Diffuse lung uptake in stress myocardial perfusion scintigraphy with Thallium-201 in a patient with sarcoidosis

Sir,

We present an interesting image of diffuse lung uptake in thallium-201 stress Myocardial perfusion scintigraphy (MPS) in a patient with sarcoidosis with no underlying perfusion defect and/or left ventricular (LV) dysfunction. A 61-year-old male with history of sarcoidosis and hypertension of 3 years duration presented with dyspnea on exertion (NYHA class II). Treadmill stress testing was moderately positive for inducible myocardial ischemia. He subsequently was subjected to exercise stress MPS with thallium-201 using 1 day protocol. MPS showed diffuse tracer uptake in both lungs [Figures 1, 2]. There were no perfusion defects in any segment of the LV myocardium and gated Single photon emission computed tomography (SPECT) images showed good contractility of all the walls of LV myocardium with a post-stress ejection fraction of 63%.

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Figure 1 Summed angular anterior planar images from SPECT imaging show an increased diffuse lung thallium uptake in both the lungs on the post-stress images

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Figure 2 Exercise thallium SPECT images show diffuse thallium uptake in both the lungs in the 3-D maximum intensity projection image. The short-axis, vertical long-axis, and horizontal long-axis views show normal perfusion in all segments of the left ventricular myocardium

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Diffuse lung uptake in myocardial perfusion scintigraphy (MPS) has been reported as a strong predictor of coronary artery disease (CAD) with severe LV dysfunction.[1] The lung/heart ratio has been useful as a prognostic indicator of adverse outcome in CAD patients. However, diffuse lung uptake is also seen in conditions other than severe LV dysfunction and has been reported in chronic smokers and in conditions with increased pulmonary wedge pressure.[23] We present a patient with a prior diagnosis of sarcoidosis with suspected CAD who underwent stress MPS and showed diffuse lung uptake.

Non-ischemic causes of increased pulmonary capillary wedge pressure, such as mitral regurgitation, mitral stenosis, and so on, are also associated with increased pulmonary thallium uptake.[23] This case report presents sarcoidosis as a novel cause of diffuse lung uptake in MPS. Caution must be exercised in reporting lung uptake as an indicator of severe CAD in these patients.