A 29-year-old woman is being treated with penicillin for “strep throat.” She develops arthralgia, lymphadenopathy, urticaria, and an active urine sediment 6 days after starting the antibiotics. Which of the following is the most likely mechanism of this drug reaction?
Drug hypersensitivity is the most common cause of serum sickness. It is believed that the drug acts as a hapten binding to a plasma protein. The resultant drug-protein complex induces an immune response. Common signs and symptoms include fever, skin rash (urticarial or morbilliform), arthralgias, lymphadenopathy, and albuminuria. Arthritis, nephritis, neuropathy, and vasculitis are less common. Primary sensitization requires 1–3 weeks, but symptoms can occur rapidly on reexposure
A 24-year-old man is diagnosed with disseminated histoplasmosis after developing symptoms of fever, lymphadenopathy, hepatosplenomegaly, and pancytopenia. Which of the following is the body’s major immunologic defense against histoplasmosis?
The major reaction to fungal infections such as histoplasmosis is delayed-type hypersensitivity. This is a reaction of T cells, which have been stimulated by antigen to react against infectious agents, grafts, and tumors. A classic example is the response to the tuberculin skin test in a person previously exposed to Mycobacterium tuberculosis organisms which occurs between 48 and 72 hours after antigen exposure.
Which of the following are large, granular lymphoid cells that are mediators of antibodydependent cellular cytotoxicity?
NK cells may be of T-cell lineage or monocyte-macrophage lineage. They appear to play an important role in surveillance mechanisms.
A 9-year-old boy presents with sneezing, runny nose, and nasal congestion. The symptoms are seasonal and worse in the spring time. He is diagnosed with hay fever (allergic rhinitis). Which of the following statements about hay fever is correct?
Allergic asthma is often associated with a personal and/or family history of allergic diseases. It is dependent on an IgE response controlled by T and B lymphocytes and activated when antigens interact with mast cell-bound IgE molecules. Most provoking allergens are airborne. Allergic asthma can be seasonal.
A 19-year-old man has recurrent attacks of gastrointestinal colic and swelling of his face and legs. There is no relationship of the attacks to any foods or activity. His father has a similar syndrome. Which of the following is the most likely cause of death in this disease?
Hereditary angioedema is an autosomal dominant condition. The lesions are tense, rounded, nonpitting, and several centimeters in diameter. The edema, unlike urticaria, involves deeper tissue and is not pruritic. Edema of the glottis is the usual cause of death.
A 34-year-old woman with human immunodeficiency virus (HIV) has a routine complete blood count performed. She was diagnosed 2 years ago, and is currently doing well with no symptoms and not on any antiretroviral therapy. Which of the following changes is most likely seen on her peripheral blood cell counts?
Acquired immune deficiency syndrome (AIDS) is characterized by lymphopenia, with a selective diminution of helper T cells. Likely infectious complications and their appropriate prophylaxis can be predicted by the CD4 Tlymphocyte count. Lymphocyte dysfunction can occur even when severe lymphopenia is not yet present.
A 30-year-old woman with myasthenia gravis is found to have an autoimmune hemolytic anemia. The chest x-ray (CXR) reveals an anterior mediastinal mass. Which of the following is the most likely diagnosis?
Thymic tumors may be associated with myasthenia gravis, red cell aplasia, polymyositis, hemolytic anemia, pemphigus, and agranulocytosis. There is also an association with immunodeficiency and thymoma. These patients have B-lymphocyte deficiency and bacterial infections and diarrhea. Erythroid aplasia may develop as well.
A 19-year-old man presents with coughing up blood and decreased urine output. On examination, he has normal air entry, and heart sounds. There is no skin rash or lymph nodes and his abdomen is normal. CXR reveals patchy infiltrates in both lower lobes and his creatinine is elevated. Urinalysis is positive for red cells and protein. A renal biopsy reveals autoantibodies to basement membranes. Which of the following is the most likely diagnosis?
