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The Coronavirus Song (COVID-19)

Overview Coronavirus disease (COVID-19) is an infectious disease caused by a newly discovered coronavirus. Most people infected with the COVID-19 virus will experience mild to moderate respiratory illness and recover without requiring special treatment.  Older people,...

Guillain-Barré Syndrome (Animation)

Overview Guillain-Barré syndrome (GBS) is an acute, inflammatory demyelinating polyneuropathy with ascending muscle weakness that is autoimmune in nature Clinical and epidemiological evidence seems to indicate that most cases are preceded by an infection such as...

Spondylolysis vs. Spondylolisthesis

Spondylolysis Defect or stress fracture of the pars interarticularis May be unilateral or bilateral Most common location is L5 of the lower lumbar spine X-rays: AP, lateral, and oblique views “Scottie Dog” sign on x-ray (fracture site is the collar) Seen on posterior...

Leukoplakia vs. Oral Candidiasis

Oral Leukoplakia Flat, white lesions that cannot be brushed from the oral mucosa Typically painless Associated with tobacco and alcohol use Associated with squamous cell carcinoma Erythroplakia: similar lesions, but with a red appearance Carry a higher risk of...

Retinal Detachment

General Retinal detachment is a separation of the neurosensory retina from the underlying retinal pigment epithelium and choroid Ophthalmogic emergency: without correction, permanent vision loss may occur in affected neurons Types Rhegmatogenous (most common type):...

Brown-Séquard Syndrome

General Features Brown-Séquard syndrome occurs due to lateral hemisection of the spinal cord Unilateral involvement of the dorsal column, corticospinal tract, and spinothalamic tract Causes of spinal cord hemisection include penetrating trauma from a stab, bullet, or...

Heparin-induced thrombocytopenia

General Features Heparin-induced thrombocytopenia (HIT) is an immune mediated disorder resulting from exposure to heparin May result in loss of limb or life Typical onset 5-10 days after heparin exposure Caused by IgG antibodies formed in response to complexes of...

Polymyositis vs. Dermatomyositis (Audiovisual Medcomic)

General Features Inflammatory myopathies with symmetric proximal weakness Involves muscle fiber destruction and inflammatory infiltration of muscles May cause patients trouble rising from chairs, climbing stairs, and combing hair Myalgias Occur more frequently in...

Urinary Casts

Features Cylindrical structures Composed of Tamm-Horsfall mucoprotein Formed in the tubular lumen of the distal nephron Some casts are benign while others may indicate significant renal disease Casts are characterized by the types of cells or elements which they...

Hereditary Hemochromatosis vs. Wilson Disease

General Features Hereditary hemochromatosis: disorder of iron overload Accumulation of iron resulting in toxicity of the liver, pancreas, joints, skin, heart, and endocrine organs Wilson disease (hepatolenticular degeneration): disorder of copper overload Accumulation...

Pleural Effusions: Transudate vs. Exudate

Classifying Pleural Effusions A pleural effusion is an accumulation of fluid within the pleural space Determining the underlying cause is facilitated by thoracentesis and pleural fluid analysis The pleural fluid may be classified as a transudate or an exudate,...

Pterygium vs. Pinguecula

Pterygium: fleshy triangular mass that extends to the cornea. May interfere with vision. Pinguecula: yellowish elevated bump or patch that does not grow across the cornea. Treatment is not usually necessary but can be resected. Both are conjunctival...

Epistaxis

Epistaxis may be classified as anterior or posterior nosebleeds. Anterior nosebleeds are most common, usually occurring at Kiesselbach’s plexus in the anterior nasal septum. Kiesselbach's plexus consists of the anterior ethmoid, greater palatine, sphenopalatine, and...

Porcelain Gallbladder vs. Courvoisier’s Gallbladder

Porcelain gallbladder: calcified gallbladder on abdominal radiograph due to scarring caused by chronic cholelithiasis/cholecystitis. Requires cholecystectomy due to association with gallbladder carcinoma. Courvoisier's gallbladder: enlarged, palpable nontender...

Preeclampsia: Pathophysiology

General Features Preeclampsia is classically defined as the new onset of hypertension and proteinuria after 20 weeks of gestation. New onset hypertension with significant end-organ dysfunction (with or without proteinuria) after 20 weeks of gestation also satisfies...

Acute Sinusitis

General Features Acute sinusitis is an inflammation of the paranasal sinuses usually due to a viral infection, but secondary bacterial infection can occur. Often precipitated by an upper respiratory infection. Inflammation causes swelling of the mucosa leading to...

