February 2012 - Hem/Onc - Quiz, Flashcards & Trivia

1. Which of the following symptoms is most suggestive of an esophageal mass?

Early satiety

Liquid phase dysphagia only

Odynophagia with chest pain

Oropharyngeal dysphagia

Solid phase dysphagia progressing to liquid phase dysphagia

Solid phase dysphagia progressing to liquid phase dysphagia is most suggestive of an esophageal mass. This is because the presence of a mass in the esophagus can cause a narrowing or obstruction, making it difficult to swallow solid foods. As the mass grows or progresses, it can further impede the passage of food and lead to difficulty in swallowing liquids as well. This symptom pattern is characteristic of an esophageal mass and should prompt further investigation and evaluation.

Explanation

Solid phase dysphagia progressing to liquid phase dysphagia is most suggestive of an esophageal mass. This is because the presence of a mass in the esophagus can cause a narrowing or obstruction, making it difficult to swallow solid foods. As the mass grows or progresses, it can further impede the passage of food and lead to difficulty in swallowing liquids as well. This symptom pattern is characteristic of an esophageal mass and should prompt further investigation and evaluation.

2. A 58-year-old woman presents to the emergency room complaining of jaundice. She first noticed a yellowish discoloration of her skin about 3 days ago. It has become progressively worse since that time. In association with the development of jaundice, she also has noticed clay-colored stools and pruritus. There has been no associated abdominal pain, fever, chills, or night sweats. She has a past medical history of alcohol abuse, but has been abstinent for the past 10 years. She has no known history of cirrhosis. On physical examination, she is afebrile with normal vital signs. She is jaundiced. The bowel sounds are normal. The abdomen is soft and nontender. There is no distention. The liver span is 12 cm to percussion and is palpable at the right costal margin. The spleen tip is not palpable. Liver function testing reveals an AST of 122 IU/L, ALT of 168 IU/L, alkaline phosphatase of 483 U/L, total bilirubin of 22.1 mg/dL, and direct bilirubin of 19.2 mg/dL. On right upper quadrant ultrasound, the gallbladder cannot be visualized, and there is dilatation of the intrahepatic bile ducts but not the common bile duct. What is the most likely diagnosis?

Cholangiocarcinoma

Cholecystitis

Gallbladder cancer

Hepatocellular carcinoma

Pancreatic cancer

The most likely diagnosis in this patient is cholangiocarcinoma. Cholangiocarcinoma is a malignant tumor that arises from the bile ducts. The patient's presentation with jaundice, clay-colored stools, and pruritus is consistent with obstructive jaundice, which can occur when a tumor blocks the flow of bile. The elevated liver function tests, dilatation of the intrahepatic bile ducts, and inability to visualize the gallbladder on ultrasound further support this diagnosis. Cholecystitis, gallbladder cancer, hepatocellular carcinoma, and pancreatic cancer are less likely given the clinical presentation and findings.

Explanation

The most likely diagnosis in this patient is cholangiocarcinoma. Cholangiocarcinoma is a malignant tumor that arises from the bile ducts. The patient's presentation with jaundice, clay-colored stools, and pruritus is consistent with obstructive jaundice, which can occur when a tumor blocks the flow of bile. The elevated liver function tests, dilatation of the intrahepatic bile ducts, and inability to visualize the gallbladder on ultrasound further support this diagnosis. Cholecystitis, gallbladder cancer, hepatocellular carcinoma, and pancreatic cancer are less likely given the clinical presentation and findings.

3. A patient with acute lymphoid leukemia (ALL) is admitted with respiratory distress and chest pain. The patient reports 1 day of shortness of breath not associated with cough. There have been no sick contacts, and before the onset of the respiratory symptoms, the patient only recalls fatigue. A chest radiograph shows faint diffuse interstitial infiltrates without pulmonary edema. The cardiac silhouette is normal. An arterial blood gas shows a PaO2 = 54 mmHg, while the pulse oximetry is 97% on room air. A carbon monoxide level is normal. All of the following laboratory abnormalities are expected in this patient except:

Bcr-abl mutation

Blast count >100,000

Elevated lactate dehydrogenase levels

Increased blood viscosity

Methemoglobinemia

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Explanation

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4. Which of the following best describes the mechanism of action of clopidogrel?