Autoantibodies can be demonstrated by immunofluorescence or electron microscopy on the basement membranes of glomeruli and alveoli in Goodpasture’s syndrome. The disease is most common in young men but can strike at any age. The hemoptysis can be minimal or massive. The course of the hemoptysis is variable, but renal involvement is often progressive. Current therapy includes intensive plasma exchange, cytotoxic agents, and glucocorticoids. Other causes of lung-renal syndromes such as various vasculitides, Wegener’s granulomatosis, mixed essential cryoglobulinemia, Henoch-Schönlein purpura, and systemic lupus erythematosus (SLE) are not characterized by antibodies to basement membranes.
A 25-year-old woman presents with decreased urine output, new leg edema, and facial swelling. She was previously well with no past medical history. Laboratory investigations reveal acute renal failure and a renal biopsy is performed. Immunofluorescence of the biopsy specimen reveals a granular pattern of immune complex-mediated glomerulonephritis. Which of the following conditions is most likely to cause this pattern of renal injury?
Immune complexes are not detected in ATN, Wegener’s, HUS, or Goodpasture’s syndrome. Immune complexes with low complement levels can be seen in idiopathic and postinfectious glomerulonephritis, lupus, cryoglobulinemia, shunt nephritis, and bacterial endocarditis. Immune complexes with normal complement levels are found in IgA nephropathy and Henoch-Schönlein purpura.
A 25-year-old woman has been getting desensitization shots for an allergy for 1 year. Today she developed diffuse urticaria 5 minutes after the injection. Which of the following is the most appropriate next step in management?
These systemic reactions are uncommon and easily managed in the office if detected, but if the patient leaves too soon, it could be dangerous. The exact mechanism of benefit for hyposensitization therapy is unclear. No single measurement of immune function correlates well with clinical efficacy, suggesting a complex of effects that likely includes a reduction in T-cell cytokine production. This type of therapy is reserved for clearly seasonal diseases that cannot be adequately managed with drugs.
A 23-year-old man treated for strep throat with penicillin develops arthralgia, urticaria, and lymphadenopathy. Urinalysis reveals red cell casts. Which of the following is characteristic of the syndrome?
The symptoms of serum sickness are usually self-limited and may recur after apparent recovery. The natural course is 1–3 weeks. Recurrence can occur rapidly (12–36 hours) if repeat exposure to the offending antigen occurs.
A22-year-old woman has recurrent fungal infections and is suspected of having immunodeficiency secondary to impaired T-cell function. Which of the following is the most cost-effective screening test of cellular immunity?
A positive skin test with C. albicans extract (erythema and induration of 10 mm or more at 48 hours) excludes virtually all primary T-cell defects. Lymphocyte enumeration and responses to mitogens are much costlier tests. Serum IgA levels are a good screening test for agammaglobulinemia, and the nitroblue tetrazolium assay is useful to detect killing defects of phagocyte cells.
A 19-year-old female university student unwittingly eats shrimp in the dormitory dining room. Over the next 20 minutes, acute skin lesions consisting of erythematous, elevated wheals appear. Which of the following is most characteristic of these lesions? (See Fig. 11–2.)
Although urticaria can involve any epidermal or mucosal surface, the palms and soles are usually spared. The associated itching indicates stimulation of nociceptive nerves. The increased blood flow results in erythema that blanches on pressure. An ongoing, immediate hypersensitivity reaction in association with degranulation of mast cells is the most common cause.
A 27-year-old man develops small (several millimeters) pruritic wheals when he goes jogging and when he takes very hot showers. Which of the following is most appropriate in the management of this condition?
This represents a case of generalized heat urticaria or cholinergic urticaria rather than exercise-induced urticaria. The latter is characterized by larger lesions and possible anaphylactic reactions and is not triggered by hot showers. Although thought to be cholinergically mediated, atropine does not block symptoms in generalized heat urticaria. Because anaphylaxis does not occur and hydroxyzine is so effective, hot showers are not a great danger
A 42-year-old man has an allergy to penicillin. He is given cephalexin for a skin infection on his finger after a cut became infected. He now develops angioedema after drug exposure. Which of the following physical findings is characteristic of this syndrome?