The Hypothalamic-pituitary-adrenal Axis

The Adrenal Glands The adrenal glands are triangular shaped organs that sit on top of the kidneys. Each adrenal gland is composed of an outer portion called the cortex, and an inner portion called the medulla. The adrenal cortex secretes...

Acoustic Neuroma (Vestibular Schwannoma)

General Features An acoustic neuroma is a benign Schwann cell-derived tumor of the eighth cranial nerve. Also known as a vestibular schwannoma. Usually unilateral In neurofibromatosis type 2, acoustic neuromas are typically bilateral. Signs and Symptoms...

Monteggia vs. Galeazzi Fractures

Definitions A Monteggia fracture is a fracture of the proximal ulna with dislocation of the radial head. There are four types, based on the direction that the radial head is displaced (Bado classification). A Galeazzi fracture is a fracture of the distal...

Heart Failure: Systolic vs. Diastolic Dysfunction

General Considerations Heart failure­ is defined as the inability of the heart to provide sufficient output to meet the metabolic demands of the body. Heart failure may be classified by symptom severity (NYHA classification) and by stage of evolution...

Functional Classification of Heart Failure

Functional Classification Systems The New York Heart Association (NYHA) functional classification is based on the amount of activity needed to elicit symptoms from the patient. The American College of Cardiology/American Heart Association...

Heart Failure: Pathophysiology

General Features and Pathophysiology Heart failure (HF)­ is defined as the inability of the heart to provide sufficient output to meet the metabolic demands of the body. Most often a chronic condition, but may also be acute. Heart failure leads to tissue...

Hodgkin Lymphoma

Hodgkin lymphoma (HL) is a clonal B-cell malignancy that resides predominantly in the lymphatic system. HL tends to develop within a single lymph node region and spreads in an orderly fashion to adjacent lymph nodes. A defining characteristic of HL is the presence of...

Typical Community Acquired Pneumonia

Community acquired pneumonia (CAP) is an acute infection of the lung parenchyma acquired outside of the hospital or less than 48 hours after hospital admission. CAP is classified into typical and atypical subtypes, differentiated by their presentation and causative...

Visual Release Hallucinations (Charles Bonnet syndrome)

Visual release hallucinations, also known as Charles Bonnet syndrome (CBS), refers to symptoms of visual hallucinations that occur due to vision loss from any underlying cause. The underlying condition may affect the eye, optic nerve, or the brain. Examples of...

Pityriasis Rosea

Pityriasis rosea is an acute, self-limited eruption of oval, scaly papules and plaques with a distinctive morphology. Females are affected more often than males, and it most common in teenagers and young adults. Pityriasis rosea peaks in the spring and fall seasons....

Clostridium difficile Infection

Clostridium difficile is a gram-positive anaerobic bacillus which secretes toxins (A and B) that cause diarrhea and pseudomembranous colitis. C. difficile is the most common infectious cause of nosocomial diarrhea. Transmission of C. difficile can occur from contact...

Obsessive-Compulsive Disorder

Obsessive-compulsive disorder (OCD) is characterized by recurrent, intrusive, undesired thoughts (known as obsessions) and/or uncontrollable repetitive acts (known as compulsions). Obsessions and compulsions are time-consuming (> 1 hour in a day), and cause...

The Menstrual Cycle

The menstrual cycle is coordinated by a series of hormones that regulate the growth of the endometrium, the development of an oocyte, release and possible implantation of an ovum, and if pregnancy does not occur, sloughing of the endometrium and menses to allow a...

Pulmonary Hypertension

Pulmonary hypertension (PH) refers to increased pressure in the pulmonary circulation. It develops when pulmonary vessels become constricted and/or obstructed, which can occur in a wide variety of conditions. The increase in pressure is measured by right...

Medulloblastoma

Medulloblastoma is the most common type of malignant brain tumor in childhood. It is an aggressive solid tumor malignancy that develops in the posterior fossa, which contains the brain stem and cerebellum. Boys are affected more frequently than girls, with...

Testicular Torsion

Testicular torsion occurs when the spermatic cord twists within the tunica vaginalis, resulting in ischemia to the epididymis and the testis. Testicular torsion may occur in the absence of a preceding event or after minor trauma. Patients typically experience acute...

Aortic Stenosis

Causes of aortic stenosis (AS) include degenerative sclerosis with calcification of a trileaflet aortic valve, calcification of a congenital aortic bicuspid valve, or rheumatic fever. Narrowing of the aortic valve obstructs blood flow from the left ventricle to the...

