Page 471 - Clinical Immunology_ Principles and Practice ( PDFDrive )

452 ParT FOur Immunological Deficiencies

General screening of immunity
History 1. CBC, differential, platelets Physical examination
1. Number, type, course of infection 2. IgG, IgA, IgM, IgE levels 1. Growth and development
2. Family history 3. Baseline antibody titers: 2. Associated abnormalities
3. Age of onset, sex To immunizations (i.e., DiGeorge facies, rash, telangiectasia)
4. Environmental exposure to infection (e.g., tetanus, pneumococcus) 3. Presence or absence of lymphoid tissue
Isohemagglutinins

Suspicious finding Suspicious finding Suspicious finding
or red flag or red flag or red flag

Disease-specific testing of the immune system
FIG 32.1 Evaluation of Immunity in a Patient for Immunodeficiency Starts With a Careful
History and Physical Examination. Clues in the history for further evaluation include an excess
of respiratory tract infections, of unusual severity; life-threatening infections; infections with
unusual organisms; a family history of immunodeficiency. The outlined laboratory tests provide
an adequate screen of immunity in a patient with no specific findings.

immune defects, such as impairments in phagocyte function exposure to indoor allergens, such as dust mites and molds, often
other than oxidative burst deficiency. The medical history and worsens mucosal congestion and increases the risk of sinusitis
initial laboratory testing often provide clues that suggest a specific and otitis media.
immune disorder, and the examination of specific component
of the immune response or a diagnostic test for specific Immunization and Previous Infections
immunodeficiencies may be indicated. For example, an increased The immunization history provides significant clues, since the
frequency of infections affecting only the respiratory tract and efficacy of vaccines depends on intact immunity. An incom-
caused by encapsulated bacteria direct the exploration to defects plete schedule of immunizations easily explains the incidence
in humoral immunity and complement; in contrast, a history of preventable diseases. A history of an adverse reaction to a
of Aspergillus pneumonia would suggest neutropenia and CGD. live viral vaccine is suspicious for immunodeficiency, as infants
According to the severity of the illness, clinical immunologists with T-cell defects, B-cell defects, and combined T- and B-cell
may recommend an initial exploration of the major components defects are susceptible to potentially fatal or severe infections
of the immune system: lymphocyte subset distribution, antibody from live attenuated vaccines. These infections include measles
responses, T-cell function, phagocyte oxidative burst, and the and chicken pox pneumonitis, rotavirus vaccine-induced diar-
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complement system. rhea, and lymphadenitis caused by the Bacille Calmette-Guérin
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(BCG) vaccine. Historical information regarding the frequency,
EXPLORING THE MEDICAL HISTORY type, and severity of illnesses and infections should be sought.
Individuals with immunodeficiency may have infections with
Age and Environment unusually prolonged courses or unusual severity or that may
The differential diagnosis of immunodeficiency varies with the age present as unexpected complications (Fig. 32.2). Recurrent infec-
of onset of symptoms. Pediatric patients are more likely to present tions that involve multiple sites are more suspicious for immune
a PID than a secondary immunodeficiency. Infants from birth to deficiency than those involving a single site. Also suggestive of
3 months of age have maternal Igs acquired through the placenta, immune compromise are severe and invasive infections, such
unless they were born prematurely. Therefore deficiencies in the as recurrent pneumonia, meningitis, sepsis, septic arthritis,
immune system at this age presenting with frequent infections osteomyelitis, or abscess and infections with organisms of low
most probably result from severe deficiencies in other immune pathogenicity in normal individuals, such as Candida albicans
components, such as neutrophils, complement components, or T or Pneumocystis jiroveci (Table 32.1) Patients with antibody
cells. Older patients might present with increased risk of infections deficiency disorders tend to present with infections caused by
secondary to comorbid conditions, such as allergic inflammation extracellular pyogenic organisms, such as Haemophilus spp.,
or diabetes mellitus, or to a normal decline of immune responses, a Pneumococcus spp., and Streptococcus spp. In contrast, patients
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process known as immunosenescence (Chapter 38). Environmental with defects in cell-mediated immunity are more likely to also
conditions can influence the risk of infection. Infants frequently present with recurrent infections with viruses, fungi, protozoa,
exposed to other infants with infections, such as in the setting of and mycobacteria. Furthermore, infections by catalase-positive
a daycare facility, have more infectious illnesses compared with bacteria, such as Serratia marcescens, may indicate a possible
those who are not exposed. By inducing an inflammatory response neutrophil oxidative burst defect. Recurrent neisserial infections
of the respiratory mucosa, passive cigarette smoke inhalation also may be found in individuals deficient in the terminal complement
predisposes to infections, including otitis media, pneumonia, and components. A relatively normal incidence of infections followed
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bronchitis. The hygiene practices of the patient, caregivers, and by a sudden occurrence of repeated infections in an adult or
family members have an impact on the frequency of infections, adolescent suggests a secondary immunodeficiency, including
such as impetigo and furunculosis. For patients with allergies, HIV infection.