Activates antithrombin and inhibits clotting enzymes

Binds to the activated GPIIb/IIIa receptor on the platelet surface to block binding of adhesive molecules

Inhibits cyclooxygenase 1 (COX-1) on platelets to decrease production of thromboxane A2

Inhibits phosphodiesterase to block the breakdown of cyclic adenosine monophosphate (cAMP) to inhibit platelet activation

Irreversibly blocks P2Y12 to prevent adenosine diphosphate (ADP)–induced platelet aggregation

Clopidogrel irreversibly blocks the P2Y12 receptor, which is responsible for ADP-induced platelet aggregation. By blocking this receptor, clopidogrel prevents the activation and aggregation of platelets, reducing the risk of clot formation. This mechanism of action is important in preventing thrombotic events in patients with cardiovascular diseases.

Explanation

Clopidogrel irreversibly blocks the P2Y12 receptor, which is responsible for ADP-induced platelet aggregation. By blocking this receptor, clopidogrel prevents the activation and aggregation of platelets, reducing the risk of clot formation. This mechanism of action is important in preventing thrombotic events in patients with cardiovascular diseases.

5. A 45-year-old man is evaluated by his primary care physician for complaints of early satiety and weight loss. On physical examination, his spleen is palpable 10 cm below the left costal margin and is mildly tender to palpation. His laboratory studies show a leukocyte count of 125,000/ L with a differential of 80% neutrophils, 9% bands, 3% myelocytes, 3% metamyelocytes, 1% blasts, 1% lymphocytes, 1% eosinophils, and 1% basophils. Hemoglobin is 8.4 g/dL, hematocrit 26.8%, and platelet count 668,000/ L. A bone marrow biopsy demonstrates increased cellularity with an increased myeloid to erythroid ratio. Which of the following cytogenetic abnormalities is most likely to be found in this patient?

Deletion of a portion of the long arm of chromosome 5, del (5q)

Inversion of chromosome 16, inv(16)

Reciprocal translocation between chromosomes 9 and 22 (Philadelphia chromosome)

Translocations of the long arms of chromosomes 15 and 17

Trisomy 12

The patient in this scenario presents with splenomegaly, leukocytosis, anemia, and thrombocytosis, which are characteristic findings of chronic myeloid leukemia (CML). The presence of the Philadelphia chromosome, resulting from a reciprocal translocation between chromosomes 9 and 22, is a hallmark cytogenetic abnormality in CML. This translocation leads to the formation of the BCR-ABL fusion gene, which produces a constitutively active tyrosine kinase that drives the proliferation of myeloid cells. The other options listed are not associated with the clinical and laboratory findings described in this patient.

Explanation

The patient in this scenario presents with splenomegaly, leukocytosis, anemia, and thrombocytosis, which are characteristic findings of chronic myeloid leukemia (CML). The presence of the Philadelphia chromosome, resulting from a reciprocal translocation between chromosomes 9 and 22, is a hallmark cytogenetic abnormality in CML. This translocation leads to the formation of the BCR-ABL fusion gene, which produces a constitutively active tyrosine kinase that drives the proliferation of myeloid cells. The other options listed are not associated with the clinical and laboratory findings described in this patient.

6. Fondaparinux may be used to treat all of the following patients except

A 68-year-old man has undergone an uncomplicated right total hip replacement.

Fondaparinux is a selective factor Xa inhibitor that is commonly used for the treatment of deep venous thrombosis (DVT) and pulmonary embolism (PE). However, in patients with severe renal impairment, such as the 46-year-old man in this case with a baseline creatinine of 3.3 mg/dL, fondaparinux should be used with caution or avoided altogether due to the risk of accumulation and increased bleeding. Therefore, fondaparinux may not be suitable for this patient.

