Pediatric Examination and Board Review (159 page)

BOOK: Pediatric Examination and Board Review

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9.
(D)
Leukemia relapses most commonly occur in the bone marrow but can also occur in the CSF and testes, both sanctuary sites where chemotherapy penetration is limited by the blood-brain and bloodtestes barriers, respectively. Leukemia relapses can occur in solid organs such as the liver or spleen but are extremely rare.

10.
(C)
Pneumocystis jiroveci
infections are common in patients with malignancies receiving chemotherapy and occur in up to 50% of these patients in the absence of prophylactic therapy.
Pneumocystis jiroveci
pneumonia is characterized by fever, nonproductive cough, tachypnea, hypoxia, and bilateral diffuse interstitial infiltrates seen on chest radiograph. Acute, fulminant
P jiroveci
pneumonia (PJP) is more common in patients with malignancies than in patients with other forms of immunodeficiency in those settings, whereas PJP is a more chronic, indolent infection. Diagnosis of PJP requires either sputum cultures or bronchoalveolar lavage to look for characteristic cysts and trophozoites of
Pneumocystis jiroveci
.

Oral trimethoprim-sulfamethoxazole is the most effective prophylactic agent for
Pneumocystis jiroveci
pneumonia, with a less than 5% failure rate. Side effects of trimethoprim-sulfamethoxazole include neutropenia and skin rashes, which can progress to Stevens-Johnson syndrome. Dapsone and aerosolized pentamidine are secondary options for PJP prophylaxis; each has a 20% failure rate. Intravenous pentamidine has not been demonstrated to be an effective prophylactic regimen but is pressed into action when the other regimens become impractical. Penicillin has no role in PJP prophylaxis. Patients with new diagnoses of hematologic malignancies and all patients receiving chemotherapy should receive some form of prophylactic therapy. Furthermore, prophylaxis should continue for up to 6 months after therapy has finished because the immune system requires several months for full recovery.

11.
(A)
Live virus vaccines such as oral polio vaccine (OPV) and MMR are contraindicated in patients receiving chemotherapy. Varicella vaccine, although also a live virus vaccine, has been shown to be safe and somewhat effective in patients receiving chemotherapy. Furthermore, although other vaccines are not strictly contraindicated, the relative immunodeficiency in patients receiving chemotherapy impedes the development of protective immunity from the vaccine, and so titers must be checked after completion of chemotherapy to determine whether booster immunizations are needed. In general, vaccinations should be withheld during chemotherapy and should be restarted approximately 3-6 months after chemotherapy treatment has been completed.

12.
(D)
Neutropenia is defined as an absolute neutrophil count (ANC) of less than 1500, with the ANC calculated by multiplying the total white blood cell count by the percentage of neutrophils. Mild neutropenia, with an ANC between 1000 and 1500, is associated with an increased risk of bacterial infections; moderate (between 500 and 1000) and severe (<500) neutropenias are associated with much higher risks of infections. Decreased numbers of neutrophils also decrease or eliminate the signs and symptoms associated with infections and inflammation, with decreased or absent pyuria, minimal CSF pleocytosis, normal chest radiographs, and minimal redness or swelling of skin. Fever is often the only sign of infection in these patients and should be treated urgently. Pseudoneutropenia is a condition common in African Americans in the United States, characterized by an ANC of 1000-1500 but with no increased risk of infections. Neutrophils are generally present within the bloodstream or attached to the vascular endothelial surfaces (a process called margination). Neutrophils can be induced to be released from vascular endothelial cell surfaces by treatment with corticosteroids or epinephrine. Pseudoneutropenia is a result of increased margination of neutrophils, and therefore the true neutrophil count is normal and the patient will have normal responses to infections.

13.
(B)
Antibiotic coverage for patients with fevers and neutropenia needs to provide coverage for the most common and the most serious infections. Historically, gram-negative bacterial infections predominated in patients with neutropenia and were frequently fatal. More recently, with the increased use of central venous catheters, there has been a dramatic increase in the prevalence of gram-positive bacterial infections.

Gram-negative infections most commonly arise from endogenous enteric bacteria that can penetrate mucosal barriers as a result of the neutropenia. They are both common and serious and can cause rapid decompensation and death if not treated. Treatment regimens for patients with fever and neutropenia must therefore include broad-spectrum gram-negative coverage. Infections because of
Pseudomonas aeruginosa
are particularly dangerous in neutropenic patients, and any antibiotic regimen used must provide antipseudomonal coverage. For patients with fever and neutropenia, vancomycin, which only covers gram-positive organisms, is therefore not a good option. Gram-positive organisms from endogenous skin flora or enteric flora can also frequently cause infections but are less likely to be rapidly fatal. Targeted gram-positive coverage, eg vancomycin, is generally not provided as initial therapy. The other antibiotics or antibiotic combinations provide adequate gram-negative and grampositive coverage for initial therapy.

