Acquired Gitelman syndrome in systemic lupus erythematosus–Sjögren’s overlap with lupus nephritis: a rare autoimmune triad

Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder involving multiple organs. Lupus nephritis (LN) is a common manifestation in SLE; however, the coexistence of acquired Gitelman syndrome in an SLE patient with secondary Sjögren’s syndrome (sSS) is exceedingly uncommon and poses diagnostic challenges. We present a 32-year-old female with frothy urine and muscle cramps in her extremities. Examination revealed pallor, periorbital edema, positive Trousseau’s sign and normal blood pressure. Lab investigations revealed nephrotic proteinuria, hypokalaemia, hypomagnesaemia, hypocalcaemia, metabolic alkalosis and anaemia. Endocrine work-up showed hypothyroidism, low vitamin D and secondary hyperparathyroidism. Urinary indices confirmed renal potassium wasting and hypocalciuria. Autoimmune markers were positive for ANA (antinuclear antibody; 4+, coarse speckled), anti-Sm, anti-SSA, anti-SSB, anti-RNP. Renal biopsy revealed Class V LN. Positive Schirmer’s test with SSA/SSB antibodies positivity confirmed sSS. Based on findings of normotension, metabolic alkalosis, hypokalaemia, hypomagnesaemia, hypocalciuria and kaliuresis - Gitelman phenotype was diagnosed. Genetic testing for SLC12A3 mutations were negative and diagnosis of acquired Gitelman syndrome secondary to autoimmune disease made. She was managed with electrolytes replacement, corticosteroids, mycophenolate mofetil, angiotensin-converting enzyme inhibitors, vitamin D, iron and levothyroxine. On follow-up, electrolyte abnormalities resolved. Tacrolimus was added for persistent proteinuria. This case highlights the importance of recognizing acquired renal tubular defects like Gitelman tubulopathy in SLE–Sjögren’s overlap with LN, especially in patients with unexplained electrolyte disturbances.