What are local manifestations of infection? Select all that apply.

Rationale:

A. Sickle cell anemia is a monogenic disorder caused by a mutation in the HBB gene, which leads to abnormal hemoglobin S production. It follows a Mendelian autosomal recessive inheritance pattern, meaning a person must inherit two defective alleles (one from each parent) to express the disease. Environmental factors have little influence on whether the disease occurs, although they can affect disease severity.

B. Cystic fibrosis is caused by mutations in the CFTR gene and is also a single-gene autosomal recessive disorder. Disease expression is largely determined by genetics, although certain environmental factors, like respiratory infections, may influence symptoms and progression. It is not considered multifactorial because a single gene mutation is sufficient to cause the disorder.

C. Hemophilia A is an X-linked recessive disorder caused by a mutation in the factor VIII gene. Males are predominantly affected because they have only one X chromosome. This disorder follows a single-gene inheritance pattern, and while environmental factors can influence bleeding risk, the underlying cause is genetic alone.

D. Cleft palate is a classic example of a multifactorial disorder. It results from the interaction of multiple genes and environmental factors. Genetic predisposition may increase risk, but environmental influences—such as maternal smoking, alcohol use, certain medications, or nutritional deficiencies during pregnancy—can trigger or exacerbate the condition. Unlike single-gene disorders, multifactorial conditions do not follow simple Mendelian inheritance and often appear sporadically within families, though they may recur more frequently among relatives.

Rationale:

A. A pustule is a small, elevated lesion filled with pus, which contains white blood cells, bacteria, and cellular debris. Pustules are commonly seen in bacterial infections of the skin, such as impetigo, folliculitis, or acne with secondary bacterial involvement. The presence of pus is a hallmark of bacterial infection and the body’s inflammatory response to microbial invasion.

B. A macule is a flat, discolored area of skin with no elevation or fluid. Examples include freckles or flat moles. Macules are typically associated with pigmentary changes or viral rashes, not bacterial infections.

C. A plaque is a large, slightly elevated, flat-topped lesion, often with scaling, as seen in psoriasis or chronic eczema. Plaques are usually non-infectious and not indicative of bacterial invasion.

D. Urticaria, or hives, presents as raised, itchy, red welts caused by allergic reactions or histamine release. It is not typically caused by bacterial infections.