Persistent Calciphylaxis and Secondary Hyperparathyroidism in End Stage Renal Disease Patient Due to Ectopic Mediastinal Parathyroid Adenoma- A Case Report

Intruducion: Secondary hyperparathyroidism (SHPT) is prevalent in patients with end-stage renal disease (ESRD) with reported prevalence of 90%. SHPT treatment is usually medical. Although 5% ends up with parathyroidectomy. Indications of parathyroidectomy in ESRD patients include persistent elevation of PTH more than 800, Calcyphylaxis, Osteitis Fibrosa Cystica, and persistent anemia. Among these patients who require surgery, 5–20% present with persistent or recurrent disease and require further re-exploration and excision of parathyroid tissue. We present a case of persistent Calciphylaxis and SHPT in ESRD patient despite Parathyroidectomy which prompted diagnosing an ectopic mediastinal parathyroid adenoma. Case Presentation: 49 year-old male with ESRD for 15 years complicated with SHPT, presented due to worsening Caciphylaxis of bilateral lower extremities despite Cinacalcet, IV sodium thiosulfate, and Phosphate binder. Serum Calcium level was 9.0 mg/dl with corrected levels of 10.2 mg/dl, Phosphorus level of 9.3 with Intact PTH level 1,369 pg/ml. Ultrasound of parathyroid glands was normal. Due to failure of medical treatment, He underwent Total parathyridectomy and left arm parathyroid autograft. Intraoperative PTH level went down to 300 (less than 50%). Calciphylaxis never improved. 5 months later, Parathyroid hormone was elevated 1338 pg/ml, Calcium level 6.9 mg/dl and Phosphorus level 10.0 mg/dl. 99mTc-sestamibi parathyroid scan didn’t show any activity in thyroid gland area and no increased uptake at the autograft area. Although it showed a small focus of persistent activity in substernal area suggestive of ectopic parathyroid tissue. Patient was referred for removal of ectopic adenoma. Discussion: Persistent SHPT is identified as the persistence or recurrence of symptoms, lab abnormalities and radiologic findings within 6 months after parathyroidectomy. Pathophysiology of recurrence is not well studied but one theory suggests that in SHPT, altered Calcium-phosphate hemostasis leads to hyperplasia of parathyroid tissue including ectopic and supernumerary tissue. This aforementioned altered hemostasis continues even after parathyroidectomy and cause hyperplasia and hyperfunction of the residual parathyroid tissue left accidentally by seeding within surgical site or implanted autograft or It can present with ectopic adenoma, even if they were undetected prior to or in the first intervention. Ectopic parathyroid tissue is an uncommon etiology of persistent or recurrent secondary hyperparathyroidism, it is reported in many cases where it was missed at initial workup. Prevalence reported up to 14% in patients with persistent SHPT. It is warranted further investigations to look for ectopic parathyroid tissue in patients with ESRD who present with recurrent or persistent secondary hyperparathyroidism after total parathyroidectomy with reimplantation.