Osteomalacia revealing primary Sjogren's syndrome in a Tunisian woman with distal renal tubular acidosis

Introduction: Sjogren's syndrome (SS) is a chronic disorder affecting primarily exocrine glands associated with lymphocytic infiltrates. The most common renal disease in SS is tubulointerstitial nephritis, responsible for renal tubular acidosis (RTA) in 20% of the patients. It is often latent and can be rarely complicated by osteomalacia. Case presentation: A 40 year-old woman with no medical history, was admitted for lower limb weakness and inability to walk for six months. She had a waddling gait and reported pain upon palpation of the bones. No arthritis was found and neuromuscular examination was normal. The serum calcium (2.13 mmol/L), phosphate (0.68 mmol/L), potassium (2.9 mmol/L) and bicarbonate (18 mmol/L) were low while the alkaline phosphate was elevated (200 IU/L). Protein electrophoresis showed a polyclonal hypergammaglobulinemia (40 g/L). Serum 25-hydroxy vitamin D was 8 mu g/L. Urine was alkaline (Ph = 7) and analysis revealed proteinuria (0.1 g/day), phosphaturia (11.9 mmol/day; normal 22-42 mmol/day) and calciuria at 3 mmol/24 h (normal 2.5-6 mmol/24 h). Plain X-ray revealed Looser's zones on the left femoral neck. Whole-body bone scan showed multiple bone cracks in the rib cage, right clavicle and femur suggesting the diagnosis of osteomalacia. During evaluation, the patient reported dryness of the mouth and eyes. Ophthalmologic examination revealed a superficial punctuated keratitis. Antinuclear antibodies, anti-SSA and anti-SSB were positive. Accessory salivary gland biopsy showed lymphocytic infiltration and the diagnosis osteomalacia related to distal RTA secondary to Sjogren's syndrome was retained. The patient received alkalinizing agents, vitamin D and corticosteroids. Outcome was favorable with normalization of kalemia and improvement of walking. (C) 2016 Egyptian Society of Rheumatic Diseases. Publishing services provided by Elsevier B.V.