This week, we are sharing another USMLE® Step 1-style practice question to test your knowledge of medical topics. Today’s case focuses on a 56-year-old man who has recently immigrated from Vietnam. He experiences worsening fatigue and decreasing exercise tolerance. Can you figure it out?
A 56-year-old man presents to his primary care physician with worsening fatigue, decreasing exercise tolerance and a 15 pound weight loss over the past two months. The patient additionally has a chronic cough, low grade fevers, and cravings for salty foods. He currently lives in Ohio but recently immigrated from Vietnam, where he worked as a nurse. He has a history of type II diabetes mellitus and a ten pack year smoking history, but he does not use alcohol or other illicit substances. Temperature is 37.0°C (98.6 °F), pulse is 65/min, respirations are 16/min, blood pressure is 100/72 mmHg, and oxygen saturation is 95% on room air. Physical examination demonstrates a thin, fatigued male in no acute distress with facial hyperpigmentation. A screening PPD test is positive. Which of the following is the most likely etiology of this patient’s clinical presentation?
A. Chronic mycobacterial infection
B. Infection with a gram-negative diplococci
C. Disseminated histoplasmosis
D. Presence of HLA-B8
E. Metastatic lung malignancy
Scroll down to find the answer!
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The correct answer to today’s USMLE® Step 1 Question is…
A. Chronic mycobacterial infection
Before we get to the Main Explanation, let’s look at the incorrect answer explanations. Skip to the bottom if you want to see the correct answer right away!
Incorrect answer explanations
The incorrect answers to today’s USMLE® Step 1 Question are…
B. Infection with a gram-negative diplococci
Incorrect: Infection with Neisseria meningitidis can result in Waterhouse-Friderichsen syndrome and bilateral adrenal hemorrhage. Clinically, this complication presents with acute disseminated intravascular coagulation and refractory shock, which are absent in this patient.
C. Disseminated histoplasmosis
Incorrect: Disseminated histoplasmosis can cause primary adrenal insufficiency. However, it is not the most common etiology of adrenal insufficiency in patients from developing countries. Furthermore, disseminated histoplasmosis rarely manifests in immunocompetent patients.
D. Presence of HLA-B8
Incorrect: Autoimmune adrenalitis is associated with the HLA-B8 serotype. Given the patient’s risk factors and clinical features consistent with Mycobacterium tuberculosis infection, this diagnosis is less likely.
E. Metastatic lung malignancy
Incorrect: Metastatic malignancies can cause primary adrenal insufficiency when tumor burden spreads to the adrenal glands. Although this patient does smoke, his positive PPD test makes mycobacterial infection a more likely cause of his adrenal insufficiency.
Main Explanation
This patient presents with worsening fatigue, low grade fevers, weight loss, and skin hyperpigmentation. In addition, he has a history of working as a nurse in a country endemic to Mycobacterium tuberculosis, which is the most common etiology of primary adrenal insufficiency in the developing world. His screening PPD test is positive, which further supports this diagnosis.
Primary adrenal insufficiency refers to decreased production of both mineralocorticoids and glucocorticoids due to adrenal gland dysfunction. This disease is further divided into acute and chronic forms, with acute disease characterized by refractory shock due to adrenal hemorrhage from acute infectious etiologies, thrombosis, or trauma.
Chronic adrenal insufficiency is characterized by indolent symptoms that commonly include fatigue, weight loss, salt craving, and non-specific gastrointestinal complaints. Patients will frequently have signs of hypotension, skin hyperpigmentation, and electrolyte abnormalities of hyponatremia, hyperkalemia, and metabolic acidosis. Etiologies of chronic adrenal insufficiency are divided into autoimmune causes, infectious etiologies, drugs, and metastatic disease. In the developed world, autoimmune adrenalitis is the most common cause of primary adrenal insufficiency, whereas in the developing world the most common etiology is chronic Mycobacterium tuberculosis infection.infection.
Major Takeaway
Primary adrenal insufficiency is divided into acute and chronic forms. In the developing world, the most common etiology of primary adrenal insufficiency is Mycobacterium tuberculosis infection.
References
Bancos, I., Hahner, S., Tomlinson, J., Arlt, W. (2015) Diagnosis and management of adrenal insufficiency. The Lancet Diabetes & Endocrinology. 3(3), 216‐226. Doi: 10.1016/S2213-8587(14)70142-1.
Charmandari, E., Nicolaides, N.C., Chrousos, G.P. (2014) Adrenal insufficiency. Lancet. 383(9935), 2152‐2167. Doi: 10.1016/S0140-6736(13)61684-0.
Herndon, J., Nadeau, A.M., Davidge-Pitts, C.J., Young, W.F., Bancos, I. (2018) Primary adrenal insufficiency due to bilateral infiltrative disease. Endocrine. 62(3), 721‐728. Doi: 10.1007/s12020-018-1737-7.
Jameson, J. L. (2018) Harrison’s principles of internal medicine. New York: McGraw-Hill Education. ISBN: 9781259644030.
Kumar, V., Abbas, A.K., Aster, J.C., Perkins, J.A., Robbins, S.L. (2018) Robbins basic pathology (10th ed.). Philadelphia, PA: Elsevier. ISBN: 978-0-323-35317-5.
Pulzer, A., Burger-Stritt, S., Hahner, S. (2016). Morbus Addison: Primäre Nebenniereninsuffizienz [Addison’s disease : Primary adrenal insufficiency]. Der Internist. 57(5), 457‐469. Doi: 10.1007/s00108-016-0054-6.
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