Psoriasis is characterized by:

A. Asthma is incorrect because asthma is a chronic inflammatory disorder of the airways characterized by bronchospasm, airway hyperreactivity, and mucus production, leading to wheezing, shortness of breath, and cough. It does not involve alveolar filling with fluid or exudate, so gas exchange is not directly impaired in the same way as pneumonia.

B. Emphysema is incorrect because emphysema is a chronic obstructive pulmonary disease (COPD) in which alveolar walls are destroyed, causing enlarged air spaces and reduced surface area for gas exchange. While gas exchange is impaired, emphysema is not an acute infection and does not present with fever or productive cough from alveolar exudate.

C. Sinusitis is incorrect because sinusitis is an infection or inflammation of the paranasal sinuses, leading to facial pain, nasal congestion, and purulent nasal discharge. It does not directly affect the alveoli or oxygen-carbon dioxide exchange in the lungs.

D. Pneumonia is correct because pneumonia is an infection of the lungs in which the alveoli become filled with fluid, pus, or cellular debris due to bacterial, viral, fungal, or other infectious agents. This alveolar filling impairs oxygen-carbon dioxide exchange, resulting in dyspnea, productive cough (often with sputum), fever, chills, and chest pain. Pneumonia can be community-acquired or hospital-acquired, and severity ranges from mild to life-threatening depending on the pathogen and the patient’s immune status.

A. Western European is incorrect because sickle cell anemia is rare among individuals of Western European descent. While carriers exist, the prevalence is much lower than in populations of African ancestry.

B. Native American is incorrect because sickle cell anemia is uncommon in Native American populations. Other hemoglobinopathies, like thalassemia, may be more prevalent in specific indigenous groups.

C. African is correct because sickle cell anemia is caused by a recessive mutation in the HBB gene, which affects the beta chain of hemoglobin. This mutation leads to the production of abnormal hemoglobin S, causing red blood cells to adopt a sickle shape under low oxygen conditions. Sickle-shaped cells are rigid, sticky, and prone to hemolysis, leading to anemia, vaso-occlusive crises, and organ damage. The gene is more commonly found in individuals of African descent, as heterozygosity (carriers) provides some protection against malaria, which historically explains the high prevalence in Africa.

D. Asian is incorrect because sickle cell anemia is relatively rare in Asian populations. Other hemoglobin disorders, such as thalassemia, are more common in Southeast Asian and Mediterranean populations.