Internal-Medicine

Answers and Explanations
1. (E) 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.
(Kasper, p. 319)
2. (B) 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. (Kasper,
pp. 1179, 1940–1941)
3. (B) NK cells may be of T-cell lineage or
monocyte-macrophage lineage. They appear
to play an important role in surveillance mechanisms.
(Braunwald, pp. 1911–1913)
4. (A) 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.
(Kasper, pp. 1954–1955)
5. (C) 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. (Kasper,
pp. 1951–1953)
6. (B) 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 T-
lymphocyte count. Lymphocyte dysfunction
can occur even when severe lymphopenia is
not yet present. (Kasper, pp. 1104–1105)
7. (A) 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. (Kasper, pp. 2518–2522)
8. (C) 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
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