HYPERCALCEMIA UNMASKING UNDERLYING MYCOBACTERIUM AVIUM-INTRACELLULARE INFECTION

Abstract

TOPIC: Chest Infections TYPE: Medical Student/Resident Case Reports INTRODUCTION: Common causes of hypercalcemia include malignancy and granulomatous disease; however nontuberculous mycobacteria (NTM) infections are also rarely associated with hypercalcemia. We present a case of hypercalcemia secondary to underlying Mycobacterium avium-intracellulare (MAI) infection in a patient with acquired immunodeficiency syndrome (AIDS). CASE PRESENTATION: A 36-year-old male with recently diagnosed AIDS (CD4 count 17 cell/uL, viral load 52,400 copies/mL at diagnosis) on anti-retroviral therapy (ART) presented with three days of generalized weakness, nausea, vomiting, and poor appetite associated with night sweats, 20-pound weight loss, dyspnea, and non-productive cough. Vital signs were unremarkable, physical exam revealed moderate lower abdominal tenderness with hepatosplenomegaly, and bloodwork was notable for a corrected calcium of 13.1 mg/dL, undetectable parathyroid hormone (PTH) of <1 pg/mL, elevated 1,25-dihydroxyvitamin D to 112 pg/mL, and decreased PTH-related protein of 7 pg/mL. Hypercalcemia was treated with intravenous fluid hydration and pamidronate. Computed Tomography of Chest/Abdomen/Pelvis revealed bulky retroperitoneal and mesenteric adenopathy and splenomegaly, concerning for lymphoma versus paradoxical worsening of existing opportunistic infection secondary to immune reconstitution with the initiation of ART (CD4 70 cell/uL, viral load 42 copies/mL). He underwent diagnostic laparoscopy with mesenteric lymph node biopsy for definitive diagnosis, with both biopsy and acid-fast bacillus (AFB) culture positive for MAI, clinical picture consistent with disseminated infection. He was started on Ethambutol and Azithromycin and discharged with close infectious disease follow-up. DISCUSSION: Many etiologies exist for hypercalcemia, the most notable being malignancy and granulomatous diseases. In patients with AIDS, NTM infection should also be considered in the differential. To date, there have only been eight reported cases of MAI-associated hypercalcemia, making this the ninth case, and the fourth one with hypercalcemia as the presenting symptom [1]. Though the mechanism is not well understood, one theory postulates the involvement of immune reconstitution inflammatory syndrome (IRIS). In newly diagnosed AIDS patients, the restoration of the immune system due to ART to fight off latent infection causes rebound production of interferon-gamma, which enhances granuloma formation to facilitate the eradication of infection. In turn, granulomas produce 1-alpha hydroxylase, leading to increased 1,25-vitamin D and calcium production [2]. CONCLUSIONS: Non-PTH-mediated hypercalcemia is often attributed to malignancy. However further investigation is warranted to rule out opportunistic infections, especially in newly diagnosed cases of AIDS. REFERENCE #1: Ayoubieh H, Alkhalili E. Mycobacterium avium-intracellulare and the unpredictable course of hypercalcemia in an AIDS patient. Braz J Infect Dis. 2017;21(1):116-118. doi:10.1016/j.bjid.2016.08.002 REFERENCE #2: Tsao YT, Wu CC, Chu P. Immune reconstitution syndrome-induced hypercalcemic crisis. Am J Emerg Med. 2011;29(2):244.e3-244.e244006. doi:10.1016/j.ajem.2010.03.013 DISCLOSURES: No relevant relationships by Sudheer Konduru, source=Web Response No relevant relationships by SANA MULLA, source=Web Response No relevant relationships by Mrunal Sharma, source=Web Response No relevant relationships by Vihitha Thota, source=Web Response No relevant relationships by Manaswitha Thota, source=Web Response