ASN's Mission

ASN leads the fight to prevent, treat, and cure kidney diseases throughout the world by educating health professionals and scientists, advancing research and innovation, communicating new knowledge, and advocating for the highest quality care for patients.

learn more

Contact ASN

1401 H St, NW, Ste 900, Washington, DC 20005


The Latest on Twitter

Kidney Week

Abstract: SA-PO936

Native Kidney Osseous Metaplasia – Incidental Finding or a Disease to Treat

Session Information

Category: Nephrology Education

  • 1302 Fellows and Residents Case Reports


  • Okechuku, Gyongyi, Baylor College of Medicine, Houston, Texas, United States
  • Shawar, Saed, Baylor College of Medicine, Houston, Texas, United States
  • Yan, Jingyin, None, Houston, Texas, United States

Osseous metaplasia is an atypical phenomenon involving the formation of the bone tissue outside the skeletal system. This pathologic process may occur in sites such as the skin, subcutaneous tissue, and skeletal muscle, occasionally seen in visceral organ like intra-abdominal sites. We describe a case of osseous metaplasia in a native kidney.


We present a 26 year old African American woman with biopsy proven minimal change disease (MCD) at age of 5. Her disease course is significant for been steroid dependent initially with multiple relapses upon steroid taper and partial remissions. She had 3 renal biopsies in childhood. All 3 were consistent with minimal change disease. Her treatment regimen consisted of steroids, cellcept, started after she had side effect from cyclosporine and Lisinopril. She presented to our Nephrology clinic with worsening SOB, orthopnea and PND. Physical examination was significant for fine crackles in lungs, and 3+ bilateral pitting pedal edema. Labs showed serum calcium 8.2, phosphorus 4.1, vitamin D 34, and bicarbonate of 28, BUN of 15 and creatinine of 0.6. Her white cell count was 6.8, with hemoglobin 6.6, Platelets were 113. Her urinalysis was notable for 2+ proteinuria. C3 and C4 were normal. Negative RF; negative ANA; normal serum protein electrophoresis and light chain assay, dsDNA , ANCA were negative . A renal sonogram was unremarkable. A repeat renal biopsy was done findings suggested Minimal change disease. However, we found unmineralized osteoblast within 1 glomerulus.


Osseous metaplasia (OM) pathophysiology is not well known, but many factors have been incriminated including chronic ischemia, trauma, and chronic inflammation. The pathphyisology of this finding is not well understood. Osseous metaplasia has been described in some transplant allograft, and associated with malignacies affecting the kidney, some leukemias and basal cell carcinoma. Ectopic calcifications are different entities. OM is asymptomatic and probably often confounded with ectopic calcifications since their radiological aspects are identical. Treatment usually is watchful waiting approach.