Graves’ Disease

Graves’ disease is an autoimmune disorder that results in the overproduction of thyroid hormones. It is the most common cause of hyperthyroidism. Women 20 to 40 years of age are typically affected. Thyrotoxicosis may cause unexplained weight loss due to an...

Wound Closure

The three types of wound healing: 1. Primary intention - the wound closed immediately in some manner (e.g. suture, Steri-Strips, staples, glue) 2. Secondary intention - the wound is left open and allowed to heal by granulation, epithelialization, and contraction. 3....

CREST Syndrome

CREST syndrome (limited cutaneous systemic sclerosis): Calcinosis: calcium deposits in the skin and tissues. Raynaud’s phenomenon: an exaggerated vascular response to cold temperature or emotional stress which may manifest as white-blue-red transitions in skin color....

Rhabdomyolysis

Rhabdomyolysis is the breakdown of muscle tissue with release of intracellular contents such as myoglobin into the bloodstream. The condition usually follows major muscle trauma, especially a crush injury. It can also be caused by long-distance running, hyperthermia,...

Colles’ Fracture

A colles' fracture is a fracture of the distal radius with dorsal angulation. The majority of these injuries demonstrate a "dinner fork" deformity. All displaced fractures should undergo closed reduction, which helps limit swelling, pain, and compression on the median...

Renal Tubular Acidosis

Renal tubular acidosis (RTA) refers to a group of disorders affecting the renal tubules characterized by an impaired ability to acidify the urine and excrete acid. The condition results in a hyperchloremic metabolic acidosis with a normal serum anion gap. Type 1...

Heart Sounds

The first heart sound (S1) represents mitral and tricuspid valve closure as the ventricular pressure exceeds atrial pressure at the beginning of systole. The second heart sound (S2) represents aortic and pulmonary valve closure at the end of systole/beginning of...

Horner Syndrome

Horner syndrome results from disruption of the sympathetic pathway that runs from the hypothalamus to the eye. Classic signs include miosis, ptosis, and anhidrosis of the affected side. Causes include brain tumor, brain stem infarct, pancoast tumor, cervical...

Salter-Harris Fractures

Pediatric physeal fractures have traditionally been described by the five-part Salter-Harris classification system. Type I fractures occur through the growth plate. These injuries may present with normal radiographs and the diagnosis is often made clinically when...

Abnormal structures in Alzheimer’s disease

Alzheimer's disease (AD) is a neurodegenerative disorder and the most common cause of dementia. Neurons communicate via chemical messages passed between two cells across a small gap called a synapse. In AD, abnormal cellular structures lead to a loss of synapses and...

Cardiac Tamponade

Cardiac tamponade is an accumulation of fluid in the pericardial sac that compresses the heart, impairs diastolic filling, and leads to a reduction in cardiac output. Tamponade is most often caused by penetrating trauma. Other causes of acute cardiac tamponade include...

Avoid poor rapport

People can sense when you're in a rush or focusing too much on an electronic health record (EHR). We must appreciate the importance of bedside manner and establishing trust with patients. Compassion is often more effective than a quick Z-pack. Based on personal...

Scoliosis and the Cobb Angle

Scoliosisis a lateral curvature of the spine. Adolescent idiopathic scoliosis is the most common type of scoliosis which typically has an onset after 10 years of age. The degree of curvature of the spine is determined by the Cobb angle. A curve with a Cobb angle ≥ 10...

Sensory Supply to the Hand

The ulnar nerve supplies half of the fourth digit and the entire fifth digit on the dorsal and palmar aspects of the hand. The ulnar nerve supply extends proximally to the wrist. Dorsally, the median nerve supplies the tips of the first, second and third digits, as...

Chickenpox vs. Shingles

The varicella-zoster virus causes varicella (chickenpox) and shingles (herpes zoster). It is very contagious. Chickenpox is usually a childhood infection that begins with a prodrome of fever, headache, and malaise followed by a generalized vesicular rash. It is...

Ectopic Pregnancy

In ectopic pregnancy, implantation occurs outside of the uterus. The most common site is the fallopian tube, but other possible sites include the pelvic or abdominal cavity, uterine cornu, cervix, or ovary. Risk factors include previous ectopic pregnancy, history of...

Barrett Esophagus

Barrett esophagus is a condition in which intestinal metaplastic columnar epithelium replaces the stratified squamous epithelium that normally lines the distal esophagus. The condition develops as a consequence of chronic gastroesophageal reflux disease (GERD) due to...

Normal Pressure Hydrocephalus

Normal pressure hydrocephalus (NPH) is a gradual accumulation of cerebrospinal fluid (CSF) that causes the ventricles of the brain to enlarge. The condition occurs with a normal or slightly elevated CSF pressure. NPH is characterized by a classic triad of dementia,...

