Case Presentation: We describe a 54-year-old male with past medical history of sickle cell disease, who initially presented with worsening dyspnea over the span of two weeks. He had no history of fevers, chills, chest pain, or lower extremity edema, but he did report a chronic dry cough for approximately one year. The patient’s oxygenation saturation initially was at 77 percent on room air and improved to the high 80s and low 90s after receiving 4 liters via nasal cannula. Arterial blood gas showed pH of 7.46, pO2 of 58, pCO2 of 37. CT pulmonary angiogram showed diffuse ground-glass densities with mosaic attenuation, which was likely related to developing pneumonitis, and no evidence of pulmonary thromboembolism. He was admitted for presumed pneumonitis and treated with supplemental oxygen and steroids in the hospital. A bronchoscopy was performed which was inconclusive but consistent with mild fibrosis of alveolar tissue. He improved clinically and was discharged. Because the bronchoscopy was non-diagnostic, open lung biopsy was performed, which revealed small-organized pulmonary thromboembolism vascular changes with mild focal nonspecific fibrosis. Approximately two weeks later, the patient presented with similar symptoms of worsening dyspnea and dry cough. A V/Q scan was performed was suspicious for moderate to high probability of pulmonary embolism in the sub-segmental and bilateral upper lobes. Lower extremity Doppler was negative for deep vein thrombosis. The patient was discharged on lifelong anticoagulation with supplemental oxygen as needed. A follow up visit a month later revealed that the patient was doing better in terms of his shortness of breath but still needed supplemental oxygen at home.

Discussion: Although patients with SCD are at higher risk of forming deep vein thrombosis and pulmonary embolism than the general population, the rates of thrombosis are not well established. Even rarer are microvascular thrombi causing pulmonary embolism in SCD patients. Herein lies a difficult diagnostic approach to sickle cell patients, who present with shortness of breath, but otherwise negative workup for venous thromboembolism. A literature search containing the criteria for microvascular thrombosis in sickle cell disease yielded no case reports of such an event. To the best of our knowledge, this is the first case where an established SCD, who never presents with any prior symptoms, was found to have microvascular emboli in the lungs causing his persistent dyspnea.

Conclusions: Our case demonstrates that formation microvascular thrombi in a SCD patient is a likely etiology of shortness of breath even though initial workup for VTE via CTA of the chest was negative. Although CTA has a higher sensitivity for detecting VTE than a V/Q scan, the biopsy of the lungs confirmed that microvascular thrombi were mostly likely the cause of the patient’s symptoms.  We know that the frequencies of venous thromboembolism and pulmonary arterial thrombosis increase among patients with SCD, and microvascular thrombi in situ have only been observed in autopsy examinations of the lung. Our case demonstrates that a CTA of the chest is not definitive in ruling out pulmonary embolism in sickle cell disease patients and if clinical suspicion for VTE is high, further workup is warranted and to determine the proper course of treatment. In this case, the patient did well on lifelong anticoagulation therapy with supplemental oxygen as needed.