A 37-year-old man with a history of Crohn disease presents with several months of worsening fatigue. The patient reports 1 to 2 glasses of wine per night with dinner, but denies smoking or illicit drug use. Physical examination shows conjunctival pallor. Laboratory results reveal the following:
The patient is started on folic acid and 4 weeks later presents with a hemoglobin level of 10.1 mg/dL. However, he reports a new “pins and needles” sensation in his distal toes and fingers.
Which of the following is the underlying cause of the patient’s CURRENT symptoms?
Vitamin B12 deficiency. The patient in this question likely has cobalamin (vitamin B12) deficiency. This results in megaloblastic anemia. Long-term consequences of vitamin B12 deficiency include peripheral neuropathy and posterior column defects from abnormal myelin synthesis. Importantly, folic acid deficiency is another cause of macrocytic anemia and treatment with folic acid can improve the actual anemia of vitamin B12 deficiency since both folate and vitamin B12 are involved in the conversion of homocysteine to methionine. However, neurologic symptoms can be worsened in vitamin B12 deficiency with the treatment of folic acid since vitamin B12 is used in other biologic processes as well. As a result, it is critical to rule out vitamin B12 deficiency prior to initiating folic acid. Vitamin B12 deficiency results from inadequate vitamin B12 intake (diet lacking in animal products) and autoimmune gastritis. The loss of gastric parietal cells secondary to autoimmune gastritis causes intrinsic factor deficiency (which is necessary for vitamin B12 absorption in the terminal ileum).
(A) The patient’s underlying disorder is vitamin B12 deficiency and no amount of folic acid supplementation will improve his neurologic symptoms. (B) Iron deficiency is microcytic anemia (MCV <80 fL) and is not associated with peripheral neuropathy. (C) Although glucose intolerance commonly causes peripheral neuropathy, this patient does not have a history that suggests diabetes.
A 48-year-old woman with no past medical history presents with weakness and double vision for the past 7 months. The patient reports that the weakness is worse at the end of the day. Her family history is significant for hypertension and diabetes. Physical examination shows mild bilateral ptosis. Laboratory studies (thyroid studies, complete blood count, and comprehensive metabolic panel) are ordered and are all within normal limits. The patient’s acetylcholine receptor antibody test is positive.
What is the best next step in the management of this patient?
CT scan of the chest. The patient in this question is presenting with signs and symptoms of myasthenia gravis (MG), which is confirmed with the acetylcholine receptor antibody test. This disorder manifests with weakness of the muscles (particularly at the end of the day), ptosis, and/ or double vision. Shortness of breath is of serious concern in MG since respiratory muscle fatigue can lead to respiratory failure and death. After establishing the diagnosis, it is crucial to rule out a thymoma with a CT scan of the chest. Treatment of MG consists of acetylcholinesterase inhibitors and immunosuppressive drugs.
(A) The diagnosis is already established with the positive result of the acetylcholine receptor antibody test, so there is no need to perform an edrophonium test (which is less sensitive anyways). (C) Muscle biopsy can be considered if the diagnosis of MG is difficult or when myositis is suspected as the cause of the symptoms. (D) Immunosuppressive drugs are part of the treatment of MG, but the next step is to screen for thymoma in newly diagnosed MG patients.
A 37-year-old woman with an insignificant past medical history presents with fatigue and occasional shortness of breath for the last 9 months. The patient reports that she does not drink alcohol or smoke. Physical examination reveals a blood pressure of 100/60 mmHg, heart rate of 104 beats per minute, and conjunctival pallor. Laboratory values reveal the following:
Which of the following is the best next step in management of this patient?
Serum iron studies. The patient in this question is presenting with microcytic anemia (MCV <80 fL). The differential diagnosis of microcytic anemia can be remembered by the mnemonic “TAILS” (Thalassemia, Anemia of chronic disease, Iron deficiency anemia, Lead poisoning, Sideroblastic anemia). The most common cause of microcytic anemia is iron deficiency and the best next step is ordering iron studies: serum iron, total iron-binding capacity (TIBC), and serum ferritin. In iron deficiency anemia, serum iron is typically low, TIBC is increased, and serum ferritin is low. After iron-deficiency anemia is confirmed, the underlying cause should be determined. Iron deficiency is by far the most common cause of microcytic anemia, so a trial of iron supplementation is often performed instead of an extensive workup.
