Which clinical finding indicates a sickle-cell vaso-occlusive crisis?

A. Melasma is incorrect because melasma is characterized by dark, hyperpigmented patches on the skin, usually on the face, due to increased melanin production. It is often related to hormonal changes or sun exposure and does not involve a lack of pigmentation or white hair.

B. Vitiligo is incorrect because vitiligo involves patchy loss of skin pigmentation due to autoimmune destruction of melanocytes. Hair may be affected locally in the depigmented patches, but the condition does not typically result in generalized white hair or the reduced eye pigmentation seen in albinism.

C. Albinism is correct because it is a genetic condition characterized by a congenital lack of melanin, resulting in very light or white skin, white or very light hair, and reduced or absent pigmentation in the eyes. This lack of melanin also increases sensitivity to UV radiation and can affect vision.

D. Psoriasis is incorrect because psoriasis is a chronic autoimmune skin condition that causes red, scaly, and inflamed patches of skin. It does not affect hair color or eye pigmentation and is unrelated to melanin production.

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.