Metacarpophalangeal joint A condyloid synovial joint between each metacarpal head and proximal phalanx that enables finger movement, contributes to grip, and is commonly involved in trauma and inflammatory…
Metastasis (spread of cancer cells) Metastasis Metastasis is the process by which cancer cells leave a primary tumor and establish new tumors elsewhere. This article explains mechanisms, common sites, diagnosis, treatment appro…
Metastatic breast cancer Breast cancer that has spread beyond the breast and regional lymph nodes; overview of diagnosis, common treatments, goals of care, and distinctions including bone involvement and t…
Methadone: long‑acting synthetic opioid used for pain relief and addiction treatment Methadone Methadone is a long‑acting synthetic opioid used as an analgesic and as a maintenance medication for opioid use disorder; it has distinct pharmacology, benefits, and risks that req…
Methotrexate: uses, mechanism, monitoring, and safety Methotrexate Methotrexate is a folate‑antagonist drug used in oncology and as a disease‑modifying treatment for autoimmune disorders; it requires monitoring and is contraindicated in pregnancy.
Methylphenidate (Ritalin, Concerta): overview, effects, uses and risks Methylphenidate A concise encyclopedia entry on methylphenidate: what it is, how it works, clinical uses, formulations, common side effects, history, legal status and social concerns including mis…
Microsleep — brief involuntary sleep episodes and their risks Microsleep Microsleep are very short, involuntary sleep episodes during wakefulness. This article covers what they are, causes, signs, dangers (e.g., driving), detection, and ways to reduce r…
Midbrain (Mesencephalon): Structure, Function, and Clinical Significance Midbrain A concise encyclopedia entry on the midbrain (mesencephalon): its anatomy, major nuclei and pathways, development, roles in sensation and motor control, evolution, and clinical imp…
Middle finger (third digit of the human hand) Middle finger The middle finger is the third digit of the hand. This entry explains its anatomy, movements, common injuries, cultural meanings of the gesture, and historical origins.
Midwife: role, training, history, and practice Midwife A midwife assists women before, during, and after childbirth. This article outlines roles, types, training, practice settings, historical context, benefits, and how midwives relate…
Mifepristone (RU-486): overview, properties, uses and history Mifepristone Mifepristone is a synthetic antiprogestogen used mainly to terminate early pregnancy and for other medical indications. This article summarizes its actions, history, uses, safety a…
Migraine: symptoms, causes, types, and management Migraine A comprehensive overview of migraine disorder: typical symptoms (including aura), types (episodic vs chronic), underlying mechanisms, triggers, impact, and approaches to diagnosis…
Miscarriage: causes, signs, types, diagnosis and support Miscarriage Miscarriage (spontaneous abortion) is the loss of a pregnancy before the fetus can survive outside the womb. Overview of frequency, causes, types, diagnosis, treatment, and emotion…
Mitochondrial DNA depletion syndrome A group of rare autosomal recessive disorders in which reduced copies of mitochondrial DNA cause progressive failure of energy-dependent organs, typically presenting in infancy wit…
MMR vaccine: overview, schedule, safety, and public health importance MMR vaccine The MMR vaccine is a combined live attenuated vaccine that protects against measles, mumps and rubella. Two doses are highly effective and it is a key tool in preventing outbreaks…
Mobile Army Surgical Hospital (MASH): role, history and legacy Mobile Army Surgical Hospital Mobile Army Surgical Hospitals (MASH) were mobile frontline surgical units used by the U.S. Army from World War II through the Gulf War, noted for rapid trauma care, evacuation adv…
Mohel: the Jewish ritual circumciser Mohel A mohel is a practitioner trained to perform brit milah, the Jewish ritual circumcision. This article explains the mohel’s role, training, the ceremony, historical roots, variants,…
Moisturizer (skin-care product) Moisturizer A moisturizer is a topical formulation that helps maintain or restore skin hydration. This article explains how moisturizers work, common ingredients, product types, uses, and prac…
Monoamine oxidase inhibitor (MAOI) Monoamine oxidase inhibitor Monoamine oxidase inhibitors are antidepressant and neuropsychiatric agents that block MAO enzymes, used for certain depressions, Parkinson disease, and other indications; they req…
Monocle: single-eye optical lens and cultural symbol Monocle A monocle is a single corrective lens worn before one eye. Once common in the 19th and early 20th centuries, it served practical vision needs and later became a cultural and stylis…
Mononucleosis (infectious mononucleosis) Mononucleosis Infectious mononucleosis is an acute viral illness most often caused by Epstein–Barr virus, marked by fever, sore throat, swollen lymph nodes, fatigue, and atypical lymphocytes on…
Mood disorder (affective disorder) Mood disorder Mood disorders are mental health conditions marked by persistent changes in mood or emotional state, including depressive disorders and bipolar disorder; they affect functioning an…
Mood stabilizer (psychiatric medication) Mood stabilizer Class of psychiatric drugs used to treat mood disorders such as bipolar disorder; includes lithium and several anticonvulsants and atypical antipsychotics to control mania, depress…
Morning wood (nocturnal penile tumescence) Morning wood Morning wood, medically called nocturnal penile tumescence, is the spontaneous erection of the penis during sleep or on waking. It is a normal physiological phenomenon with diagnos…
Morphine: the prototypical opioid analgesic — properties, uses, risks Morphine Morphine is the chief active alkaloid of opium and a standard opioid analgesic. This article covers its pharmacology, clinical uses, adverse effects, history and distinctions from…
