QUESTION 65
An 11-month-old male is brought to his pediatrician by his parents. They report that he has been pulling at his ear, what they recognize as probably an ear infection, since he has had otitis media four times before. The pediatrician decides to order laboratory tests to check for a primary immunodeficiency. Laboratory testing reveals very low concentrations of Ig in the blood, with IgG, IgM and IgA being affected. Flow cytometry of the blood reveals no B cells. Of the following, what is the most likely diagnosis?
A. Chronic granulomatous disease
B. Selective IgA deficiency
C. Leukocyte adhesion deficiency
D. X-linked severe combined immunodeficiency
E. X-linked agammaglobulinemia
Answer for Question 65
Answer: E (X-linked agammaglobulinemia)
Explanation: X-linked agammaglobulinemia occurs in males and presents after the age of 6 months, once passively transferred maternal antibodies are no longer available. Patients present with recurrent infections with encapsulated bacteria, and can also develop some viral infections. Laboratory testing will reveal very low concentrations of immunoglobulin and absence of B cells, since the defect in X-linked agammaglobulinemia prevents the maturation of B cells from pre-B cells. Chronic granulomatous disease affects the ability of white blood cells to make activated oxygen compounds for the killing of bacteria; in many cases it is also X-linked and would be present in males, but the diagnosis is usually made in early childhood. Selective IgA deficiency involves only a deficiency of IgA and presents later in life. Leukocyte adhesion deficiency involves a protein that enables neutrophils to adhere to the endothelium. Symptoms begin in infancy, and at birth, delayed detachment of the umbilical cord can occur, but the disease would not cause low concentrations of immunoglobulin, or absence of B cells. In X-linked severe combined immunodeficiency, most patients present at less than 6 months, with failure to thrive due to disseminated infections such as candidiasis and Pneumocystis. Laboratory testing would reveal decreased T cells. The number of B cells can be normal or increased.
QUESTION 66
A 14-month old male is brought to the pediatrician by his parents because he has been coughing up a thick green mucous. A chest x-ray reveals consolidation of the lower lobe of the right lung. Three months ago, he had an episode of otitis media and seven months ago, he had been diagnosed with Haemophilus influenzae pneumonia. Flow cytometry of the blood reveals an absence of B cells. Of the following, which is he most likely to develop in the future?
A. Disseminated Candidiasis
B. Infectious mononucleosis due to Epstein-Barr virus
C. Giardia lamblia induced diarrhea
D. Aspergillus pneumonia
E. Mycobacterium tuberculosis pneumonia
Answer for Question 66
Answer: C (Giardia lamblia induced diarrhea)
Explanation: given that the patient is male and greater than 6 months of age, and presenting with recurrent bacterial infections of the lung and ear, including with an encapsulated organism (Haemophilus influenzae), and with the laboratory testing revealing an absence of B cells, the clinical presentation would be consistent with a diagnosis of X-linked agammaglobulinemia. Patients with X-linked agammaglobulinemia are most susceptible to infections with encapsulated bacterial organisms (Streptococcus pneumoniae, Haemophilus influenzae, Pseudomonas aeruginosa, Neisseria meningitidis), GI parasites (Giardia and Cryptosporidium) due to lack of IgA, and enteroviruses (which enter the body through the gastrointestinal tract). Infection with Epstein-Barr virus requires the presence of B cells.
QUESTION 67
A 23-year-old female is in a motor vehicle accident and fractures her femur. At the hospital, she requires a blood transfusion in the emergency room, prior to surgery. Her only past medical history is recurrent sinusitis and a past skiing accident that caused a significant laceration, with blood loss requiring transfusion. After receiving the transfusion for the femoral fracture, she develops shortness of breath and requires intubation to protect her airway. Of the following, what is her most likely underlying diagnosis?
A. X-linked agammaglobulinemia
B. Severe combined immunodeficiency
C. Ataxia-telangiectasia
D. Selective IgA deficiency
E. Wiskott-Aldrich syndrome
Answer for Question 67
Answer: D (Selective IgA deficiency)
Explanation: given the past history of sinusitis and the age of the patient, selective IgA deficiency is the best choice. In patients with selective IgA deficiency, transfusion with blood can lead to the development of anti-IgA antibodies, which, when transfused again, can lead to an anaphylactic reaction. X-linked agammaglobulinemia as well as Wiskott-Aldrich are X-linked and would not normally present in a female, and Wiskott-Aldrich normally presents in infants. Severe combined immunodeficiency would present in infancy and, while ataxia-telangiectasia is autosomal recessive and can present in females and at a later age, her past medical history does not include mention of ataxia or telangiectasias.
QUESTION 68
Over the past seven hunting seasons, a 35-year-old male has twice developed Giardia lamblia. Although he admits to routinely drinking water from streams when hunting, his physician decides to order some laboratory tests to evaluate his condition. His past medical history is significant only for the recent development of rheumatoid arthritis. He is up-to-date on his vaccinations, and post-hepatitis vaccination testing revealed normal development of protective antibodies. Laboratory testing reveals a significantly decreased concentration of IgA. Of the following, what else would laboratory testing reveal?
A. Normal IgG; Normal IgM
B. Normal IgG; Decreased IgM
C. Normal IgGl Increased IgM
D. Decreased IgG; normal IgM
E. Decreased IgGl decreased IgM
Answer for Question 68
Answer: A (normal IgG; normal IgM)
Explanation: given his age and the fact that he developed two Giardia lamblia infections, which is an intestinal disease process, a selective IgA deficiency is possible, which is confirmed by the laboratory testing. Patients with selective IgA deficiency also are at risk for the development of an autoimmune disease. Given his age and the presence of the autoimmune disorder, a common variable immunodeficiency would also be possible, and with this condition, the IgG concentration could be decreased; however, as the patient mounted an appropriate response to his vaccinations, common variable immunodeficiency is much less likely as these patients usually have a poor response to vaccination. In selective IgA deficiency, the IgG and IgM concentrations will usually be normal.
