Human health and medicine

Passive smoking

Passive smoking, or secondhand smoke exposure, is inhaling tobacco smoke as a nonsmoker; about 85% sidestream smoke, no safe level, causes lung cancer, heart disease, stroke, and child respiratory illness, killing about 1.3 million people yearly.

Passive stretching

Passive stretching is a flexibility technique in which a therapist, gravity, or a device lengthens muscles and moves joints without active effort, used in rehabilitation and sports medicine.

Oct 20, 2026

Pasteurellosis

Pasteurellosis: infection with Pasteurella bacteria, chiefly Pasteurella multocida, a Gram-negative coccobacillus. Causes fowl cholera, haemorrhagic septicaemia (serotypes B:2/E:2), atrophic rhinitis, and human bite-wound infections.

PaSTo trial

PaSTo (NCT03167268), Panitumumab Skin Toxicity Prevention Trial: Italian phase 2 double-blind trial of oral lycopene 20 mg versus placebo to reduce panitumumab-induced skin toxicity in metastatic colorectal cancer; 28 enrolled, reported 41% absolute reduction of grade 2-3 toxicity.

Patch Adams

Patch Adams, born Hunter Doherty Adams, is an American physician and social activist who founded the Gesundheit! Institute, campaigning since the 1970s for free healthcare with humor.

Patch angioplasty

Patch angioplasty is a vascular surgery technique that widens a narrowed artery by sewing in a patch of vein, bovine pericardium, or synthetic material, chiefly after carotid endarterectomy.

Patch test

Patch test: epicutaneous diagnostic procedure for allergic contact dermatitis, devised by Josef Jadassohn in 1895; allergens applied under patches for 48 hours with delayed readings to detect T-cell mediated skin allergy.

Patch-sequencing

Patch-seq (Patch-sequencing) is a multimodal neuroscience technique combining patch-clamp electrophysiology, single-cell RNA sequencing, and morphology in the same neuron, first implemented reliably in 2016 and central to brain cell type atlases.

Patella

Patella (kneecap), largest sesamoid bone, embedded in the quadriceps tendon at the knee; increases quadriceps leverage (31% of extension torque at full extension), ossifies at age 5-6, prone to dislocation and fracture.

Patellar reflex

Patellar reflex (knee jerk, Patellarsehnenreflex): monosynaptic L2-L4 stretch reflex elicited by tapping the patellar tendon, causing quadriceps contraction; described by Erb and Westphal in 1875 and increasingly quantified with EMG and motion analysis.

Patellar tendinitis

Patellar tendinitis, also called patellar tendinopathy or jumper's knee, is a degenerative overuse injury of the tendon joining kneecap to shinbone, common in jumping athletes and treated first with staged tendon-loading exercise rather than surgery.

Patellofemoral disorders

Patellofemoral disorders are a group of conditions affecting the joint between the kneecap and femur, most commonly pain worsened by squatting, stair use, and running, treated with exercise therapy.

Patellofemoral pain syndrome

Patellofemoral pain syndrome (PFPS, runner's knee, chondromalacia patella): anterior knee pain around or behind the patella aggravated by squatting, stairs, or running; treated mainly with hip and quadriceps exercise therapy.

Patent ductus arteriosus

Patent ductus arteriosus (PDA), persistent ductus arteriosus: a congenital heart defect in which the fetal vessel joining aorta and pulmonary artery stays open after birth. Common in preterm infants; treated with indomethacin, ibuprofen, acetaminophen, or catheter/surgical closure; first surgically repaired by Robert Gross in 1938.

Patent foramen ovale

A patent foramen ovale is a flap-like opening between the heart's right and left atria that fails to seal after birth, present in about 25% of adults.

Patent medicine

Patent medicines were trademarked, secret-formula self-medication remedies, few actually patented, that flourished in 19th-century America; dangerous ingredients and cure-all claims drove the 1906 Pure Food and Drugs Act and modern drug regulation.

Patent urachus

Patent urachus, also called persistent urachus (Offener Urachus), is a congenital urachal anomaly in which the embryonic duct between bladder and umbilicus stays open, causing umbilical urine leakage in neonates.

Paternal uniparental disomy of chromosome 20 syndrome

Paternal uniparental disomy of chromosome 20 syndrome (UPD(20)pat): very rare anomaly where both chromosome 20 copies come from the father, causing overgrowth, macrocephaly, and pseudohypoparathyroidism type 1b via the imprinted GNAS locus.

Paternity testing

Paternity testing is a genetic test comparing DNA between a child and an alleged father to confirm or exclude paternity, used in legal, personal, and immigration cases.

Pathogen reduction (blood transfusion)

Pathogen reduction, also called pathogen inactivation, is a transfusion medicine treatment that damages pathogens' nucleic acids in donated platelets and plasma so they cannot transmit infection.

Pathogen transmission

Pathogen transmission, also called disease transmission, is the process by which an infectious agent spreads from a reservoir or infected host to a new susceptible person.

Pathogenesis of endometriosis

The pathogenesis of endometriosis is the set of contested mechanisms by which endometrium-like tissue grows outside the uterus, including retrograde menstruation, coelomic metaplasia, stem cell theories, and immune dysfunction.

Pathologic Complete Response

Pathologic complete response (pCR), or pathologic complete remission: no residual cancer found microscopically in surgical specimens after neoadjuvant therapy. Prognostic in breast, digestive, lung cancers; FDA accelerated-approval endpoint in breast cancer; weak trial-level surrogate.

Pathologica

Pathologica, Italian pathology journal founded 1908 in Genoa, official journal of SIAPEC-IAP, published open access by Pacini Editore, ISSN 0031-2983, indexed in Medline, Scopus, ESCI.

Pathological demand avoidance

Pathological demand avoidance (PDA), also called extreme demand avoidance, is a proposed autism profile marked by anxiety-driven avoidance of everyday demands and need for control; coined by Elizabeth Newson in the 1980s, it is not in DSM-5 or ICD-11 and its validity as a syndrome is debated.

Pathological fracture

Pathological fracture (pathologic fracture): a bone fracture through bone weakened by preexisting disease such as osteoporosis, tumors, or Paget's disease, occurring without adequate trauma; ICD-11 code FB80.B.

Pathological jealousy

Pathological jealousy, also called morbid jealousy, delusional jealousy, or Othello syndrome, is a psychiatric condition of unfounded preoccupation with a partner's infidelity, occurring in obsessive and delusional subtypes with neurological, psychiatric, and substance-related causes.