(B) Hemoglobin electrophoresis would be useful for diagnosing thalassemia. β-thalassemia trait usually has reduced or absent HbA, elevated levels of HbA2, and increased HbF. (C) Although lead poisoning is a cause of microcytic anemia, it is uncommon and should only be sought after iron deficiency anemia has been ruled out. (D) Peripheral blood smear is often used to exclude sideroblastic anemia, but this is an uncommon cause of microcytic anemia.
A 27-year-old woman presents with shortness of breath and worsening fatigue for the last month. She has a history of type 2 diabetes mellitus and mild intermittent asthma. Her family history is significant for breast cancer and hypertension. On physical examination, her blood pressure is 108/72 mmHg, heart rate is 102 beats per minute, and respiratory rate is 14 breaths per minute. There is conjunctival pallor and scleral icterus. Laboratory results reveal the following:
Peripheral blood smear is performed and shows spherocytes without central pallor.
Which of the following is the most likely diagnosis in this patient?
Autoimmune hemolytic anemia (AIHA). The patient in this question is presenting with symptoms and signs consistent with a hemolytic anemia. Hemolytic anemias cause elevated total and indirect bilirubin, elevated LDH, and decreased haptoglobin. Pallor, icterus, and splenomegaly might be present on physical examination. The two broad categories of hemolytic anemia include intravascular hemolysis and extravascular hemolysis. In intravascular hemolysis, the RBCs are lysed within the blood vessel (i.e., mechanical valve damage or complement fixation). In extravascular hemolysis, RBCs are phagocytized by macrophages in the spleen, liver, and bone marrow. This patient’s peripheral blood smear shows spherocytes without central pallor, which can be seen in both AIHA and hereditary spherocytosis. (B) However, AIHA has a positive Coombs test whereas hereditary spherocytosis has a negative Coombs test, positive osmotic fragility test, and a strong family history (it is autosomal dominant). (A) Iron-deficiency anemia causes microcytic anemia and this patient has normocytic anemia. (D) Vitamin B12 deficiency causes macrocytic anemia.
A 47-year-old woman who is undergoing chemotherapy for metastatic melanoma presents to the Emergency Department with fevers, chills, and weakness for the past 18 hours. The patient endorses no other complaints. She has a temperature of 39°C, blood pressure of 120/80 mmHg, heart rate of 106 beats per minute, and respiratory rate of 16 breaths per minute. Physical examination is unremarkable. Laboratory results reveal the following:
A urinalysis is unremarkable and a chest x-ray shows no infiltrates.
Which of the following is the most appropriate next step in management of this patient?
Draw blood cultures and initiate IV piperacillin– tazobactam. The patient in this question has febrile neutropenia, defined as an isolated temperature of greater than 38.3°C or sustained temperature of greater than 38.0°C for at least an hour in a neutropenic patient. Neutropenia is defined as an absolute neutrophil count (ANC) less than 1,500/mm3 ; it can be further characterized as mild (ANC 1,000 to 1,500/mm3 ), moderate (ANC 500 to 1000/mm3 ), or severe (ANC <500/mm3 ). All three classifications of febrile neutropenia require antibiotics, but only moderate and severe neutropenia require admission to the hospital for IV antibiotics. This patient has moderate febrile neutropenia and is at risk for bacterial infection from a diminished neutrophil-mediated response. Patients undergoing chemotherapy are at risk for febrile neutropenia since it alters the skin and mucosal surfaces, which can cause bacterial infection via seeding into the bloodstream. The most common site in chemotherapy-induced febrile neutropenia is the gastrointestinal tract with gram-negative organisms (especially Pseudomonas aeruginosa). To avoid severe sepsis, empiric antibiotic therapy must be initiated immediately.
(A, B) Blood cultures and IV antibiotics against gram-positive and gram-negative organisms is the next step in management. Antibiotics with good Pseudomonas coverage include piperacillin–tazobactam, meropenem, and cefepime. Of note, if MRSA is a concern (particularly in the setting of catheter-related infection, skin infection, or pneumonia), vancomycin should be added. (D) This would be the answer if the patient were mildly neutropenic, hemodynamically stable, and able to tolerate oral intake.
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