A Case of Autoimmune Polyglandular Syndrome Type 3b Initially Presenting as Generalized Weakness in an Elderly Patient

Introduction: Autoimmune polyglandular syndrome (APS) is a multiorgan genetic autoimmune disease. APS-3B subtype is autoimmune thyroiditis with pernicious anemia. In this case, we will discuss an elderly female patient diagnosed with APS-3B. Case Presentation: A 69-year-old Caucasian female patient with a past medical history of autoimmune thyroiditis presented to the emergency department with a two-month history of generalized weakness and nausea. Associated symptoms included shortness of breath and diarrhea. Review of systems was otherwise unremarkable. Physical exam was positive for depigmented skin macules over the upper extremities. Lab results showed hemoglobin 8.2 [11.7 - 15.5 g/dL], MCV 121[80 - 100 fL], platelets 144,000 [150 - 450 X10E9/L], WBC 1.9 [4.0 - 11.0 X10E9/L], LDH 1153[100 - 235 U/L], TSH 0.28[0.49 - 4.67 uIU/mL], free T4 1.7 [0.61 - 1.60 ng/dL], direct Coombs test negative. Iron saturation 55%, vitamin B12 level <50 [180 - 914 pg/mL], folate >25[>5.8 ng/mL], total bilirubin 2.3 [0.3 - 1.2 mg/dL], haptoglobin <30 [32 - 228 mg/dL], AST 43 [0 - 41 U/L], reticulocyte 1.4%. Blood smear showed absolute neutropenia with flow cytometry unremarkable. Chest x-ray and urinalysis were negative. Immunofixation showed low IgM 44 [45 - 281 mg/dL], low IgG 619 [635 - 1,741 mg/dL]. Intrinsic factor antibodies (IF-Ab) were positive. Hematology reported that hemolytic anemia is less likely given Coombs test was negative. About 1.5% of Vitamin B12 deficiency present with a hemolytic picture due to ineffective erythropoiesis while Coombs test help to differentiate it from autoimmune hemolytic anemia. Diagnosis of pernicious anemia was made and the patient started on vitamin B12 injections. The combination of pernicious anemia, autoimmune thyroiditis, and vitiligo supported the diagnosis of autoimmune APS-3B. There was a normalization of vitamin B12 level and symptomatic improvement on a one-week follow-up. Discussion: The patient was diagnosed with autoimmune thyroiditis in 2014 with positive anti-TPO antibodies and elevated TSH; she required levothyroxine supplementation since diagnosis. Hypothyroidism causes macrocytic anemia, which may delay pernicious anemia diagnosis. APS-3B is associated with HLA-B8 and/or DR3 and DR5. Many studies reported that autoantibodies can be detected before developing symptoms of organ involvement. Thorough family history provides support for autoantibody testing to detect cases of APS-3B earlier. Active surveillance and early diagnosis will help minimize invasive testing such as bone marrow biopsy, so proper history taking is a key factor to early diagnose these conditions. Conclusion: APS-3B is a rare disorder. Diagnosis is difficult hypothyroidism causes macrocytic anemia. Early detection of APS-3B may help to prevent complications that increase the risk of mortality and morbidity, particularly in the elderly population.