A Case of Sarcoidosis in a Patient With IgA Nephropathy

Ayez Khan, MD; Neville Hodges, MD; Mark Lord, MD

Disclosures

March 29, 2005

Discussion

We report this interesting case to provide further evidence of an association between sarcoidosis and IgA nephropathy.[1] There is a lack of any large-scale data in the literature regarding the casual relationship of sarcoidosis and IgA nephropathy.

Sarcoidosis is a systemic disorder that can affect multiple organs. Renal impairment is usually due to an overproduction of 1,25-dihydroxyvitamin D, leading to hypercalciuria with or without hypercalcemia. This can result in nephrocalcinosis and renal failure.[2] The current literature does not indicate that the prevalence of glomerulonephritis is higher in patients with sarcoidosis than in the general population. Some small-scale studies do suggest an association between sarcoidosis and IgA nephropathy.[3]

Berger and Hinglias[4] first described IgA nephropathy in 1968. It is the commonest form of primary glomerulonephritis throughout the world. IgA nephropathy is the most common cause of end-stage renal disease requiring renal replacement therapy.[5]

The relationship between IgA nephropathy and sarcoidosis remains interesting but controversial. Both conditions are systemic disorders with unknown cause. Familial clustering has been reported in both IgA nephropathy and sarcoidosis.[6,7] There is no single gene responsible, but HLA linkage has been suggested strongly for both disorders.[8,9] The immunologic link between the 2 disorders is yet the strongest. There is an increase in the circulating immune complexes, particularly IgA immune complexes in both.[10,11] Of interest, both diseases also share the characteristic of running a benign course in a significant number of patients and a spontaneous remission.

There are reports that suggest that infective factors, such as Mycobacterium tuberculosis[12] and Chlamydophila pneumoniae ,[13] may be implicated in the etiology of sarcoidosis. No such connection has been reported in IgA nephropathy, but it will be interesting to know whether such a connection exists.

It appears that there are environmental, genetic, and immunologic factors either in isolation or in interaction that are responsible for the pathogenesis of IgA nephropathy and sarcoidosis, and these factors may contribute to the common association as well.

Modern techniques, such as whole genome scanning, have shown promising results in the identification of IgA nephropathy and IgA susceptibility genes.[14] It will be interesting to consider these techniques in patients with sarcoidosis. This will help identify not only the risk of the disease, but also provide a better understanding of these disorders and their intriguing association.

The growing evidence and increasing number of cases showing that there is an association between sarcoidosis and IgA nephropathy underline the need for conducting scientific research to try to find out an answer to this question. Meanwhile, it is suggested that this association should be kept in mind while dealing with either of these conditions.

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