**5.3 Crescentic glomerulonephritis**

Crescent Glomerulonephrits (GN) has also been frequently reported in patients with sarcoidosis and co-existing ANCA associated vasculitis. ANCA are autoantibodies found in some autoimmune diseases, recognized by their reactivity with cytoplasmic antigens in neutrophils; two groups are recognized: c-ANCA, reacting with proteinase 3, is found in polyangiitis and Churg-Strauss syndrome; p-ANCA, reacting with myeloperoxidase is found in Wegener granulomatosis. Auinger et al described a patient with rapidly progressive glomerulonephritis and hepatosplenomegaly with no prior diagnosis of sarcoidosis whose renal biopsy showed crescentic GN. (Auinger et al 1997) Diagnosis of sarcoidosis was made with raised angiotensin converting enzyme (ACE) levels and both liver and kidney biopsies showing interstitial noncaseating granulomas. Patient was started on high dose steroids with which renal function improved. Subsequently, the patient developed anti- myeloperoxidase (MPO) antibodies. In contrast, Ahuja et al reported a patient with crescentic GN in the setting of Wegener's granulomatosis (WG). (Ahuja et al 1996). Patient responded well to long term oral cyclophosphamide treatment. Subsequently, the patient developed biopsy-confirmed pulmonary sarcoidosis months later. Given such close associations, it is believed that these sarcoidosis and granulomatous vasculitis like WG may have some common mechanisms. See Figure 3.

#### **5.4 Other glomerular diseases**

Rare associations of sarcoidosis with post-infectious GN have also been noted. Michaels et al. described two patients with sarcoidosis : one with recent history of pneumonia and other with elevated antistreptolysin O titres who developed acute renal failure with active urinary sediments and nephrotic range proteinuria (Michaels et al 2000). Biopsies disclosed diffuse endocapillary proliferative GN with hump-like epithelial deposits. Both patients responded well to corticosteroids with resolution of proteinuria and azotemia. Similarly IgA nephropathy (IgAN), coexisting with sarcoidosis is not unusual given the wide prevalence of IgAN. Taylor and Nishiki described a case of IgAN in sarcoidosis typically presenting as nephritic syndrome that responded well to steroids. (Taylor at el 1996 and Nishiki et al 2010) Renal amyloidosis (AA type) has also noted in patients with long standing sarcoidosis with the classical presentation of steroid resistant nephrotic syndrome with slow progression to end stage renal disease. (Tchenio et al. 1996 and Rainfray et al 1988).