Explanation

Fondaparinux is a selective factor Xa inhibitor that is commonly used for the treatment of deep venous thrombosis (DVT) and pulmonary embolism (PE). However, in patients with severe renal impairment, such as the 46-year-old man in this case with a baseline creatinine of 3.3 mg/dL, fondaparinux should be used with caution or avoided altogether due to the risk of accumulation and increased bleeding. Therefore, fondaparinux may not be suitable for this patient.

7. A 55-year-old female presents with progressive incoordination. Physical examination is remarkable for nystagmus, mild dysarthria, and past-pointing on finger-to-nose testing. She also has an unsteady gait. MRI reveals atrophy of both lobes of the cerebellum. Serologic evaluation reveals the presence of anti-Yo antibody. Which of the following is the most likely cause of this clinical syndrome?

Non-small cell cancer of the lung

Small-cell cancer of the lung

Breast cancer

Non-Hodgkin's lymphoma

Colon Cancer

The patient's clinical presentation with progressive incoordination, nystagmus, dysarthria, past-pointing, and atrophy of both lobes of the cerebellum suggests a cerebellar syndrome. The presence of anti-Yo antibody is highly specific for paraneoplastic cerebellar degeneration (PCD), which is commonly associated with gynecological and breast cancers. Therefore, the most likely cause of this clinical syndrome is breast cancer.

Explanation

The patient's clinical presentation with progressive incoordination, nystagmus, dysarthria, past-pointing, and atrophy of both lobes of the cerebellum suggests a cerebellar syndrome. The presence of anti-Yo antibody is highly specific for paraneoplastic cerebellar degeneration (PCD), which is commonly associated with gynecological and breast cancers. Therefore, the most likely cause of this clinical syndrome is breast cancer.

8. Which of the following tumor characteristics confers a poor prognosis in patients with breast cancer?

Estrogen receptor-positive

Good nuclear grade

Low proportion of cells in S-phase

Overexpression of erbB2 (HER-2/neu)

Progesterone receptor-positive

Overexpression of erbB2 (HER-2/neu) confers a poor prognosis in patients with breast cancer because it is associated with aggressive tumor behavior and resistance to certain treatments. HER-2/neu is a protein that promotes cell growth and division, and when it is overexpressed, it can lead to uncontrolled cell proliferation and tumor progression. This type of breast cancer is often more aggressive and less responsive to hormone therapy, making it more difficult to treat and resulting in a poorer prognosis for patients.

Explanation

Overexpression of erbB2 (HER-2/neu) confers a poor prognosis in patients with breast cancer because it is associated with aggressive tumor behavior and resistance to certain treatments. HER-2/neu is a protein that promotes cell growth and division, and when it is overexpressed, it can lead to uncontrolled cell proliferation and tumor progression. This type of breast cancer is often more aggressive and less responsive to hormone therapy, making it more difficult to treat and resulting in a poorer prognosis for patients.

9. A healthy 62-year-old woman returns to your clinic after undergoing routine colonoscopy. Findings included two 1.3-cm sessile (flat-based), villous adenomas in her ascending colon that were removed during the procedure. What is the next step in management?

Colonscopy in 3 months

Colonscopy in 3 years

Colonscopy in 10 years

CT scan of the abdomen

Partial colectomy

Reassurance

The next step in management for a healthy 62-year-old woman with two 1.3-cm sessile, villous adenomas in her ascending colon that were removed during routine colonoscopy is to schedule a colonoscopy in 3 years. This is because villous adenomas have a higher risk of developing into colorectal cancer compared to other types of adenomas. Therefore, regular surveillance colonoscopy is recommended to monitor for any recurrence or development of new adenomas.

