A 39-year-old homeless man presents to the emergency department for cough and fever. He says that his illness has been worsening over the past 2 weeks. He originally had dyspnea on exertion and now is short of breath at rest. On questioning, he tells you that he lives in a homeless shelter when he can, but he frequently sleeps on the streets. He has used IV drugs (primarily heroin) “on and off” for many years. He denies medical history but the only time he gets medical attention is when he comes to the emergency department for an illness or injury. On review of systems, he complains of fatigue, weight loss, and diarrhea. On examination, he is a thin, disheveled man appearing much older than his stated age. His temperature is 100.5°F (38.0°C), his blood pressure is 100/50 mm Hg, his pulse is 105 beats/min, and his respiratory rate is 24 breaths/min. His initial oxygen saturation is 89% on room air, which comes up to 94% on 4 L of oxygen by nasal cannula. Significant findings on examination include dry mucous membranes, a tachycardic but regular cardiac rhythm, a benign abdomen, and generally wastedappearing extremities. His pulmonary examination is significant for tachypnea and fine crackles bilaterally, but no visible signs of cyanosis. His chest x-ray is read by the radiologist as having diffuse, bilateral, interstitial infiltrates that look like “ground glass.” Answer the following questions What is the most likely cause of this patient’s current pulmonary complaints? ➤ What underlying illness does this patient most likely have?

The most likely cause of this patient’s current pulmonary complaints is pneumonia. Pneumonia is an infection that inflames the air sacs in one or both lungs, causing cough with phlegm or pus, fever, chills, and difficulty breathing. The patient’s symptoms of cough and fever, along with the physical examination findings of tachypnea (rapid breathing) and fine crackles on pulmonary examination, are consistent with pneumonia.

In addition to pneumonia, this patient most likely has an underlying illness called HIV infection. HIV (human immunodeficiency virus) is a virus that attacks the immune system, specifically CD4 cells (T cells), which are crucial for fighting off infections. HIV infection is associated with a wide range of opportunistic infections and diseases, including pneumonia.

There are several important clues in the patient’s history and clinical presentation that suggest HIV infection as the underlying illness. First, the patient is a homeless man who frequently sleeps on the streets and has a history of IV drug use, specifically heroin. Homelessness and drug use are known risk factors for HIV infection. Second, the patient has a history of dyspnea on exertion, fatigue, and weight loss, which are common symptoms seen in individuals with advanced HIV infection. Third, the patient’s physical appearance is consistent with wasting syndrome, which is a common manifestation of late-stage HIV infection characterized by significant weight loss and muscle wasting.

The patient’s temperature of 100.5°F (38.0°C) and the presence of interstitial infiltrates on the chest x-ray further support the diagnosis of HIV-associated pneumonia. HIV-infected individuals are more susceptible to bacterial, viral, and fungal infections due to their compromised immune system. In this case, the diffuse, bilateral, interstitial infiltrates that look like “ground glass” on the chest x-ray are characteristic of interstitial pneumonia, which is commonly seen in individuals with HIV infection.

In order to confirm the diagnosis of HIV infection, further testing would be necessary. HIV testing typically involves an initial screening test, such as an enzyme immunoassay (EIA) or an antigen-antibody combination immunoassay. If the screening test is positive, it is followed by a confirmatory test, such as a Western blot or an HIV-1/HIV-2 differentiation immunoassay. It is important to note that a positive screening test does not definitively confirm the diagnosis of HIV infection, as false positive results can occur. Therefore, a confirmatory test is necessary to rule out false positives.

Once the diagnosis of HIV infection is confirmed, further evaluation and management should be initiated. This may include baseline laboratory tests, such as a complete blood count, CD4 count, HIV viral load, and assessment of other co-infections, such as hepatitis C and syphilis. Antiretroviral therapy (ART) should be initiated as soon as possible to suppress viral replication, improve immune function, and reduce the risk of opportunistic infections. Additionally, prophylaxis for certain opportunistic infections, such as Pneumocystis jirovecii pneumonia (PCP), may be indicated.

In summary, the most likely cause of this patient’s current pulmonary complaints is pneumonia, and the underlying illness he most likely has is HIV infection. The patient’s history of homelessness, IV drug use, symptoms of dyspnea, fatigue, weight loss, and physical examination findings of wasting syndrome and interstitial infiltrates on chest x-ray are all consistent with advanced HIV infection. Prompt HIV testing, further evaluation, and initiation of appropriate management are necessary to confirm the diagnosis and provide appropriate care for the patient.