Medical terms, defined.

Median nerve palsy is loss of motor and/or sensory function of the median nerve (C5–T1), most commonly from carpal tunnel compression at the wrist or injury at the elbow/forearm. Classic signs are thenar atrophy, loss of thumb opposition...

Complete molar pregnancy is a gestational trophoblastic disease caused by fertilization of an empty ovum (no maternal DNA) by one sperm that duplicates (46,XX, all paternal) or, less often, two sperm (46,XY or XX). It produces diffuse hy...

Placenta percreta is the most severe form of placenta accreta spectrum (PAS), in which chorionic villi invade through the full thickness of the myometrium and penetrate the uterine serosa, sometimes into adjacent organs (e.g., bladder)....

Partial molar pregnancy is a form of gestational trophoblastic disease caused by fertilization of a single normal egg by two sperm (dispermy) or one sperm that duplicates, producing a triploid karyotype (69,XXY most common) with both fet...

Pilocytic astrocytoma is a benign (WHO grade 1) glial tumor, the most common primary brain tumor in children, typically arising in the cerebellum. It shows a biphasic pattern with Rosenthal fibers and eosinophilic granular bodies, often...

A nuchal cord is umbilical cord wrapped around the fetal neck, found in about 20–30% of term deliveries. Most cases are benign, but it can cause variable decelerations on fetal heart rate monitoring and, rarely, fetal hypoxia or neonatal...

Abruptio placentae is premature separation of a normally implanted placenta from the uterine wall before delivery (usually after 20 weeks), classically causing PAINFUL third-trimester vaginal bleeding with a firm, tender, tetanic uterus....

Breech presentation is a fetal malpresentation in which the buttocks or feet, rather than the head, are the presenting part at the pelvic inlet. It occurs in about 3-4% of term pregnancies and is far more common in preterm gestations. Ma...

Uterine inversion is a rare but life-threatening obstetric emergency in which the uterine fundus collapses into or through the endometrial cavity/cervix, most often in the third stage of labor. It presents with postpartum hemorrhage, sev...

Preterm premature rupture of membranes (PPROM) is spontaneous rupture of the fetal membranes (amniorrhexis) before 37 weeks' gestation and before the onset of labor. Major complications are preterm delivery, chorioamnionitis, umbilical c...

Hypoplastic left heart syndrome (HLHS) is a congenital cyanotic heart defect with underdevelopment of the left ventricle, mitral and aortic valves (stenosis/atresia), and ascending aorta/arch. Systemic circulation is entirely dependent o...

Specific phobia is an anxiety disorder characterized by marked, persistent, excessive fear of a particular object or situation (e.g., animals, heights, blood/injection, flying) that is almost always provoked on exposure, is out of propor...

Physiologic jaundice is a benign, transient unconjugated (indirect) hyperbilirubinemia affecting ~60% of term and ~80% of preterm newborns. It appears after 24 hours of life (typically day 2-3), peaks around day 3-5 in term infants (day...

Obsessive-Compulsive Disorder (OCD) is characterized by recurrent, intrusive, ego-dystonic obsessions (thoughts, urges, images) and/or compulsions (repetitive behaviors or mental acts) performed to reduce anxiety, which are time-consumin...

Body dysmorphic disorder (BDD) is a DSM-5 obsessive-compulsive and related disorder. The patient is preoccupied with perceived defects in physical appearance that are minimal or not observable to others. The preoccupation drives repetiti...

Acute stress disorder (ASD) is a trauma-related psychiatric disorder characterized by intrusion, dissociation, avoidance, negative mood, and arousal symptoms lasting 3 days to 1 month after exposure to actual or threatened death, serious...

Dysthymia (Persistent Depressive Disorder in DSM-5) is a chronic, low-grade depressed mood lasting ≥2 years in adults (≥1 year in children/adolescents), with depressed mood on most days and at least 2 additional depressive symptoms. Symp...

Hoarding disorder is a DSM-5 obsessive-compulsive and related disorder characterized by persistent difficulty discarding possessions regardless of their actual value, due to a perceived need to save them and distress associated with disc...

Cyclothymic disorder is a chronic mood disorder on the bipolar spectrum. It involves numerous periods of hypomanic symptoms and depressive symptoms that fail to meet full criteria for hypomanic or major depressive episodes. Symptoms last...

Bipolar II disorder is a mood disorder defined by at least one hypomanic episode (≥4 days) AND at least one major depressive episode (≥2 weeks), with NO history of a full manic episode. Depression dominates the clinical course, and patie...

MDD (Major Depressive Disorder) is a mood disorder defined by ≥2 weeks of depressed mood and/or anhedonia plus other symptoms (SIG E CAPS) causing functional impairment, without a history of mania or hypomania. First-line treatment is an...

Seasonal affective disorder (SAD) is a specifier of recurrent major depressive disorder (DSM-5: "with seasonal pattern") in which depressive episodes recur at a characteristic time of year, classically fall/winter with remission in sprin...

Premenstrual dysphoric disorder (PMDD) is a severe form of premenstrual syndrome classified as a depressive disorder in DSM-5. It involves marked mood symptoms (affective lability, irritability, depressed mood, anxiety) plus physical/beh...

Binge eating disorder (BED) is the most common eating disorder in the US. It is characterized by recurrent episodes of eating an excessive amount of food in a discrete period with a sense of lack of control, WITHOUT regular compensatory...

Alcohol withdrawal is a hyperadrenergic, CNS-hyperexcitable state after abrupt cessation or reduction of chronic heavy alcohol use, due to loss of GABA-A inhibition and unopposed NMDA/glutamate excitation. It ranges from mild tremor and...