Angioedema is often not itchy and, like urticaria, is transient; manifestation peaks in minutes to hours and disappears over hours to days. The fluid extravasates from deeper areas such as dermal and subdermal sites. Unlike other causes of edema, angioedema is not dependent and can involve all epidermal and submucosal surfaces, although the lips, tongue, eyelids, genitalia, hands, and feet are the most commonly involved.
A 47-year-old woman, with Type I diabetes of 30 years’ duration, is in the hospital for assessment of atypical chest pain. While in the hospital, she develops a true anaphylactic reaction. Which of the following is the most likely cause for the reaction?
Anaphylaxis is characterized by an initial exposure followed by the formation of specific IgE antibody. Repeat exposure results in antigen combining with IgE bound to basophils and mast cells and subsequent degranulation. Anaphylactoid reactions, such as those to radiographic contrast media, are generally not immunemediated and do not require prior exposure. Insulin and folic acid rarely cause anaphylaxis. Similarly, erythromycin is not a common antibiotic to cause anaphylaxis. Nuts, eggs, seafood, and chocolate are among the many foods implicated in anaphylaxis.
A 27-year-old long-time intravenous (IV) drug user has recurrent infections and a low CD4+ count. Which factor is true concerning this immunosuppression?
Even in advanced AIDS, only a minority of CD4+ lymphocytes are actually infected. Numerous other factors, including “innocent bystander destruction” and autoimmune phenomena, might be implicated. Impaired soluble antigen recognition by T lymphocytes can occur when absolute counts are still normal. Polyclonal activation of B cells, which occurs early in the disease, is unlikely to be triggered by direct HIV infection of B cells. Macrophages are felt to be particularly important in carrying the virus across the blood-brain barrier. Circulating immune complexes might help explain arthralgias, myalgias, renal disease, and vasculitis that occur in infected individuals.
A 24-year-old man with known HIV infection presents with a right hemiparesis that developed over several days. Cognitive examination reveals global impairment, and a computed tomography (CT) scan reveals multiple cortical lesions that are spherical and ring enhancing. Which of the following is the most likely diagnosis?
The three most common causes of focal brain lesion in HIV disease are toxoplasmosis, primary central nervous system (CNS) lymphoma, and progressive multifocal leukoencephalopathy (PML). Toxoplasmosis lesions are typically multiple, spherical, and ring-enhancing on CT scan. They are most likely located in the basal ganglia and the cortex. The symptoms develop characteristically over days and global brain dysfunction is common. Lymphoma presents with one or relatively few irregular weakly enhancing lesions more commonly in the periventricular area. PML presents with multiple nonenhancing lesions in the white matter. CMV, herpes, and Cryptococcus generally cause diffuse brain disease. Glioblastoma multiforme is not characteristic of HIV disease.
A 23-year-old woman has had several episodes of severe wheezing over the past 3 years. She is a nonsmoker and feels well in between episodes. She has no personal or family history of atopy. The wheezing episodes are most likely to occur in spring. Which of the following is the most likely mechanism of wheezing in this woman?
There is a constant state of hyperreactivity of the bronchi, during which exposure to an irritant precipitates an asthmatic attack. A following subacute phase has been described that can lead to late complications. The presence of inflammation in the airways has resulted in increased usage of inhaled corticosteroids for maintenance therapy. Many cases of asthma have no discernible allergic component.
A 45-year-old man with severe asthma is doing well after a recent exacerbation requiring hospital admission. He is interested in avoiding any potential agents that might trigger his asthma. Which of the following foods is most likely to precipitate an asthmatic reaction in this man?
Sulfites, used to keep salad greens fresh, can cause severe asthmatic reactions. Other sulfite-containing foods include fresh fruits, potatoes, shellfish, and wine. Aspirin, tartrazine (a coloring agent), and beta-adrenergic agonists also commonly provoke asthmatic attacks.
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