The observed prevalence of renal affection in Sjögren's syndrome (Sjs) approaches 2-67 % due partially to variable definitions of kidney affection.
Kidney disease in Sjögren's syndrome (Sjs)
The observed prevalence of renal affection in Sjögren's syndrome (Sjs) approaches👉 2-67 % due partially to variable definitions of kidney affection. Renal disease in Sjs is usually characterizing by chronic interstitial nephritis, observed clinically by a variable but generally mild rise in SCr, benign urinalysis + tubular dysfunction (e.g., distal (type 1) renal tubular acidosis (RTA), nephrogenic diabetes insipidus (DI) & hypokalaemia):
(1) Defective distal acidification seen in up to 25 % of ptns. The observed metabolic acidosis is often mild, but some ptns may present with plasma bicarbonate <10 mEq/L & plasma K+ < 1.5-2 mEq/L due to continuous urinary K+ wasting. Distal RTA can be observed with no or prior to Dgx of Sjs. So, it’s crucial to consider Sjögren's syndrome in adults with otherwise unexplained distal RTA as ttt aiming at immunologic disorder may partially directed to the acidification deficit.
(2) Polyuria & polydipsia due to 👉 nephrogenic DI is also related to tubular dysfunction that’s also, may be seen prior to Sjs Dgx. It’s crucial to exclude Sjs in adults with nephrogenic DI with no history of chronic lithium toxicity or hypercalcemia.
(3) Interstitial nephritis-induced tubular injury > K+ wasting > severe hypokalaemia.
A course of steroids (e.g., prednisone 1 mg/kg/d up to 60 mg/d taped according clinical response) can be given to ptns with severe active interstitial nephritis. For steroid dependent ptns, azathioprine (1-2 mg/kg/d) can be given as a steroid-sparing agent. Progression to ESKD is a rarely seen. Glomerular affection is much less common than interstitial nephritis in Sjs. Membranoproliferative glomerulonephritis (MPGN) & membranous nephropathy (MN) are most seen. Optimal therapy still uncertain.
Ptns with Sjs should be tested for HCV. Kidney affection in Sjs are nonspecific in this disorder; Dgx generally requires a sicca syndrome + abnormal ocular testing + lymphocytic infiltration around salivary glands in biopsy. However, same ocular findings can be observed in sarcoidosis, & sense of dry mouth can be induced by many drugs. Moreover, ptns with IgG4-related disorder may show salivary & lacrimal gland affection, as well as interstitial nephritis. The auto-AB anti-Ro (SSA) & anti-La (SSB) are 👉relatively specific for Sjs, if present, can help confirming Dgx with proper clinical subsets.
Urinalysis: Proteinuria or cellular casts & haematuria. Urogenital disease: bladder malfunction with Sms of interstitial nephritis & gynaecological Sms include vulvovaginal dryness, pruritus, & dyspareunia. Bladder: Women with Sjs may develop dysuria, frequent urination, nocturia, & urgency. In absence of UTI, these Sms can be attributed to interstitial cystitis.
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