autoimmune disease caused by antibodies against the glomerular basement membrane, leading to rapidly progressive glomerulonephritis and sometimes pulmonary hemorrhage. While it can cause renal failure, the presence of a purpuric rash is less common.
- Mixed Cryoglobulinemia associated with Hepatitis C: This condition can lead to vasculitis, affecting the skin and kidneys. Although less common, its consideration is important, especially if there's a history of hepatitis C infection.