Diabetes mellitus: Clinical

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Diabetes mellitus: Clinical

USMLE® Step 2 questions

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A 55-year-old man comes to the emergency department with fevers and a cough for the past week. The fever is intermittent and associated with a dull headache. The cough is non-productive, and the patient denies sore throat, nasal congestion, shortness of breath, or chest pain. He has a history of type 2 diabetes mellitus diagnosed 5 years ago. Initially, the patient was prescribed oral antihyperglycemics, but he switched to herbal remedies after one month because of side effects. The patient has never smoked cigarettes. He is employed as a groundskeeper at a local country club. The patient’s temperature is 36.4°C (97.5°F), pulse is 100/min, respirations are 20/min, and blood pressure is 120/70 mmHg. Physical examination shows occasional coarse left-sided crackles on lung auscultation. Neurologic and skin examinations are normal. Serum laboratory studies show the following:  
 Laboratory value  Result 
 White blood cells  28,000 /mm3 
 Creatinine  2.3 mg/dL 
 Glucose  374 mg/dL 
 Bicarbonate  19 mEq/L 
 Ketones  Positive 
Chest X-ray shows homogenous opacities in the left upper lobe. Nasal endoscopy shows extensive inflammation of the left nasal cavity and maxillary sinus. Sputum microscopy shows the following:  

 Reproduced from: Wikimedia Commons  

Which of the following antimicrobial agents is most appropriate to administer to this patient?


In diabetes mellitus, the body has trouble moving glucose from your blood into the cells – so blood sugar levels are constantly high. Insulin stimulates the movement of glucose into the cells, and glucagon stimulates the movement of glucose into the blood. In type I diabetes the blood glucose stays high because of an autoimmune destruction of the pancreas, which leads to low insulin levels. In type II diabetes, the body makes insulin, but the cells are insulin resistant - meaning they don’t “respond” to insulin by taking glucose in.

Cells’ inability to use insulin translates in classical symptoms of diabetes like polyuria – individuals pee a lot -, polydipsia – they drink a lot of water -, sometimes polyphagia – they eat a lot – and unexplained weight loss. Both type I and type II diabetes get these symptoms – however, with type I, the onset is usually abrupt and usually affects people under 30. With type II, the symptoms gradually worsen over a few months, and individuals usually have risk factors like being over 45 years old, having a first degree relative with type II diabetes mellitus, a body mass index (BMI) over 25, a sedentary lifestyle, or cardiovascular disease, like hypertension.

Now, type II diabetes accounts for about 90% of the diabetes cases, so let’s start there. Diagnosing type II diabetes relies on determining blood sugar levels using one of four tests. The first, and most common test, is a fasting glucose test and it’s where the person doesn’t eat or drink anything except water for 8 hours. Levels of 100 milligrams per deciliter to 125 milligrams per deciliter indicates prediabetes and a level of 126 milligrams per deciliter or higher indicates diabetes. Usually this test is done twice, and two results over 126 milligrams per deciliter are sufficient to diagnose a person with diabetes. Second, we have the oral glucose tolerance test, and it’s where a person is given 75 grams of glucose, and then blood samples are taken at time intervals to figure out how well it’s being cleared from the blood. At the time interval of 2 hours later, a level of 140 milligrams per deciliter to 199 milligrams per deciliter indicates prediabetes, and a level of 200 or above indicates diabetes. However, these two tests have one shortcoming - they only show what’s happening to blood glucose levels in that particular moment in time, so we have no idea how long blood sugar levels have been high. This is where our third test comes in - the HbA1c, which is the proportion of glycated hemoglobin in the blood. When blood glucose levels stay high for too long, glucose begins to stick to proteins that are floating around in the blood or in cells - like hemoglobin. HbA1c levels of 5.7% to 6.4% indicate prediabetes, and 6.5% or higher indicates diabetes. Since red blood cells - and hemoglobin - typically hang around in the blood for up to 4 months, this test reflects blood glucose levels over the past few months. Finally, there’s our fourth test, called a non-fasting or random glucose test, which can be done at any time. A red flag for diabetes is when this test shows a blood glucose level of 200 milligrams per deciliter or higher in an individual that has classic symptoms, like polyuria or polydipsia; or a hyperglycemic crisis.


Diabetes mellitus is a metabolic condition characterized by high blood sugar levels (glycemia). The two types of diabetes mellitus are type 1 and type 2. Type 1 Diabetes Mellitus, also called insulin-dependent diabetes, usually begins in childhood or adolescence. In this form of the disease, an autoimmune process triggers the destruction of pancreatic beta cells responsible for producing insulin, and thus the body produces little or no insulin. Insulin is a hormone that helps the body to use sugar for energy.

Type 2 diabetes mellitus, also called non-insulin-dependent diabetes, usually begins in adulthood. In this type, the body produces insulin but becomes resistant to it, meaning it cannot use it effectively. Type 2 diabetes mellitus has a genetic component, and a sedentary lifestyle and obesity significantly elevate its risk.


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