A 48-year-old man dies in a motor vehicle crash. He had a history of intravenous drug use and had recently been released from prison. The patient's other medical conditions included hepatitis C and hypertension. On autopsy, he is found to have a small, fibrotic focus in the upper portion of the lower lobe of the right lung and a calcified right hilar lymph node. These autopsy findings are most consistent with which of the following?

Question

A 48-year-old man dies in a motor vehicle crash.  He had a history of intravenous drug use and had recently been released from prison.  The patient's other medical conditions included hepatitis C and hypertension.  On autopsy, he is found to have a small, fibrotic focus in the upper portion of the lower lobe of the right lung and a calcified right hilar lymph node.  These autopsy findings are most consistent with which of the following?

Quizplus · Accepted Answer

11ec160b_3a22_246d_9249_15ceadb78efd_MD0001_00 Primary infection with Mycobacterium tuberculosis begins with the inhalation of contaminated respiratory droplets into the lower lobe of the lung. Initially, the organism replicates in an unchecked fashion within the alveoli due to virulence factors (eg, cord factor) that prevent bacterial destruction by alveolar macrophages. The pathogen is also carried by infected macrophages through the draining lymphatic system to ipsilateral hilar lymph nodes. These initial areas of infection (lower lobe, ipsilateral hilar lymph node) are collectively referred to as a Ghon complex. After a few weeks, antigen presenting cells display mycobacterial antigens leading to the stimulation of CD4 cells and the subsequent cytokine-mediated activation of macrophages. Activated macrophages control the infection (in >95% of patients) by forming mature phagolysosomes to kill intracellular mycobacteria and by differentiating into cells (eg, epithelioid cells, Langhans giant cells) that wall off extracellular mycobacteria within granulomas. Over time, granulomas become fibrosed and calcified, which reinforces their structure. It also allows areas of primary infection to be visualized on x-ray or gross pathology. A fibrosed and calcified Ghon complex is referred to as a Ranke complex. (Choices A and C) Most patients with primary tuberculosis contain the infection, but those with ineffective immunity (eg, extremes of age, immunosuppression) can develop progressive illness with hematogenous spread to distant areas (eg, Potts disease, meningitis). Widespread, massive hematogenous dissemination can also occur, resulting in innumerable, small, millet seed-like lesions in multiple organs (miliary tuberculosis). (Choices B and E) Primary tuberculosis infections are usually contained within granulomas but not fully eliminated. If the walls of the granuloma weaken, M tuberculosis can escape and cause reactivation (secondary) disease. This is most common in the setting of acquired immunosuppression (eg, HIV, tumor necrosis factor-alpha inhibitors) and usually presents with symptoms (eg, weight loss, cough, fever) and apical cavitary lesions. Educational objective: The Ghon complex describes the two initial sites (lower lobe of lung, ipsilateral hilar lymph node) of primary tuberculosis infection. Over time, these sites become calcified and fibrosed and can be visualized on gross pathology and radiographic imaging (Ranke complex). __________ References: Clinical aspects of adult tuberculosis. (http://www.ncbi.nlm.nih.gov/pubmed/25659379)

A 48-Year-Old Man Dies in a Motor Vehicle Crash