All articles starting with P
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Primary pericardial mesothelioma
Primary pericardial mesothelioma is a rare malignant tumor of the sac surrounding the heart, accounting for about 1% of mesotheliomas with median survival of 6 months.
Primary peritoneal carcinoma
Primary peritoneal carcinoma (PPC, ORPHA:168829), a rare extra-ovarian cancer of the peritoneum resembling serous ovarian carcinoma; about 10% of pelvic serous carcinomas, mean age 60, treated with cytoreductive surgery plus platinum chemotherapy.
Primary Prevention
Primary prevention: interventions that stop disease before it occurs by reducing causal exposures and raising resistance, through vaccination, smoking cessation, blood pressure control, and health promotion, distinct from secondary, tertiary, primordial, and quaternary prevention.
Primary production
Primary production, also called primary productivity, is the synthesis of organic matter from inorganic carbon by autotrophs through photosynthesis; global net production is about 104.9 petagrams of carbon per year.
Primary progressive aphasia
Primary progressive aphasia (PPA) is a neurodegenerative language-led dementia with three variants (nonfluent/agrammatic, semantic, logopenic), prevalence about 3 per 100,000, variant-linked survival of 7 to 12 years, and growing speech-therapy and TMS treatment evidence.
Primary progressive apraxia of speech
Primary progressive apraxia of speech (PPAOS) is a neurodegenerative tauopathy in which apraxia of speech is the first or only symptom, distinct from primary progressive aphasia, linked to PSP and corticobasal degeneration.
Primary progressive freezing gait
Primary progressive freezing gait (PPFG), also called primary progressive freezing of gait, is a rare adult-onset neurodegenerative syndrome with freezing of gait within 3 years, later falls and wheelchair dependence, unresponsive to levodopa, and caused by diverse pathologies including PSP and pallidonigroluysian degeneration.
Primary progressive multiple sclerosis
Primary progressive multiple sclerosis (PPMS) is a form of multiple sclerosis that worsens gradually from onset, without prominent relapses, affecting roughly 10 to 15 percent of people with MS.
Primary pulmonary hypoplasia
Primary pulmonary hypoplasia (idiopathic pulmonary hypoplasia, OMIM 265430) is a rare autosomal recessive congenital underdevelopment of lung tissue with no underlying disorder, usually lethal in newborns.
Primary pulmonary lymphoma
Primary pulmonary lymphoma (PPL), also called primary lung lymphoma or pulmonary MALT lymphoma, is a rare clonal lymphoid proliferation confined to the lungs, mostly low-grade MALT B-cell lymphoma, plus high-grade DLBCL and lymphomatoid granulomatosis, with no extrapulmonary disease for 3 months.
Primary pulmonary vein stenosis
Primary pulmonary vein stenosis (PPVS), also called congenital or idiopathic PVS, is progressive narrowing of the pulmonary veins without prior intervention, affecting infants, especially preterm babies with bronchopulmonary dysplasia, with high mortality and multimodality treatment.
Primary Rate Interface
The Primary Rate Interface (PRI) is an ISDN interface for businesses, providing 23 or 30 voice channels plus a signaling channel over a T1 or E1 line.
Primary Raynaud disease
Primary Raynaud disease (primary Raynaud's phenomenon, ICD-11 BD42.0) is idiopathic episodic vasospasm of digital arteries triggered by cold or stress, without underlying disease; it accounts for 80–90% of Raynaud cases, affects young women, and rarely progresses to tissue injury.
Primary retroperitoneal fibrosis
Primary (idiopathic) retroperitoneal fibrosis, Ormond's disease, is a rare fibroinflammatory periaortic mass encasing the ureters; largely IgG4-related, treated with glucocorticoids, tamoxifen, immunosuppressants, or ureterolysis.
Primary rhinoplasty
Primary rhinoplasty is the first surgical reshaping of the nose to improve its appearance and function, distinct from revision rhinoplasty, with major complications affecting less than 0.7% of patients.
Primary school
Primary school (primary education, ISCED level 1) is the first stage of formal schooling, teaching literacy and numeracy to children aged about 5-7 to 10-12, typically over six years with one main class teacher.
Primary schools in Scotland
Primary schools in Scotland are publicly funded schools taking children from Primary 1 at age 4 or 5 through Primary 7, run by 32 local authorities.
Primary sclerosing cholangitis
Primary sclerosing cholangitis (PSC) is a chronic liver disease in which inflammation and scarring narrow the bile ducts, leading to cirrhosis and often liver failure, treatable only by transplantation.
Primary source
A primary source is a first-hand record created by a participant in or witness to an event, including documents, diaries, letters, recordings, data, and artifacts; distinguished from secondary and tertiary sources, though classification depends on use and discipline.
Primary spermatocyte
Primary spermatocyte: diploid male germ cell in the seminiferous tubule, formed from B spermatogonia, that undergoes meiosis I (about 24 days in humans) to yield two haploid secondary spermatocytes; site of synapsis, recombination, and meiotic checkpoints.
Primary Stadium
Primary Stadium (成棒主球場) is the 25,000-seat adult-baseball main stadium of the Tainan Asia-Pacific International Baseball Training Center, Annan District, Tainan, Taiwan; Taiwan's largest outdoor baseball park and the Uni Lions' CPBL home since March 2026.
Primary standard
A primary standard is the top of the calibration hierarchy, established by a primary reference measurement procedure or chosen by convention, from which all other standards derive.
Primary succession
Primary succession: ecological community development on newly exposed, soil-free substrate such as glacier forelands or mining spoil, distinguished from secondary succession; sere, seral stages, relay floristics, facilitation, Glacier Bay 1,500-year sequence.
Primary superior vena cava aneurysm
Primary superior vena cava aneurysm (SVCA, ORPHA:652668, ICD-10 Q26.8) is a rare vascular anomaly, mostly fusiform and rarely saccular, of the SVC; usually asymptomatic, found incidentally on chest X-ray, managed conservatively if fusiform.
Primary surveillance radar
Primary surveillance radar (PSR) is an air traffic control sensor that detects aircraft by reflected radio pulses without any onboard equipment, providing range and azimuth but no altitude or identification.
Primary syphilis of other sites
Primary syphilis of other sites (ICD-11 1A61.2) is extragenital primary syphilis: a chancre at the mouth, lip, anus, rectum, or other non-genital inoculation site, often painless and unnoticed.
Primary syringomyelia
Primary syringomyelia, also called congenital syringomyelia (ICD-11 LA07.3), is a rare developmental malformation with a fluid-filled syrinx inside the spinal cord, causing cape-like pain and temperature loss and upper-limb-predominant weakness.
Primary tethered cord syndrome
Primary tethered cord syndrome (primary tethered spinal cord syndrome), a congenital low-lying, traction-fixed spinal cord with thickened filum terminale, causing progressive neurologic, musculoskeletal, and bladder/bowel symptoms; treated by surgical detethering.
Primary treatment (sewage)
Primary treatment is the first stage of sewage treatment, a physical, non-biological process in tanks that removes floating and settleable solids after screening and grit removal.
Primary ulcer of small intestine
Primary ulcer of small intestine (ICD-11 DA94.0, 原発性小腸潰瘍) is small bowel ulceration of unknown origin, also called simple, idiopathic, or nonspecific ulcer, including CMUSE and CNSU, presenting with anemia, bleeding, and strictures.