QUESTION 69
A 17-year-old female has had frequent episodes of otitis media during her lifetime as well as four serious cases of pneumonia, and one episode of Giardia lamblia induced diarrhea. During a follow-up examination after her diarrhea resolved, laboratory testing reveals decreased concentrations of IgG and IgA; however, flow cytometry reveals an increased number of CD19+ cells. Of the following, a biopsy of the gastrointestinal tract is most likely to reveal?
A. Amoeba
B. Hyperplastic follicles
C. Hypoplastic follicles
D. Amyloid deposition
E. Acute colitis
Answer for Question 69
Answer: B (hyperplastic follicles)
Explanation: given the age of the patient and recurrent infections of the sinopulmonary and GI tract, combined with the laboratory testing, the most likely diagnosis is a common variable immunodeficiency, which can present in females and normally presents later in life. In common variable immunodeficiency, the number of B cells is increased; however, no differentiation to plasma cells occurs. B cells can proliferate in response to an infection, so areas that contain B cells (e.g., lymphoid follicles) can be hyperplastic. These patients do not overproduce a protein, so amyloidosis would not be expected.
QUESTION 70
A 6-year-old male is being seen by his pediatrician for a routine follow-up visit. He has had difficulty learning to walk, has had two episodes of pneumonia requiring hospitalization, and recently his parents have noticed small red nodules on his right eyelid and left ear. Laboratory testing reveals a decreased concentration of IgA. Of the following, what is the inheritance pattern for his condition?
A. Autosomal dominant
B. Autosomal recessive
C. Co-dominant
D. X-linked
E. Mitochondrial
Answer for Question 70
Answer: B (autosomal recessive)
Explanation: the child has ataxia-telangiectasia. This disease process often presents after the age of 5 years. His difficulty walking is a manifestation of the ataxia and the small nodules on his eyelid and ear are telangiectasias. Patients often have decreased IgA. Ataxia-telangiectasia is inherited in an autosomal recessive pattern.
QUESTION 71
A 13-year-old female is having surgery to remove CNS lymphoma that was diagnosed after she had a seizure. During her life, she has had difficulty walking and her speech has of lately been slurred, which was not attributed to the cerebral neoplasm. Physical examination prior to the surgery reveals numerous small red nodules on her body, including her eyelids, antecubital fossa, and sides of the neck. Of the following, laboratory testing would reveal an elevated concentration of which substance, which is used for diagnosis of her underlying condition?
A. IgA
B. IgG2
C. Alpha-fetoprotein
D. Alanine aminotransferase
E. Creatinine kinase
Answer for Question 71
Answer: C (Alpha-fetoprotein)
Explanation: the red nodules on her eyelids and skin are telangiectasias, and her difficulty walking and slurred speech are manifestations of ataxia. Patients with ataxia-telangiectasia are at risk for development of neoplasms, especially lymphoid neoplasms. Individuals with ataxia-telangiectasia can have decreased concentrations of IgA and IgG2. An increased concentration of alpha-fetoprotein is used in the diagnosis of ataxia-telangiectasia.
QUESTION 72
A 2-year-old male is seen by his pediatrician for follow-up of his chronic disease process. He receives daily doses of calcium and vitamin D and, shortly after birth, underwent heart surgery to repair his Tetralogy of Fallot. Of the following, what is the location of the deletion causing his condition?
A. 22q11
B. 22q12
C. 21q11
D. 21q12
E. 11q22
F. 11q12
Answer for Question 72
Answer: A (22q11)
Explanation: hypocalcemia and heart defects are characteristic of Tetralogy of Fallot. The disease can be either complete or partial, depending upon the involvement of the immune system. In partial DiGeorge syndrome, patient’s have preserved T cell function, and their hypoparathyroidism can be treated with calcium and vitamin D supplementation. Congenital heart defects can include Tetralogy of Fallot, truncus arteriosus, and atrial or ventricular septal defects. The deletion occurs at 22q11.
QUESTION 73
At 36 hours after birth, a term female infant is noted by her mother to have muscular spasms. A physician orders stat testing for calcium. The calcium concentration is low. Following the resolution of the muscular spasms, an echocardiogram is performed, which reveals a ventricular septal defect, right ventricular hypertrophy, and an incomplete obstruction of the right ventricular outflow tract Flow cytometric analysis of the blood reveals normal numbers of B lymphocytes, but absent T lymphocytes. A lateral chest x-ray would reveal which of the following?
A. Scoliois
B. Thymic aplasia
C. Thymic hyperplasia
D. Consolidation of one lobe of a lung
E. Absence of the aorta
Answer for Question 73
Answer: B (thymic aplasia)
Explanation: hypocalcemic tetany (i.e., the muscle spasms) occurring shortly after birth, in association with hypocalcemia and in the background of Tetralogy of Fallot is consistent with DiGeorge syndrome, with the hypocalcemia being due to parathyroid gland hypoplasia. Patients also have thymic abnormalities, manifested as thymic aplasia and resultant defects in T lymphocyte function, predisposing to infections with viruses, fungi, parasites, and intracellular bacteria. The B cell function is un-disturbed, and thus, patients will have normal numbers of B lymphocytes. Scoliosis is not a characteristic feature of this disease process, and they are most at risk for fungal, parasite, and viral infections. While the aorta can be abnormal (i.e., an interrupted aortic arch), absence of the aorta would be incompatible with life.