Sarcoidosis Masquerading as Renal Failure in a Patient with Diabetes

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Renal involvement, seen in 1/3 of patients with sarcoidosis, most commonly includes interstitial nephritis (IN), hypercalciuria, and acute tubular injury (ATI).¹ Studies from India have shown granulomatous IN to be the most common histology, followed by non-granulomatous IN and glomerulonephritis.^2,3 We report a 47-year-old gentleman with newly detected hypothyroidism and diabetes of 8 years, who presented with complaints of generalized weakness and increased frequency of urination for 1 month. Physical examination was non-contributory, except for bibasal fine crepitations on chest auscultation. Baseline investigations showed anemia (Hb 10.1 g/dL), renal dysfunction (Cr 3.48 mg/dL), hypercalcemia (Ca 14.45 mg/dL), and asymptomatic hypotonic hyponatremia (Na 114 mmol/L, S osm 250.8 mOsm/kg, U osm 136 mOsm/kg, spot U Na 108 mEq/L). Paraprotein workup was negative. He was evaluated for non-diabetic kidney disease. Renal biopsy was reported as diabetic nephropathy class 2a with ATI. Hypercalcemia was attributed as the reason for ATI (U Ca/Cr 0.8 mg/mg). High-resolution computerized tomography (HRCT) of the chest revealed bilateral ground-glass opacification and bilateral hilar lymphadenopathy. Serum ACE (angiotensin converting enzyme) level was found to be significantly elevated (>140 U/L). He subsequently underwent TBLC (transbronchial lung cryobiopsy), which revealed non-caseating granulomas with giant cell reaction, confirming the diagnosis of sarcoidosis [Figure 1]. Persistent hyponatremia was presumed to be multifactorial; uncorrected hypothyroidism, transient syndrome of inappropriate anti-diuresis (SIAD) secondary to pulmonary infection, and recovering ATI. He was managed with hydration, oral prednisolone (0.5 mg/kg/day), and calcitonin nasal spray (100 units/day). On follow-up, his renal parameters, including serum electrolytes, had normalized. Sarcoidosis is often misdiagnosed as tuberculosis, increasing latency in initiating treatment. Early detection and aggressive treatment is needed for timely control of tissue inflammation and reducing long-term morbidity and mortality.

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Figure 1:

Transbronchial lung biopsy showing confluent granulomas with epithelioid cells (arrow) and giant cells (arrow head); no necrosis seen. Ziehl-Neelsen stain and fungal stain were negative, 100x magnification.

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