Wolff–Parkinson–White syndrome

Wolff-Parkinson-White syndrome (WPW) is a pre-excitation syndrome of intermittent tachycardia that results from an accessory pathway (the bundle of Kent) directly connecting the atria and the ventricles. The anomalous pathway allows electrical activity to bypass the...

Pen the Doctor Borrowed (PTDB)

Pen the Doctor Borrowed (PTDB) is a condition that occurs when a student loans their pen to a preceptor and never sees it returned. Common symptoms include anxiety, diaphoresis, and decreased funds due to new pen purchases. PTDB affects millions of students every day....

Types of Jaundice

Jaundice is a yellow discoloration of the skin and mucous membranes caused by an excess accumulation of bilirubin in the blood. Bilirubin (a tetrapyrrole) is a product of red blood cell (RBC) breakdown. Jaundice becomes visible when the bilirubin level is...

Scabies

Scabies is an infestation of the skin by the Sarcoptes scabiei mite. It causes generalized intractable pruritus with a characteristic distribution pattern. Risk factors include immunosuppression and crowded living conditions. Scabies is easily transmitted through skin...

Fibrocystic Changes vs. Fibroadenoma

Fibrocystic changes (previously known as fibrocystic disease) is a benign breast condition consisting of fibrous (rubbery) and cystic changes in the breast. It's a catchall term that refers to wide variety of benign histologic changes in the breast epithelium. The...

Dental Caries (cavities)

Dental caries (cavities) is tooth decay caused by bacteria in dental plaque. Streptococcus mutans is a gram positive, anaerobic bacterium that causes caries. Pain occurs as the caries progress. Left untreated, caries lead to tooth destruction, infection, and loss of...

The Abnormal Prostate

Nonbacterial prostatitis is the most common of the prostatitis syndromes. Its mechanism is unknown and is a diagnosis of exclusion. Acute bacterial prostatitis is usually caused by gram-negative pathogens found in other urinary infections and less commonly by...

Abdominal Aortic Aneurysm

An abdominal aortic aneurysm (AAA, or “triple A”) is an abnormal dilation of the abdominal aorta, usually due to atherosclerosis. An aneurysm is considered to be present when the diameter exceeds 3 cm and the most common site is the infrarenal aorta. Risk factors...

Tension Pneumothorax

Tension pneumothorax develops as air accumulates in the pleural space, compresses the lung, and shifts the mediastinum. The air that enters the pleural space is trapped and cannot escape during expiration. Tension pneumothorax typically occurs due to a lung or chest...

Multiple Sclerosis

Although the exact cause of multiple sclerosis (MS) is unknown, the disease is thought to occur as an immune-mediated attack on the central nervous system (CNS). The condition causes inflammation, demyelination, and axonal degeneration that can manifest through a wide...

Orthopedic Emergencies

Major orthopedic emergencies involve limb or life-threatening conditions. We can identify some of these conditions in a biker who has, unfortunately, been involved in a motorcycle accident. Look for: 1. Open fractures and dislocations 2. Hip dislocations (risk of AVN)...

Chronic Myelogenous Leukemia

Chronic Myelogenous Leukemia (CML) is a myeloproliferative disease characterized by proliferation of myeloid cells capable of differentiation. CML is caused by a reciprocal translocation t(9;22), in which a piece of chromosome 9 containing the ABL1...

Appendicitis

Appendicitis is the most common cause of abdominal pain requiring surgical intervention. It is usually caused by an obstruction of the appendiceal lumen due to fecaliths or lymphoid hyperplasia. Patients may experience sharp periumbilical pain that moves to the right...

Basal Cell Carcinoma vs. Squamous Cell Carcinoma

BCC is the most common type of skin cancer and occurs in sun-exposed areas. SCC may occur on any skin surface, but is also most commonly seen on sun-exposed areas. SCC may arise from actinic keratoses and sites of chronic wounds or scarring. SCC is more common and...

Adventitious Breath Sounds

Adventitious breath sounds are abnormal sounds that are superimposed over normal breath sounds. Detection of these sounds can aid in the diagnosis of various pulmonary and cardiac conditions. Crackles (Rales) are discontinuous, intermittent, “popping” sounds. Fine...

Acute Myelogenous Leukemia

Acute Myelogenous Leukemia (AML) is the most common acute leukemia in adults. Most patients are over 65 years of age and the incidence increases with advanced age. AML is characterized by the sludging of blasts in the microvasculature due to leukostasis...