14.
(D)
Patients with an ANC less than 500 are most susceptible to infections from endogenous flora, which are prominent in the GI tract and mucous membranes. The neutropenia results in impaired mucosal barrier defenses, allowing for infections to develop. Therefore, the most common infections include skin infections (cellulitis), respiratory infections (upper and lower), and GI infections (oral infections such as stomatitis or gingivitis and rectal infections such as perirectal abscesses). Bacterial meningitis is infrequent among patients with neutropenia, although it can be severe.

15.
(B)
Features of Shwachman-Diamond syndrome include persistent neutropenia with recurrent skin and respiratory bacterial infections, pancreatic insufficiency with malabsorption, failure to thrive, and metaphyseal chondrodysplasia (most commonly at the hips, knees, shoulders, and wrists). Pancreatic insufficiency and recurrent infections generally begin before the patient reaches 10 years of age. Aplastic anemia occurs in up to 25% of cases of Shwachman-Diamond syndrome, as well as short stature, cleft palate, microcephaly, and thrombocytopenia. There is also an associated increased risk of progression to acute leukemia.

16.
(D)
Rectal temperatures and any procedures that involve potential injury to the perirectal tissues, such as administration of rectal contrast, should be avoided in patients with neutropenia because of the risk of mucosal surface disruption and localized or disseminated infection. Other procedures such as peripheral blood sampling and placement of intravenous lines or a lumbar puncture, if performed with sterile technique, are acceptable to perform on patients with neutropenia. Oral procedures such as tooth brushing or throat cultures are also acceptable but should be done carefully to avoid mucosal injury. Extensive dental work, however, should be avoided if possible.

17.
(C)
Urgent management of varicella exposure in a patient receiving chemotherapy is crucial to avoid potentially life-threatening complications associated with active varicella. Primary varicella has a mortality rate of up to 20% in patients receiving chemotherapy, with disseminated varicella affecting the lungs, liver, and CNS. Varicella-naive children who are exposed to varicella while on chemotherapy should receive varicella immune globulin within 72 hours of exposure. In the absence of varicella immune globulin, intravenous immune globulin is used instead. High-dose intravenous acyclovir should also be given for those patients who develop varicella. Ribavirin is not efficacious against varicella and should not be used.

S
UGGESTED
R
EADING

Jeha S. Tumor lysis syndrome.
Semin Hematol.
2001;38(4 suppl 10): 4-8.

Mahoney DH Jr. Acute lymphoblastic leukemia. In: McMillan JA, DeAngelis CD, Feigin RD, et al, eds.
Oski’s Pediatrics
:
Principles and Practice.
4th ed. Philadelphia, PA: Lippincott Williams and Wilkins; 2006.

Mahoney DH Jr. Quantitative granulocyte disorders. In: McMillan JA, DeAngelis CD, Feigin RD, et al, eds.
Oski’s Pediatrics
:
Principles and Practice.
4th ed. Philadelphia, PA: Lippincott Williams and Wilkins; 2006.

Pieters R, Carroll WL. Biology and treatment of acute lymphoblastic leukemia.
Pediatr Clin North Am.
2008;55(1):1-20.

Rubnitz JE, Gibson B, Smith FO. Acute myeloid leukemia.
Pediatr
Clin North Am
. 2008;55(1):21-51.

Viscoli C, Castagnola E. Treatment of febrile neutropenia: what is new?
Curr Opin Infect Dis.
2002;15:377-382.

CASE 92: A 5-YEAR-OLD WITH PETECHIAE

A 5-year-old boy was brought to the emergency department for evaluation of a new rash. The patient awoke this morning covered in “red dots,” according to his mother. He had a “cold” approximately 2 weeks ago but otherwise has been well. He takes no medications and has had no sick contacts. There is no history of toxin ingestion. The family history is noncontributory.

On physical examination, the child is well appearing and afebrile. He has diffuse petechiae covering his face, neck, chest, back, stomach, arms and legs. He also has large bruises on his forearms and upper and lower legs. He has no palpable lymphadenopathy or hepatosplenomegaly.

A complete blood count done in the emergency department is within normal limits except for a platelet count of 8000/μL.

SELECT THE ONE BEST ANSWER

1.
The differential diagnosis for a petechial rash of acute onset includes all of the following except