Tubulointerstitial nephritis-induced hypophosphatemic osteomalacia in Sjögren’s syndrome: a case report and review of the literature

Abstract

Sjögren's syndrome (SS) is a chronic autoimmune inflammatory disease that typically affects the salivary and lacrimal glands. Renal involvement is relatively uncommon and may precede other complaints. Tubulointestitial nephritis (TIN) is the most common renal involvement in SS. Osteomalacia occurring as the first manifestation of renal tubular disorder due to SS is very rare. We report a 39-year-old male who presented with polydipsia, polyuria, and multiple bone pain. Bone density test showed severe osteoporosis, and laboratory findings suggested hypokalemia, hypophosphatemia, and vitamin D deficiency, which supported the diagnosis of hypophosphatemic osteomalacia. He had nephrogenic loss of phosphate and potassium, tubular acidification, and concentration dysfunction. And, the diagnosis of chronic TIN was subsequently confirmed by renal biopsy. The patient reported dry mouth and physical examination showed multiple dental caries. Xerophthalmia, abnormal morphology, and function of the salivary glands by sonography and scintigraphy, together with positive anti-SSA and anti-SSB, confirmed the diagnosis of SS. The TIN indicated SS as the underlying cause of osteomalacia. After taking supplements of potassium, phosphate, vitamin D, and sodium bicarbonate for 1 month, bone pain was alleviated and serological potassium and phosphorus were also back to normal. In conclusion, renal involvement in SS may be latent and precede the typical sicca symptoms. Osteomalacia can be the first manifestation of renal disorder due to SS. Therefore, autoantibody investigations as well as the lacrimal and salivary gland examinations for SS should be considered and performed for suspected patients.

Current State of Knowledge on Primary Sjögren’s Syndrome, an Autoimmune Exocrinopathy

“…Tubular involvement can be associated with dysfunction of any part of the renal tubule and can be responsible for polyuropolydypsic syndrome, low molecular weight proteinuria, aminoaciduria, euglycemic glycosuria, acidosis with normal anion gap, hypokalaemia that may be complicated by paralysis or disturbed heart rhythm, hypophosphoremia linked to increased phosphate excretion that may be complicated by osteomalacia, nephrocalcinosis or the formation of recurrent kidney stones [ 228 , 229 ]. More anecdotally, acquired Gitelman or Bartter syndrome has been described, possibly linked to the presence of specific autoantibodies targeting transporters (ie NaCl co-transporter in Gitelman syndrome) [ 228 , 230 ].…”

Biomarkers and Diagnostic Testing for Renal Disease in Sjogren's Syndrome

“…Hypophosphatemia may lead to acquired hypophosphatemic osteomalacia, a disease of bone metabolism which presents with bone pain, weakness and increased susceptibility to fractures. In one review, 38 cases of pSS presenting with osteomalacia were reported (20). Most of these patients developed osteomalacia in the setting of dRTA, although few suffered from Fanconi's syndrome.…”

A loosening prosthesis in a dialysis patient

“…We did not investigate for the presence of renal tubular acidosis (RTA), even if it has been reported to be associated with bone mineral disorders. If release of phosphate and calcium is accelerated with acidosis, it can be employed as a buffer [ 5 ]. RTA can affect the response to calcitriol in bone and also decrease calcium reabsorption, which can occur in long-term osteomalacia.…”