Internal-Medicine

236 11: Immunology and Allergy
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.
(Kasper, pp. 1560, 1676–1677)
9. (C) 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. (Kasper, pp. 1680–1681)
10. (E) 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.
(Kasper, pp. 1949–1950)
11. (C) 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. (Kasper, pp. 319, 2013)
12. (E) 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. (Kasper, pp. 1940–1941)
13. (E) 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.
(Kasper, pp. 1949–1950)
14. (D) 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.
(Kasper, pp. 1951–1953)
15. (D) 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. (Kasper, p. 1951)
16. (E) 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. (Kasper,
pp. 1949–1950)
17. (D) 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