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Men who have sex with men
Men who have sex with men (MSM) is a behavioral public health category, coined in the early 1990s for HIV surveillance, covering men who have sex with men regardless of orientation; MSM bear 26 times higher HIV risk than the general population.
Menactra
Menactra (MenACWY-D, MCV4-D) is Sanofi Pasteur's quadrivalent meningococcal conjugate vaccine against N. meningitidis serogroups A, C, Y, W-135; first US conjugate license, January 2005, ages 9 months to 55 years.
Menadione
Menadione (2-methyl-1,4-naphthoquinone, vitamin K3) is a synthetic provitamin of vitamin K that the body converts to menaquinone; it is used mainly in animal feed and is toxic to humans.
MenAfriVac
MenAfriVac is an affordable meningococcal group A conjugate vaccine developed by the Serum Institute of India, introduced in 2010 and given to more than 350 million people across Africa's meningitis belt.
Menarche
Menarche, the first menstrual period, typically at ages 10–16 (mean ~12.4 y), 2–3 years after thelarche; driven by GnRH pulse reactivation; declining secular trend, contested plateau since 2000.
Menatetrenone
Menatetrenone (メナテトレノン), menaquinone-4 or MK-4, is a synthetic vitamin K2 drug (C31H40O2) sold as Glakay by Eisai; approved in Japan since 1995 at 45 mg/day for osteoporosis, it lowers undercarboxylated osteocalcin but shows uncertain fracture benefit.
MEND syndrome
MEND syndrome (male EBP disorder with neurological defects, OMIM 300960) is an X-linked recessive sterol biosynthesis disorder from hypomorphic EBP variants, causing ichthyosis, severe neurological defects, and dysmorphism in males, distinct from mosaic CDPX2.
Mendelson syndrome
Mendelson syndrome, or acid aspiration syndrome, is chemical pneumonitis from inhaling sterile gastric contents under anesthesia, first described by Curtis Mendelson in 1946 in obstetric patients; distinct from bacterial aspiration pneumonia.
Ménétrier disease
Ménétrier disease (giant hypertrophic gastritis, hypoproteinemic hypertrophic gastropathy) is a rare premalignant gastropathy with giant gastric folds, hypochlorhydria, and protein-losing enteropathy, driven by TGF-α/EGFR signaling; pediatric cases link to CMV.
Ménière's disease
Ménière's disease, an inner ear disorder with episodic vertigo, fluctuating hearing loss, tinnitus, and aural fullness, linked to endolymphatic hydrops; cause unknown, treated with diet, drugs, injections, or surgery.
Meningeal lymphatic vessels
Meningeal lymphatic vessels (MLVs), dural lymphatics rediscovered in 2015 by Louveau and Aspelund, drain CSF, interstitial fluid, waste, and immune cells to deep cervical lymph nodes; dysfunction links to Alzheimer's, Parkinson's, stroke, and aging.
Meninges
Meninges: the dura mater, arachnoid mater, and pia mater, the three membranes covering the brain and spinal cord, with their spaces, CSF, blood supply, and related conditions like meningitis and hematomas.
Meningioma
Meningioma, the most common primary brain tumor (37.6% of adult intracranial tumors), a slow-growing tumor of the meninges graded WHO 1-3, with TERT/CDKN2A/B molecular grading and treatment by observation, surgery, or radiosurgery.
Meningism
Meningism, also called meningismus, is the syndrome of headache, neck stiffness, and photophobia suggesting meningeal irritation when the meninges are not actually inflamed, so it requires evaluation to find the cause.
Meningitis
Meningitis is inflammation of the meninges, the lining of the brain and spinal cord, caused by bacteria, viruses, fungi, or parasites. Bacterial meningitis kills about 1 in 6 affected; the African meningitis belt bears the highest burden.
Meningitis due to adenovirus
Meningitis due to adenovirus (adenoviral meningitis, ICD-11 1C8E.2, ICD-10 A87.1) is a rare adenovirus infection of the meninges, spread hematogenously, causing fever, stiff neck, and headache, confirmed by CSF PCR.
Meningitis due to Cryptococcus neoformans
Meningitis due to Cryptococcus neoformans (cryptococcal meningitis): fungal CNS infection from inhaled C. neoformans, mainly in advanced HIV; diagnosed by CrAg and culture; treated with liposomal amphotericin B, flucytosine, fluconazole.
Meningitis due to Haemophilus influenzae
Meningitis due to Haemophilus influenzae (ICD-11 1D01.00), historically mainly Hib serotype b, was the leading cause of childhood bacterial meningitis before conjugate vaccines cut US cases by over 99%.
Meningitis due to mumps virus
Meningitis due to mumps virus is an aseptic meningitis caused when the mumps virus spreads to the membranes around the brain, occurring in up to 10% of unvaccinated mumps cases.
Meningitis due to Staphylococcus
Staphylococcal meningitis (ICD-11 1B54), bacterial meningitis from Staphylococcus aureus or epidermidis, usually after surgery or bloodstream spread; 4.9–6.4% of bacterial cases, mortality 14–50%, treated with vancomycin.
Meningitis due to Streptococcus
Meningitis due to Streptococcus (ICD-11 1B53), also called pneumococcal or streptococcal meningitis, is meningeal infection by Streptococcus, mainly S. pneumoniae and group B Streptococcus, with 24% pneumococcal case fatality.
Meningococcaemia
Meningococcaemia (meningococcemia, meningococcal septicaemia): bloodstream invasion by Neisseria meningitidis causing fever, purpuric rash, shock, and DIC; 10-15% case fatality, up to 40% in severe sepsis, treated with immediate parenteral antibiotics.
Meningococcal disease
Meningococcal disease, invasive infection by Neisseria meningitidis (meningococcus), causes bacterial meningitis and septicemia; six serogroups (A, B, C, W, X, Y) drive disease, with 10-15% case fatality and MenACWY/MenB vaccines for prevention.
Meningococcal groups a, b, c, w, and y vaccine
MenABCWY (pentavalent meningococcal groups A, B, C, W, and Y vaccine; Penbraya, Penmenvy) protects against five Neisseria meningitidis serogroups in people 10-25, used when both MenACWY and MenB vaccines are due at one visit.
Meningococcal vaccine
Meningococcal vaccine, also called MenACWY, MenB, or MenABCWY (Penbraya, Penmenvy), protects against Neisseria meningitidis serogroups A, B, C, W, and Y; conjugate vaccines replaced polysaccharide vaccines, cutting adolescent US disease over 90% since 2005.
Meningoencephalitis
Meningoencephalitis is simultaneous inflammation of the meninges and brain parenchyma, usually from viral, bacterial, or fungal infection. ICU mortality runs 11–25%; early acyclovir and cephalosporins improve outcomes; Naegleria fowleri causes a rare, nearly always fatal amebic form.
Meniscal allograft transplantation
Meniscal allograft transplantation is a surgical procedure replacing a damaged or missing knee meniscus with cadaveric donor tissue, offered mainly to younger patients with pain after meniscectomy.
Meniscal repair
Meniscal repair is an arthroscopic knee procedure that sutures a torn meniscus in place rather than removing it, preserving load-sharing tissue and slowing joint degeneration.
Meniscectomy
Meniscectomy is a surgical procedure that removes part or all of a damaged knee meniscus, most often arthroscopically, to relieve pain and mechanical symptoms like locking.
Meniscus (anatomy)
Meniscus (anatomy): the medial and lateral knee menisci, wedge-shaped fibrocartilage pads between femur and tibia that transmit load and absorb shock; vascular only peripherally, torn commonly, treated by repair or meniscectomy.