Morquio syndrome (Mucopolysaccharidosis type IV) — overview and management Morquio syndrome Rare inherited lysosomal disorder causing progressive skeletal and connective‑tissue abnormalities (MPS IV). Covers causes, features, diagnosis, treatments including enzyme replace…
Motor neurone disease (MND): causes, symptoms, diagnosis, and care Motor neurone disease Progressive neurological condition that destroys motor neurons. Covers types (including ALS), symptoms, causes, diagnosis, treatment approaches, prognosis, and important distinctio…
MRSA (Methicillin-resistant Staphylococcus aureus) MRSA An overview of MRSA: a strain of Staphylococcus aureus resistant to many beta-lactam antibiotics, its clinical features, resistance mechanisms, diagnosis, treatment, prevention, an…
Multiple myeloma: overview, diagnosis, treatment, and key facts Multiple myeloma Multiple myeloma is a cancer of plasma cells that affects bone, kidney and immunity. This article explains features, diagnosis, common treatments, supportive care, and related cond…
Multiple sclerosis — autoimmune demyelinating disease of the central nervous system Multiple sclerosis Multiple sclerosis (MS) is a chronic neurological disorder in which the immune system damages myelin in the central nervous system, producing variable neurological symptoms and a c…
Multiple system atrophy (MSA) Multiple system atrophy A rare, progressive neurodegenerative disorder causing autonomic failure, parkinsonism, and/or cerebellar ataxia; diagnosis is clinical, treatment symptomatic, and prognosis guarde…
Multivitamin — composition, uses, history, regulation and safety Multivitamin Overview of multivitamins: composition, common forms, intended uses, regulatory context, evidence on benefits, safety considerations and advice for consumers and specific groups.
Mumps (viral infection) Mumps Mumps is an acute viral infection that mainly affects the salivary glands in humans. It causes parotitis, fever and malaise, can lead to complications such as orchitis or meningiti…
Murine typhus (endemic typhus): causes, symptoms, diagnosis, and prevention Murine typhus Murine (endemic) typhus is a flea-borne bacterial infection caused by Rickettsia typhi. This article summarizes causes, symptoms, diagnosis, treatment, prevention, and distinctions…
Muscle atrophy: causes, types, mechanisms, diagnosis and management Muscle atrophy Muscle atrophy is loss of skeletal muscle mass and strength from disuse, aging, disease or nerve injury. This article explains types, underlying mechanisms, clinical impact, diagno…
Muscular dystrophy Muscular dystrophy refers to a group of inherited disorders that progressively weaken skeletal muscles. This article summarizes causes, major types, symptoms, diagnosis, management…
Mutilation: Definition, Causes, Consequences and Context Mutilation An overview of mutilation: what it is, common causes and types, physical and psychological effects, cultural and legal contexts, distinctions from medical amputation, and typical r…
Myalgia: causes, symptoms, diagnosis, and management Myalgia Myalgia is muscle pain that can arise from overuse, infection, systemic disease, medication, or injury. This article explains causes, symptoms, evaluation, treatment, and when to s…
Myasthenia gravis: causes, symptoms, diagnosis and treatment Myasthenia gravis A concise overview of myasthenia gravis: an autoimmune disorder of the neuromuscular junction causing fluctuating muscle weakness, its typical features, diagnostic approaches, and…
Mycobacterium tuberculosis — the bacterium that causes tuberculosis Mycobacterium tuberculosis Slow-growing, acid-fast bacterium that causes tuberculosis. Covers biology, history, transmission, clinical features, diagnosis, treatment, drug resistance, and public health impor…
Myelodysplastic Syndrome (MDS) Myelodysplastic syndrome Myelodysplastic syndromes are a group of bone marrow disorders that impair blood cell production, cause cytopenias, and carry a variable risk of progression to acute leukemia. Diag…
Myocarditis (inflammatory cardiomyopathy): causes, symptoms, diagnosis, treatment Myocarditis Myocarditis is inflammation of the heart muscle from infection, immune causes, or toxins. Symptoms vary from mild chest pain to heart failure or sudden cardiac arrest; diagnosis an…
Myopathy: causes, symptoms, diagnosis, and treatment of muscle disease Myopathy Myopathy refers to disorders in which muscle fibers themselves malfunction, causing weakness and related symptoms. This article covers types, signs, evaluation, treatment, and dist…
Myopia (Near-sightedness): Causes, Symptoms, Treatment, and Prevention Myopia Myopia (near-sightedness) is a common refractive condition causing blurry distance vision. This article covers causes, signs, diagnosis, treatment options, prevention strategies, c…
Naloxone — life‑saving opioid antagonist used to reverse overdoses Naloxone Naloxone is an opioid antagonist that rapidly reverses respiratory depression from opioid overdose. Available in injectable and nasal forms, it is widely used in emergency and comm…
Naltrexone — opioid receptor antagonist for alcohol and opioid dependence Naltrexone Naltrexone is an opioid receptor antagonist used to reduce alcohol cravings and block opioid effects. Available as daily oral tablets and a monthly injectable formulation; used aft…
Narcolepsy: causes, symptoms, diagnosis, and management Narcolepsy Narcolepsy is a chronic neurological sleep disorder causing excessive daytime sleepiness and, in many cases, cataplexy. This article explains signs, causes, diagnosis, treatment an…
Narcotic: meaning, history, medical use, and legal distinctions Narcotic Comprehensive overview of 'narcotic': historical origins, pharmacology, medical roles, risks of dependence and overdose, and why legal uses of the term are inconsistent.