Illness anxiety disorder (formerly hypochondriasis) is a preoccupation with having or acquiring a serious illness for ≥6 months, with minimal or no somatic symptoms and high health-related anxiety. Patients either seek care excessively (...

Substance use disorder (SUD) is a DSM-5 diagnosis defined by a problematic pattern of use of a substance (alcohol, opioids, stimulants, cannabis, sedatives, tobacco, etc.) causing clinically significant impairment or distress, with ≥2 of...

Histrionic personality disorder (HPD) is a Cluster B personality disorder characterized by pervasive excessive emotionality and attention-seeking behavior. Patients are dramatic, seductive, and uncomfortable when not the center of attent...

Narcissistic personality disorder (NPD) is a Cluster B personality disorder characterized by a pervasive pattern of grandiosity, need for admiration, and lack of empathy, beginning by early adulthood. Patients have fragile self-esteem, a...

Schizoid personality disorder (Cluster A, "odd/eccentric") is a pervasive pattern of detachment from social relationships and restricted emotional expression, with no desire for close relationships. Patients are loners who appear indiffe...

Dependent personality disorder (DPD) is a Cluster C ("anxious/fearful") personality disorder marked by a pervasive, excessive need to be taken care of, leading to submissive, clingy behavior and fear of separation. Patients struggle to m...

Functional neurological symptom disorder (FNSD; conversion disorder) is a DSM-5 diagnosis in which patients have one or more neurologic symptoms (weakness, paralysis, abnormal movements, seizures, sensory loss, speech or gait disturbance...

Avoidant personality disorder (AvPD) is a Cluster C ("anxious/fearful") personality disorder marked by lifelong social inhibition, feelings of inadequacy, and hypersensitivity to negative evaluation. Patients desperately WANT relationshi...

Obsessive-compulsive personality disorder (OCPD) is a Cluster C personality disorder marked by a pervasive preoccupation with orderliness, perfectionism, and control at the expense of flexibility and efficiency. Patients are ego-syntonic...

Schizotypal personality disorder (SPD) is a Cluster A ("odd/eccentric") personality disorder marked by social deficits, eccentric behavior, odd beliefs (magical thinking), unusual perceptual experiences, and cognitive/perceptual distorti...

Paranoid personality disorder (PPD) is a Cluster A ("odd/eccentric") personality disorder characterized by pervasive distrust and suspiciousness of others, interpreting their motives as malevolent, without frank psychosis. Patients are e...

Conduct disorder is a childhood/adolescent psychiatric disorder characterized by a repetitive, persistent pattern of violating the basic rights of others or major age-appropriate societal norms (aggression to people/animals, property des...

Tic disorders are neurodevelopmental conditions (onset <18 yr) characterized by sudden, rapid, recurrent, nonrhythmic motor movements or vocalizations. Tourette disorder requires ≥2 motor tics and ≥1 vocal tic for >1 year; persistent (ch...

ADHD is a neurodevelopmental disorder marked by a persistent pattern of inattention and/or hyperactivity-impulsivity that interferes with functioning, with onset of symptoms before age 12 and presence in ≥2 settings (e.g., home and schoo...

Selective mutism is a childhood anxiety disorder in which a child consistently fails to speak in specific social situations (e.g., school) despite speaking normally in others (e.g., home). It must last ≥1 month (not limited to the first...

Separation anxiety disorder is a childhood-onset anxiety disorder with developmentally inappropriate, excessive fear or anxiety about separation from attachment figures (usually parents), lasting ≥4 weeks in children/adolescents (≥6 mont...

The LDL receptor (LDLR) is a cell-surface glycoprotein, most abundant on hepatocytes, that binds ApoB-100 (and ApoE) on LDL particles and mediates their clathrin-dependent endocytosis, clearing LDL cholesterol from plasma. Loss-of-functi...

Encopresis is repeated passage of feces into inappropriate places (e.g., underwear) by a child ≥4 years old, occurring at least once monthly for ≥3 months, not due to a medical condition (except constipation). Most commonly it is overflo...

Omega-3 fatty acids are polyunsaturated fatty acids with the first double bond at the third carbon from the methyl (omega) end. They include ALA (plant-derived, essential), and EPA and DHA (marine-derived). They lower triglycerides, are...

PCSK9 inhibitors (evolocumab, alirocumab; monoclonal antibodies, and inclisiran, a siRNA) block PCSK9-mediated degradation of hepatic LDL receptors, increasing LDL receptor recycling and lowering LDL-C by ~50-60%. They are used in hetero...

Reteplase is a recombinant, non-glycosylated deletion mutant of human tissue plasminogen activator (tPA) that converts plasminogen to plasmin, producing fibrinolysis. It is FDA-approved for acute ST-elevation myocardial infarction (STEMI...

Ticlopidine is a thienopyridine antiplatelet drug that irreversibly blocks the platelet P2Y12 ADP receptor, which inhibits ADP-induced expression of the GPIIb/IIIa receptor and platelet aggregation. It was used for stroke prevention and...

Sarilumab (Kevzara) is a fully human monoclonal antibody that blocks the interleukin-6 (IL-6) receptor (both membrane-bound and soluble IL-6Rα). It is used for moderate-to-severe rheumatoid arthritis after inadequate response to DMARDs,...

Aminocaproic acid is a synthetic lysine analog antifibrinolytic that competitively blocks lysine-binding sites on plasminogen/plasmin, preventing fibrin clot degradation. It is used to treat bleeding due to excessive fibrinolysis (e.g.,...

Tocilizumab is a humanized monoclonal antibody that blocks the IL-6 receptor (both soluble and membrane-bound). It is used for rheumatoid arthritis (after DMARD/TNF-inhibitor failure), giant cell arteritis, systemic and polyarticular juv...