Explanation

The next step in management for a healthy 62-year-old woman with two 1.3-cm sessile, villous adenomas in her ascending colon that were removed during routine colonoscopy is to schedule a colonoscopy in 3 years. This is because villous adenomas have a higher risk of developing into colorectal cancer compared to other types of adenomas. Therefore, regular surveillance colonoscopy is recommended to monitor for any recurrence or development of new adenomas.

10. A 34-year-old woman presents for evaluation of left lower extremity swelling and pain. She is obese and 8 weeks postpartum. She recently traveled 6 h by airplane to visit her parents with her infant. She has had no dyspnea, palpitations, or syncope. She is currently on no medications except iron tablets. She is otherwise healthy. Her vitals signs are: heart rate 86 beats/min, blood pressure 110/80 mm/Hg, temperature 37.0°C, and respiratory rate 12 breaths/min. Her weight is 98 kg, and height is 170 cm. The left lower extremity is swollen, tender, and warm to touch. A Homan's sign is present, but there are no palpable cords. A lower extremity Doppler shows a thrombosis in the common and superficial femoral veins of the left leg. You are considering outpatient treatment with enoxaparin. All of the following statements regarding low-molecular-weight heparins (LMWH) are true except:

LMWH can be safely used in pregnancy, but factor Xa levels should be monitored to ensure adequate anticoagulation

Monitoring of factor Xa levels is unnecessary in most patients as there is a predictable dose-dependent anticoagulation effect.

There is a decrease in the risk of development of heparin-induced thrombocytopenia with use of LMWH.

LMWH can be safely used in pregnancy, but factor Xa levels should be monitored to ensure adequate anticoagulation. Monitoring of factor Xa levels is unnecessary in most patients as there is a predictable dose-dependent anticoagulation effect. There is a decrease in the risk of development of heparin-induced thrombocytopenia with the use of LMWH. However, this patient's recent pregnancy is a contraindication to the use of LMWH because there is a greater risk of bleeding with LMWH compared to IV heparin.

Explanation

LMWH can be safely used in pregnancy, but factor Xa levels should be monitored to ensure adequate anticoagulation. Monitoring of factor Xa levels is unnecessary in most patients as there is a predictable dose-dependent anticoagulation effect. There is a decrease in the risk of development of heparin-induced thrombocytopenia with the use of LMWH. However, this patient's recent pregnancy is a contraindication to the use of LMWH because there is a greater risk of bleeding with LMWH compared to IV heparin.

11. All of the enzyme deficiencies that lead to porphyrias are inherited either as autosomal dominant (AD) or autosomal recessive (AR) traits with one exception. Which of the following most commonly occurs sporadically?

5-ALA dehydratase-deficient porphyria

Acute intermittent porphyria

Erythropoietic porphyria

Porphyria cutanea tarda

Variegate porphyria

Porphyria cutanea tarda most commonly occurs sporadically. This means that it is not typically inherited from a parent but instead arises spontaneously. While most enzyme deficiencies that lead to porphyrias are inherited as autosomal dominant or autosomal recessive traits, porphyria cutanea tarda is an exception and often occurs without a family history of the condition.

Explanation

Porphyria cutanea tarda most commonly occurs sporadically. This means that it is not typically inherited from a parent but instead arises spontaneously. While most enzyme deficiencies that lead to porphyrias are inherited as autosomal dominant or autosomal recessive traits, porphyria cutanea tarda is an exception and often occurs without a family history of the condition.

12. A new screening test for thyroid cancer has been introduced into the population. In the first year, 1000 positive tests lead to correct identification of thyroid cancer in the screened population. Over the next year, 250 cases of thyroid cancer are detected among those who initially had a negative test. What is the sensitivity of this new screening test?

25%

67%

80%

Not enough information to calculate

The sensitivity of a screening test refers to its ability to correctly identify individuals who have the condition being tested for. In this case, the test correctly identified 1000 cases of thyroid cancer out of the total screened population. The sensitivity can be calculated by dividing the number of true positives (1000) by the sum of true positives (1000) and false negatives (250). Therefore, the sensitivity of this new screening test is 80%.

