We describe a 48-year-old gentleman with a 30 pack-year smoking history who was admitted for refractory hypoglycemia secondary to a suspected insulinoma. Biochemical work up proved positive warranting imaging studies with computed tomography (CT) chest/abdomen/pelvis to look for an underlying insulin-secreting tumor. His complete blood count showed a white blood cell count of 9.9 x 103/muL, hemoglobin of 13.8 g/dL, platelet count of 442 K/muL with an absolute eosinophil count of 0.1 K/muL. Complete metabolic panel revealed a mildly low sodium level and a glucose level of 34 mg/dL but was otherwise unremarkable. His liver functional tests were normal. His insulin level was elevated at 133 mIU/mL, as well as pro-insulin of 46.5 pmol/L, random cortisol of 129.1 mcg/dL, and c-peptide of 9.3 ng/mL. His vitals signs were normal and he was afebrile.
Imaging studies revealed multiple pulmonary nodules, the largest measuring 1.4 cm x 1.2 cm in left lung (Fig. 1). Further serologic work up was negative for fungal and mycobacterial causes of pulmonary nodules as antibodies for histoplasma, aspergillus, coccidioides, and blastomyces were negative by immuno-diffusion and complement fixation. Interferon-gamma release assay for tuberculosis was negative.
A CT guided core needle biopsy of the largest lung mass was done to rule out neoplasm and revealed a necrotic granuloma on microscopy (Fig. 2). This is not pathognomonic for parasitic disease in this case so other infectious etiologies were considered. The specimen was sent for fungal and mycobacterium culture which were negative at 4 and 6 weeks respectively. No sputum cultures or smears were performed on this patient in the acute setting, this is one of the limitations of our workup.
Further inquiry of patient's social history revealed that the patient has three dogs, one of which was ill with fatigue, weight loss, and hair loss. He could not recall whether he had his dogs were treated for heartworm. The patient denied any travel history to suggest tropical disease and granulomatous diseases such as granulomatosis with polyangiitis and sarcoidosis were ruled out based on the appearance of the biopsy and the absence of any systemic signs or symptoms consistent with inflammatory disease. There were no fevers throughout his hospitalization and lab testing for autoimmune disease was not performed during the workup. While there was not a confirmatory test or obvious parasite on biopsy, clinically the patient was diagnosed with an indolent infection secondary to D. immitis.
The patient was still experiencing repetitive, symptomatic episodes of hypoglycemia while on maximum medical therapy and was transferred to a quaternary care center for management of his biochemical insulinoma. The patient was discharged from the other facility without evidence of insulinoma.
CT scan of the thorax showing multiple pulmonary nodules.