Statins

Statins (HMG-CoA reductase inhibitors) are the most effective drugs available for lowering LDL cholesterol, with reductions in the range of 30 to 60 percent. They also reduce levels of VLDL and increase levels of HDL. In addition, statins are used in the primary and...

Stages of Chronic Kidney Disease

Chronic kidney disease (CKD) is progressive and irreversible. It is defined as either kidney damage or a GFR of < 60 mL/min/1.73 m² for 3 or more months. The most common causes of CKD are diabetes mellitus (DM) and hypertension (HTN). Other causes include recurrent...

Zika Virus Infection

Zika Virus Infection is typically caused by the bite of an infected Aedes species mosquito (A. aegypti and A. albopictus). These mosquitoes also transmit the dengue and chikungunya viruses. Spread of the Zika virus through blood transfusion and sexual contact has also...

Type 1 Diabetes Mellitus

This post is dedicated to my little niece, named Coral, who lives with type 1 diabetes. She's also the star of the comic! Type 1 Diabetes Mellitus (DM) occurs due to pancreatic beta cell destruction leading to an absence of insulin production. It most commonly...

Naegele’s Rule

The due date or expected date of confinement (EDC) can be calculated using Naegele's Rule. Begin on the first day of the last menstrual period (LMP), subtract 3 months, add 7 days, and then add 1 year. Example LMP: February 14, 2015 Subtract 3 months (Great Scott x...

Holiday Heart Syndrome

Holiday Heart Syndrome (HHS) describes the occurrence of an acute cardiac arrhythmia after an episode of acute alcohol excess or alcohol withdrawal. The condition may also occur in predisposed individuals that consume a small amount of alcohol. The name of the...

Acute Lymphoblastic Leukemia

Acute Lymphoblastic Leukemia (ALL) is the most common cancer in children, but it can also occur in adults of all ages. There is a bimodal distribution, with peaks at 3-7 years and 65 years of age. The clinical presentation of ALL is nonspecific: fever,...

Ehlers-Danlos Syndrome

Ehlers-Danlos syndrome (EDS) is a rare hereditary disorder that results in skin hyperextensibility, joint hypermobility, and tissue fragility. This syndrome is caused by a gene defect which results in faulty collagen synthesis. Patients may experience debilitating...

The Femur

The femur is found in the upper leg and is the longest bone in the body. The femur articulates proximally with the acetabulum of the pelvis to form the hip joint, and distally with the tibia and patella to form the knee joint.

Chronic Lymphocytic Leukemia

Chronic Lymphocytic Leukemia (CLL) is the monoclonal proliferation of malignant B lymphocytes. It is the most common adult leukemia in Western countries, accounting for 30% of all cases in the United States. CLL typically affects adults greater than 65...

Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetic disorder with autosomal-dominant in­heritance but variable penetrance. There is thickening of the left ventricle and septum. The disorder causes diastolic dysfunction and can result in a diverse clinical course including...

Barlow vs. Ortolani

The Barlow maneuver is a test used to identify an unstable hip that can be passively dislocated. The infant is placed in a supine position with the hip flexed to 90º and in neutral rotation. The examiner adducts the hip while applying a posterior force on the knee to...

Lung Volumes and Capacities

Lung volumes and capacities refer to the changes in lung volume during inspiration and expiration, and the absolute volume of air that the lungs hold during the respiratory cycle. These relationships are recorded using a device called a spirometer. The amount of air...

Cranial Nerves

The cranial nerves are numbered sequentially in relation to their position from the front of the brain to the back. There are 12 pairs of cranial nerves which emerge from the underside of the brain and pass through the foramina in the base of the skull. Cranial nerves...

Melanoma Recognition

Melanoma accounts for the majority of deaths resulting from skin cancer. It is an aggressive malignancy of the pigment-producing melanocytes. The “ugly duckling” sign characterizes a lesion that appears to be an outlier in the presence of similar-appearing moles. The...

Tetralogy of Fallot

Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart defect. The main components of TOF are pulmonary stenosis, right ventricular hypertrophy, an overriding aorta, and a ventricular septal defect. A helpful mnemonic to recall these features is...

Nephritic vs. Nephrotic Syndrome

Nephritic syndrome is characterized by inflammation of the glomeruli (glomerulonephritis) and renal dysfunction. The most common cause is immunoglobulin A (IgA) nephropathy, also known as Berger’s disease, but other causes include postinfectious glomerulonephritis and...

Acute Cholangitis

Acute cholangitis is a bacterial infection of the biliary tract that results from biliary obstruction. The organisms typically ascend from the duodenum. The most common cause is choledocholithiasis, although neoplasms, postoperative strictures, or other...