USMLE Review Part I

A circular lesion in the pancreas, often seen in pancreatitis, that may indicate the presence of a pseudoabscess. This finding suggests the need for ERCP (Endoscopic Retrograde Cholangiopancreatography) to drain the abscess internally.

Emphysema is characterized by the abnormal enlargement of air spaces distal to the terminal bronchioles, often caused by destruction of alveolar walls. On a chest X-ray, this is seen as bullous changes or expanded lungs with hyperlucency.

Centri-acinar emphysema, the most common type of emphysema, is primarily located in the respiratory bronchioles and is strongly associated with cigarette smoking.

Pan-acinar emphysema, a less common type, involves the entire acinus (all parts of the respiratory bronchiole) and is typically caused by alpha-1 anti-trypsin deficiency.

A restrictive lung disease is characterized by a decrease in lung volume, leading to difficulties in expanding the lungs. This results in a normal or even increased FEV1/FVC ratio, because the lung's ability to exhale is not significantly impaired.

A bacterial infection causing watery diarrhea, typically acquired while traveling. The most common cause is enterotoxigenic Escherichia coli (ETEC) producing heat-labile (HL) or heat-stable (HS) toxins.

Caused by Clostridioides difficile, this infection manifests as bloody diarrhea, often following antibiotic use. It is diagnosed through stool toxin testing, not culture.

A serious complication of C. difficile colitis characterized by fever, abdominal distension, and potential bowel perforation. Requires emergency surgery.

A protozoan parasite causing bloody diarrhea, often acquired through contaminated food or water, especially in travel settings.

A condition characterized by a build-up of fluid in the space between the heart and the sac that surrounds it. Symptoms include muffled heart sounds, low blood pressure, and distended neck veins (JVD).

A common cause of community-acquired pneumonia (CAP), characterized by bilateral infiltrates on chest x-ray. Often presents with milder symptoms compared to other pneumonia types.

A severe form of pneumonia caused by Streptococcus pneumoniae, usually affecting a specific lobe of the lung (e.g., right lower lobe). Presents with consolidation on chest x-ray, dullness to percussion.

A life-threatening blood clot in the lungs, often arising from a deep vein thrombosis (DVT) in the legs. Presents with shortness of breath, chest pain, and leg swelling.

A common cause of fluid buildup in the middle ear, often leading to pain and discomfort in children.

The treatment for otitis media is typically oral amoxicillin for a short duration.

A condition characterized by inflammation of the outer ear canal, often caused by water exposure or irritation.

Topical ciprofloxacin and hydrocortisone drops are commonly used to treat otitis externa, addressing both infection and inflammation.

Iron deficiency anemia, thalassemia, and anemia of chronic disease are all types of microcytic anemia.

Anemia of chronic disease is characterized by low hematocrit, low MCV, and low iron, but normal or high ferritin levels. It's often associated with conditions like chronic kidney disease, rheumatoid arthritis, and lupus.

Erythropoietin (EPO) is a hormone that stimulates the production of red blood cells. In cases of anemia of chronic disease caused by renal failure, EPO treatment can be effective.

Thalassemia is a genetic disorder that affects the production of hemoglobin, leading to microcytic anemia. It's often diagnosed through hemoglobin electrophoresis.

A condition where antibodies attack the body's own hematologic cells, often with a focus on thrombocytopenia (low platelet count). Seen in autoimmune diseases like SLE.

Steroids are the primary treatment for exacerbations (flares) of SLE.

This type of lupus nephritis is characterized by the presence of "wire looping" capillaries on histology.

Mycophenolate mofetil is the primary drug used to treat lupus nephritis.

Hydroxychloroquine is a primary treatment for discoid lupus.

This specific antibody, unlike others, is highly associated with SLE.

Anti-dsDNA levels rise during SLE flare-ups, while C3 levels decrease.

Anti-histone antibodies are often found in patients with drug-induced lupus (DIL).

A condition that causes joint pain and swelling, similar to gout but caused by calcium pyrophosphate crystals instead of uric acid. It is treated similarly to gout, with medications to reduce inflammation and pain. Chronic cases may require treatment of the underlying condition.

Obesity is a significant risk factor for osteoarthritis, increasing the load on joints and contributing to cartilage breakdown.

NSAID medication decreases blood flow to the kidneys, which perceive a lower volume status. To compensate, the kidneys reabsorb more sodium, leading to water retention and peripheral edema.

Treatment for rheumatoid arthritis involves both symptom relief and disease-modifying therapy. NSAIDs are used initially for pain relief, followed by steroids if needed. However, neither slows disease progression. Methotrexate, followed by other DMARDs, is the key for slowing down RA.

Methotrexate is a dihydrofolate reductase inhibitor, interrupting the production of tetrahydrofolic acid, crucial for DNA synthesis. This impacts rapidly dividing cells, including those contributing to the inflammation of rheumatoid arthritis.

Anti-CCP (cyclic citrullinated peptide) antibodies are more specific to rheumatoid arthritis than rheumatoid factor (RF). While RF is present in a significant number of patients with RA, anti-CCP antibodies are more strongly linked to the diagnosis.

Septic arthritis is a serious infection of the joint, and any red, warm, and tender joint should be aspirated to rule it out.

Juvenile rheumatoid arthritis (JRA) is a chronic inflammatory condition affecting joints in children. Recurrent joint pain, inflammation, high ESR (erythrocyte sedimentation rate), and sometimes a rash could be indicative of this condition.

von Willebrand factor (vWF) binds to platelet GpIb and collagen, facilitating platelet adhesion to the injured vessel wall. This is distinct from platelet aggregation, which involves the binding of platelets to each other.

vWF also has a secondary function in stabilizing factor VIII within the plasma. This is why patients with vWD often have a mildly prolonged aPTT, as factor VIII is less stable and degraded at a faster rate.

vWD is characterized by both platelet abnormalities and a clotting factor deficiency (due to the role of vWF). The platelet defect can lead to minor bleeding events like epistaxis and bruising, while the clotting factor problem may result in more severe bleeding during procedures or menstruation.

Vitamin K is essential for the production of several clotting factors, including factors II, VII, IX, and X. In adults, vitamin K deficiency is often caused by prolonged antibiotic therapy, which disrupts the normal gut flora responsible for vitamin K synthesis.

Sickle cell anemia is a genetic condition caused by a specific mutation in the beta-globin gene. This mutation leads to the substitution of glutamic acid with valine at the sixth position of the beta-chain, causing the red blood cells to adopt a sickle shape.

Agranulocytosis is a severe reduction in neutrophils, a type of white blood cell essential for fighting infections. It can be a serious adverse effect of several medications, including clozapine (antipsychotic), ganciclovir (antiviral), propylthiouracil and methimazole (antithyroid), methotrexate (immunosuppressant), and ticlopidine (antiplatelet).

Febrile neutropenia (neutropenic fever) is a serious condition characterized by fever in patients with low neutrophil counts. It requires immediate treatment with broad-spectrum antibiotics, such as piperacillin/tazobactam or cefepime + vancomycin.