Explanation

The sensitivity of a screening test refers to its ability to correctly identify individuals who have the condition being tested for. In this case, the test correctly identified 1000 cases of thyroid cancer out of the total screened population. The sensitivity can be calculated by dividing the number of true positives (1000) by the sum of true positives (1000) and false negatives (250). Therefore, the sensitivity of this new screening test is 80%.

13. Which of the following serum laboratory tests is most useful for predicting return of renal function in a patient with tumor lysis syndrome and acute renal failure?

Creatinine

Phosphate

Potassium

Serum pH

Uric acid

Uric acid is the most useful serum laboratory test for predicting the return of renal function in a patient with tumor lysis syndrome and acute renal failure. Tumor lysis syndrome can lead to the release of large amounts of uric acid into the bloodstream, which can cause kidney damage. Monitoring uric acid levels can help determine the severity of renal dysfunction and guide treatment decisions. As renal function improves, uric acid levels tend to decrease, indicating recovery of kidney function. Therefore, uric acid is a valuable marker in predicting the return of renal function in this scenario.

Explanation

Uric acid is the most useful serum laboratory test for predicting the return of renal function in a patient with tumor lysis syndrome and acute renal failure. Tumor lysis syndrome can lead to the release of large amounts of uric acid into the bloodstream, which can cause kidney damage. Monitoring uric acid levels can help determine the severity of renal dysfunction and guide treatment decisions. As renal function improves, uric acid levels tend to decrease, indicating recovery of kidney function. Therefore, uric acid is a valuable marker in predicting the return of renal function in this scenario.

14. A woman with advanced breast cancer being treated with tamoxifen presents to the emergency department with nausea and vomiting. She has been tolerating her treatment well but in the last 3 days noticed nausea, vomiting, and abdominal pain. Her symptoms are not related to food intake, and she is having normal bowel movements. She has no fevers or rashes. Her medications include tamoxifen, alendronate, megestrol acetate, and a multivitamin. Abdominal examination reveals very mild tenderness diffusely, and there is no rebound tenderness. Bowel sounds are normal. Plain radiographs and a CT scan of the abdomen are unremarkable. Laboratory analysis reveals a normal white blood cell count. Sodium is 130 meq/L, potassium 4.9 meq/L, chloride 99 meq/L, bicarbonate 29 meq/L, BUN 15 mg/dL, creatinine 0.7 mg/dL. What is the next most appropriate step in this patient's management?

Antemetics prn

Laparoscopy

Serum cortisol

Small-bowel follow through

Upper endoscopy

The patient's symptoms of nausea, vomiting, and abdominal pain, along with the normal bowel movements and unremarkable imaging studies, suggest that her symptoms may be due to adrenal insufficiency. This can be caused by long-term use of megestrol acetate, which is a synthetic progestin. Checking serum cortisol levels is the most appropriate next step to evaluate for adrenal insufficiency.

Explanation

The patient's symptoms of nausea, vomiting, and abdominal pain, along with the normal bowel movements and unremarkable imaging studies, suggest that her symptoms may be due to adrenal insufficiency. This can be caused by long-term use of megestrol acetate, which is a synthetic progestin. Checking serum cortisol levels is the most appropriate next step to evaluate for adrenal insufficiency.

15. You are asked to consult on a 31-year-old male with prolonged bleeding after an oral surgery procedure. He has no prior history of bleeding diathesis or family history of bleeding disorders. The patient's past medical history is remarkable for infection with the human immunodeficiency virus, with a CD4 count of 51/mL3. The examination is remarkable only for spotty lymphadenopathy. The platelet count is 230,000 cells/mL. His international normalized ratio (INR) is 1.5. Activated partial thromboplastin time is 40 s. Peripheral blood smear shows no schistocytes and is otherwise unremarkable. A 1:1 mixing study corrects both conditions immediately and after a 2-h incubation. Fibrinogen level is normal. Thrombin time is prolonged. What is the diagnosis?

