Case Study
Anna Sanchez, a 21-year-old nursing student, comes to her nurse practitioner in December with a 5-week history of itchy eyes and nasal congestion with watery nasal discharge. She also complains of a “tickling” cough, especially at night, and she has had episodes of repetitive sneezing. She gets frequent “colds” every spring and fall.
Physical Examination
Vital Signs: Afebrile; respiratory rate, pulse, and blood pressure all normal
Skin: Flaking erythematous rash on the flexor surfaces of both arms
Head, Eyes, Ears, Nose, and Throat: Tender over maxillary sinuses; sclera red and slightly swollen with frequent tearing; outer nares with red irritated skin; internal nares with red, boggy, moist mucosa and one medium-sized polyp on each side; pharynx slightly erythematous with clear postnasal drainage (NOTE: Nasal polyps are common in allergic rhinitis. They are edematous protrusions of the mucosa that are infiltrated with neutrophils, eosinophils, and plasma cells.)
Lungs: Clear to auscultation and percussion
Initial Post: Answer the following questions about Anna Sanchez and her condition.
What evidence suggests that Anna does not have an acute severe infection? Anna’s vital signs are within normal limits, and she is afebrile. She is not exhibiting abnormal heart or respiratory rate.
If Anna has allergic rhinitis, what type of hypersensitivity reaction is involved? Type I hypersensitivity. “ Type I (IgE-mediated) hypersensitivity reactions are mediated by antigen-specific IgE and the products of tissue mast cells3. Most common allergies (e.g., pollen allergies) are type I reactions. In addition, most type I reactions occur against environmental antigens and are therefore allergic. Because of this strong association, many healthcare professionals use the term allergy to indicate only IgE-mediated reactions” (McCance & Huether, 2019).
A skin test indicates that Anna is allergic to cat dander. Two months ago, Anna’s roommate brought home a cat. Why didn’t Anna’s symptoms start when the cat entered the household, rather than 3 weeks later? “In some individuals, exposure to an environmental antigen causes primarily IgE production. Repeated exposure to the antigen usually is required to elicit enough IgE so that the person becomes “sensitized.” IgE has a relatively short life span in the blood because it rapidly binds to very-high-affinity Fc receptors on the plasma membranes of mast cells” (McCance & Huether, 2019). During the early stage of the initial exposure to cat dander, Anna was becoming sensitized to the allergens in the dander. Anna’s B lymphocytes were producing antibodies, which bound to the outer surface of mast cells.
What class of antibodies bind to the mast cells? IgE
What physiological mechanisms caused the redness of Anna’s nasal mucosa? The increased exposure to the cat dander resulted in the cat danger allergens to bind to the IgE antibodies on mast cells. This caused the mast cells to degranulate and release inflammatory mediators. Some of the mediators caused vasodilation, which created the redness.
What mechanisms caused Anna’s clear postnasal drainage? Vasodilation and increased vascular permeability due to inflammatory mediators released by mast cells led to the postnasal drainage in Anna’s case. “Many local type I hypersensitivity reactions have two well-defined phases. The initial phase is characterized by vasodilation, vascular leakage, and, depending on the location, smooth muscle spasm or glandular secretions. These changes usually become evident within 5 to 30 minutes after exposure to the antigen. The late phase occurs 2 to 8 hours later without additional exposure to the antigen. The late phase has more intense infiltration of tissues with eosinophils, neutrophils, basophils, monocytes, and Th cells and tissue destruction in the form of mucosal epithelial cell damage. B, Activation of mast cells leading to degranulation of preformed mediators (primary mediators) and synthesis of newly formed (de novo) mediators (secondary mediators). ECF, Eosinophilic chemotactic factor; Fc, fragment crystallizable; Ig, immunoglobulin; IL, interleukin; NCF, neutrophil chemotactic factor; PAF, platelet-activating factor; Th, T-helper” (McCance & Huether, 2019).
Reference
McCance, K.L. & Huether, S.E. (2019). Cellular biology. In Brashers, V.L. & Rote, N.S. (Eds.),Pathophysiology: The biologic basis for disease in adults and children(8thed.). Elsevier.