Dengue-triggered Hemophagocytic lymphohistiocytosis in an adolescent with autoimmune thyroiditis

Abstract

Introduction: Hemophagocytic lymphohistiocytosis (HLH) is a life threatening hyperinflammatory hematological syndrome characterized by cytokine storm and the diagnosis can be missed as it mimics sepsis or multi-organ dysfunction syndrome. Case Report: A 15-year old adolescent girl presented with six-day history of high grade intermittent fever with easy fatigability and dyspnea on exertion. She was found to have severe anemia elsewhere (Hemoglobin- 4 g/dl, normal 11-16.5 g/dl) and referred to our hospital due to persistent fever, tiredness and recurrent vomiting. On examination she was pale and febrile. Her blood investigations revealed moderate anemia, leukopenia and markedly elevated liver transaminases with coagulopathy. Dengue NS1 antigen and IgM antibodies were positive suggestive of acute dengue infection. Further workup revealed markedly elevated serum ferritin (37973 ng/ml, normal 10-120 ng/ml) and lactate dehydrogenase levels (5311 U/L, normal 180-360 U/L). Plasma fibrinogen level was low (164 mg/dl, normal 200-400 mg/dl). Bone marrow biopsy done on day 3 revealed hemophagocytosis. Serum TSH was mildly elevated (6.5 mU/L, normal 3.5-5 mU/L) and anti-thyroid peroxidase (TPO) antibodies (68 IU/ml, normal <5.6 IU/ml) were also significantly elevated. Diagnosis of Hemophagocytic lymphohistiocytosis (HLH) secondary to dengue infection and autoimmune thyroiditis was made. She was treated with dexamethasone 10 mg/m2 /day from day 3 of admission along with supportive treatment. She rapidly improved and her laboratory parameters returned back to normal at 1 week of follow up. Conclusion: Dengue fever with unexplained severe anemia in the absence of bleeding should be evaluated for HLH as timely initiation of treatment will be life saving