Disseminated intravascular coagulation (DIC)

Dysfibrinogenemia

Factor V deficiency

Liver disease

Factor XIII deficiency

The patient's prolonged bleeding after oral surgery, along with a normal platelet count and normal fibrinogen level, suggests a disorder involving the clotting factors. The prolonged thrombin time and correction of both conditions in the mixing study indicate a dysfunction in fibrinogen. Dysfibrinogenemia is a rare inherited disorder characterized by abnormal fibrinogen molecules, leading to impaired clot formation and increased bleeding tendency. This diagnosis is supported by the absence of schistocytes on the peripheral blood smear and the patient's medical history, which does not suggest liver disease or factor deficiencies.

Explanation

The patient's prolonged bleeding after oral surgery, along with a normal platelet count and normal fibrinogen level, suggests a disorder involving the clotting factors. The prolonged thrombin time and correction of both conditions in the mixing study indicate a dysfunction in fibrinogen. Dysfibrinogenemia is a rare inherited disorder characterized by abnormal fibrinogen molecules, leading to impaired clot formation and increased bleeding tendency. This diagnosis is supported by the absence of schistocytes on the peripheral blood smear and the patient's medical history, which does not suggest liver disease or factor deficiencies.

16. A 65-year-old man seeks evaluation for nasal congestion, headaches, and dysphagia, most notably when he lies supine for sleeping. These symptoms have been slowly worsening for the past month. He has no nasal discharge or fevers. On review of systems, he reports recent hoarseness and dizziness. His past medical history is significant only for mild hypertension. He worked as a roofing contractor and smoked one pack/day of cigarettes since age 16. On physical examination, you note facial edema. His oropharynx is also mildly edematous, and the tonsils are unremarkable. His external and internal jugular veins are engorged bilaterally, and there are prominent veins on the anterior chest. Chest percussion reveals dullness in the right base with decreased tactile fremitus. A chest radiograph shows a right upper lung mass that on biopsy is consistent with non-small cell lung cancer. All of the following treatments may help this patient's symptoms except

Chemotherapy

Diuretics

Glucocorticoids

Radiation therapy

Venous stenting

Glucocorticoids are not effective in treating the symptoms described in the patient, which include nasal congestion, headaches, dysphagia, hoarseness, and dizziness. Glucocorticoids are commonly used to reduce inflammation and suppress the immune system, but they would not directly address the underlying causes of the patient's symptoms, such as the lung mass causing compression of nearby structures. Chemotherapy, diuretics, radiation therapy, and venous stenting may all be potential treatments for this patient's symptoms, as they can target the underlying cause or provide symptom relief.

Explanation

Glucocorticoids are not effective in treating the symptoms described in the patient, which include nasal congestion, headaches, dysphagia, hoarseness, and dizziness. Glucocorticoids are commonly used to reduce inflammation and suppress the immune system, but they would not directly address the underlying causes of the patient's symptoms, such as the lung mass causing compression of nearby structures. Chemotherapy, diuretics, radiation therapy, and venous stenting may all be potential treatments for this patient's symptoms, as they can target the underlying cause or provide symptom relief.

17. A 73-year-old male presents to the clinic with 3 months of increasing back pain. He localizes the pain to the lumbar spine and states that the pain is worst at night while he is lying in bed. It is improved during the day with mobilization. Past history is notable only for hypertension and remote cigarette smoking. Physical examination is normal. Laboratory studies are notable for an elevated alkaline phosphatase. A lumbar radiogram shows a lytic lesion in the L3 vertebra. Which of the following malignancies is most likely?

Gastric carcinoma

Non-small cell lung cancer

Osteosarcoma

Pancreatic carcinoma

Thyroid carcinoma

The patient's presentation of increasing back pain localized to the lumbar spine, worsened at night, and improved with mobilization, along with an elevated alkaline phosphatase and a lytic lesion in the L3 vertebra on lumbar radiogram, is suggestive of metastatic bone disease. Osteosarcoma is a malignant bone tumor that commonly metastasizes to the lumbar spine and can present with similar symptoms and radiographic findings. The patient's age and past medical history are not specific for any particular malignancy.

Explanation

The patient's presentation of increasing back pain localized to the lumbar spine, worsened at night, and improved with mobilization, along with an elevated alkaline phosphatase and a lytic lesion in the L3 vertebra on lumbar radiogram, is suggestive of metastatic bone disease. Osteosarcoma is a malignant bone tumor that commonly metastasizes to the lumbar spine and can present with similar symptoms and radiographic findings. The patient's age and past medical history are not specific for any particular malignancy.

18. A 36-year-old African-American woman with systemic lupus erythematosus presents with the acute onset of lethargy and jaundice. On initial evaluation, she is tachycardic, hypotensive, appears pale, is dyspneic, and is somewhat difficult to arouse. Physical examination reveals splenomegaly. Her initial hemoglobin is 6 g/dL, white blood cell count is 6300/ L, and platelets are 294,000/ L. Her total bilirubin is 4 g/dL, reticulocyte count is 18%, and haptoglobin is not detectable. Renal function is normal, as is urinalysis. What would you expect on her peripheral blood smear?

Macrocytosis and PMN's with hypersegmented nuclei

Microspherocytes

Schistocytes

Sickle cells

Target cells

The presence of microspherocytes on the peripheral blood smear suggests a diagnosis of autoimmune hemolytic anemia, which can occur in patients with systemic lupus erythematosus. Microspherocytes are small, round red blood cells that lack central pallor and have a dense appearance. They are a result of the immune system targeting and destroying red blood cells. The other options listed are not consistent with the clinical presentation and laboratory findings described in the question.

Explanation

The presence of microspherocytes on the peripheral blood smear suggests a diagnosis of autoimmune hemolytic anemia, which can occur in patients with systemic lupus erythematosus. Microspherocytes are small, round red blood cells that lack central pallor and have a dense appearance. They are a result of the immune system targeting and destroying red blood cells. The other options listed are not consistent with the clinical presentation and laboratory findings described in the question.

19. A 52-year-old man is admitted with recurrent hemarthroses of his knees. He is an electrician who is still working but over the last year has had recurrent hemarthroses requiring surgical evacuation. Before one year ago, he had no medical problems. He has no other past medical history and seldom sees a physician. He smokes tobacco regularly. His platelet count is normal, erythrocyte sedimentation rate is 55 mm/hr, hemoglobin is 9 mg/dL and albumin is 3.1 mg/dL. Coagulation studies show a prolonged activated partial thromboplastin time (aPTT) and a normal prothrombin time (PT). Adding plasma from a normal subject does not correct the aPTT. What is the cause of his recurrent hemarthroses?

Acquired inhibitor

Factor VIII deficiency

Factor IX deficiency

Secondary syphilis

Vitamin C deficiency

The patient's prolonged activated partial thromboplastin time (aPTT) and normal prothrombin time (PT) suggest a clotting factor deficiency. The fact that adding plasma from a normal subject does not correct the aPTT indicates the presence of an acquired inhibitor, which is causing the deficiency. This is supported by the patient's normal platelet count and the absence of other medical problems that could cause clotting factor deficiencies. Therefore, the most likely cause of his recurrent hemarthroses is an acquired inhibitor.

Explanation

The patient's prolonged activated partial thromboplastin time (aPTT) and normal prothrombin time (PT) suggest a clotting factor deficiency. The fact that adding plasma from a normal subject does not correct the aPTT indicates the presence of an acquired inhibitor, which is causing the deficiency. This is supported by the patient's normal platelet count and the absence of other medical problems that could cause clotting factor deficiencies. Therefore, the most likely cause of his recurrent hemarthroses is an acquired inhibitor.