1,838 articles
Myotonia
Myotonia (ICD-11 MB47.9) is delayed muscle relaxation after contraction, from sarcolemmal ion-channel hyperexcitability. Seen in myotonic dystrophies DM1/DM2 and non-dystrophic myotonias such as myotonia congenita; diagnosed by EMG myotonic discharges and genetic testing.
Myotonic disorders
Myotonic disorders (myotonic syndromes) are inherited or acquired muscle disorders with delayed relaxation after contraction. They include myotonic dystrophy types 1 and 2 (Steinert disease, PROMM) and nondystrophic myotonias such as myotonia congenita.
Myotonic dystrophy
Myotonic dystrophy (Steinert's disease, DM1/DM2) is an autosomal dominant multisystem muscular dystrophy caused by CTG (DMPK) or CCTG (CNBP) repeat expansions producing toxic RNA that sequesters MBNL splicing factors; no approved disease-modifying therapy exists.
Myxofibrosarcoma
Myxofibrosarcoma (MFS), formerly myxoid malignant fibrous histiocytoma, is a malignant soft tissue sarcoma of the elderly, mainly in the extremities, with myxoid stroma, curvilinear vessels, high local recurrence (10–61%), and complex karyotype.
Naegeli-Franceschetti-Jadassohn syndrome
Naegeli-Franceschetti-Jadassohn syndrome (Naegeli syndrome, NFJS) is a rare autosomal dominant ectodermal dysplasia caused by KRT14 mutations, marked by absent fingerprints, reticulate hyperpigmentation that fades after puberty, hypohidrosis, and enamel defects.
Nail atrophy
Nail atrophy (ICD-11 EE10.4) is thinning or loss of the nail plate from nail matrix damage, chiefly nail lichen planus or the rare childhood entity idiopathic atrophy of the nails (Samman, 1969).
Nail clubbing
Nail clubbing, or Hippocratic fingers, is bulbous enlargement of the fingertips with loss of the normal nail-fold angle, defined by a Lovibond angle over 180 degrees, linked to lung, heart, and liver disease and first described by Hippocrates in empyema.
Nail disease
Nail disease (nail disorders, onychomycosis, paronychia, nail psoriasis) covers infections, trauma, inflammatory and systemic conditions of the nail unit; fungi cause about 50% of nail dystrophies, with mean onychomycosis prevalence 4.3% in Europe and the US.
Nail fragility
Nail fragility (brittle nails, brittle nail syndrome, ICD-11 EE13.0): nail plate splitting and crumbling affecting up to 20% of people, mostly women over 50; idiopathic or secondary; treated by cause, protection, and supplements.
Nail hypertrophy
Nail hypertrophy (甲肥厚, onychauxis), ICD-11 EE10.3, is acquired thickening or overgrowth of the nail plate, including pachyonychia, subungual hyperkeratosis, and onychogryphosis; caused by fungal infection, psoriasis, trauma, or genetic disease.
Nail pitting
Nail pitting: small (about 1 mm or less) depressions in the nail plate from defective keratinization of the proximal nail matrix. Also called pitted nails. Often idiopathic; otherwise linked to psoriasis, alopecia areata, eczema, lichen planus, trachyonychia, chemotherapy, or nail cosmetics.
Nail-patella syndrome
Nail-patella syndrome (Fong disease, Turner-Kieser syndrome, HOOD), a rare autosomal dominant LMX1B disorder with nail dysplasia, absent or hypoplastic patellae, elbow dysplasia, pathognomonic iliac horns, nephropathy, and glaucoma.
Nasal dermoid cyst
Nasal dermoid sinus cyst (NDSC), congenital midline nasal mass of children, incidence 1:20,000-40,000 births, ectodermal inclusion origin, may extend intracranially, MRI-based diagnosis, treated by surgical excision.
Native American myopathy
Native American myopathy, now called STAC3 disorder or Bailey-Bloch congenital myopathy, is an autosomal recessive congenital myopathy caused by STAC3 mutations, first described in the Lumbee tribe, with weakness, contractures, cleft palate, and malignant hyperthermia susceptibility.
Natural history and clinical course of Duchenne muscular dystrophy
The natural history of Duchenne muscular dystrophy runs from symptoms at ages 2 to 3, loss of walking by 8 to 12 untreated, and death in the twenties.
NC/Nga
NC/Nga (Nishiki-nezumi Cinnamon/Nagoya) is an inbred laboratory mouse strain from Japanese fancy mice that spontaneously develops atopic dermatitis-like skin lesions with high IgE under conventional, but not SPF, housing; the first AD mouse model.
Neck pain
Neck pain (cervicalgia): pain between the skull base, first thoracic vertebra, and trapezius insertions. Affects about 203 million people globally (2020); usually caused by posture, sleeping position, pinched nerve, or whiplash, and mostly improves with self-care in 2–3 weeks.
Necrobiosis lipoidica
Necrobiosis lipoidica (NLD, necrobiosis lipoidica diabeticorum) is a rare chronic granulomatous skin disease causing yellow-brown atrophic shin plaques, associated with diabetes, ulcerating in up to a third of cases, with no approved treatment.
Necrobiotic xanthogranuloma
Necrobiotic xanthogranuloma (NXG) is a rare, chronic non-Langerhans cell histiocytosis with yellow-orange, often periorbital plaques, strongly associated with paraproteinemia, MGUS, and multiple myeloma; first described 1980.
Necrosis
Necrosis, also called necrotic tissue or tissue necrosis, is the irreversible death of cells from injury, infection, or lost blood supply; widespread tissue death is called gangrene.
Necrotizing fasciitis
Necrotizing fasciitis, the flesh-eating disease, is a rapidly progressive bacterial infection destroying fascia and soft tissue, usually group A strep; treatment is urgent debridement plus penicillin and clindamycin, mortality 15–20%.
Neonatal acne
Neonatal acne (baby acne, neonatal cephalic pustulosis): a common self-limiting newborn rash affecting about 20% of newborns around 2 weeks of age, linked to Malassezia yeast, not true acne, clearing without scarring.
Neonatal antiphospholipid syndrome
Neonatal antiphospholipid syndrome, also known as Neonatal Hughes syndrome, is a rare autoimmune disorder in which newborns develop venous or arterial blood clots with antiphospholipid antibodies.
Neonatal compartment syndrome
Neonatal compartment syndrome (NCS, neonatal limb compartment syndrome) is a rare newborn condition of raised pressure in a limb compartment, usually the forearm, marked by a sentinel skin lesion; early fasciotomy gives the lowest sequelae rate.
Neonatal dermatomyositis
Neonatal dermatomyositis (Neonatal DM) is a rare autoimmune disorder of the newborn period causing widespread muscle weakness, severe hypotonia, diminished reflexes, and highly elevated creatine kinase.
Neonatal ichthyosis-sclerosing cholangitis syndrome
NISCH syndrome, also called ILVASC or IHSC, a very rare autosomal recessive CLDN1-related ichthyosis syndrome with neonatal ichthyosis, scalp hypotrichosis, scarring alopecia, and sclerosing cholangitis; 37 cases reported.
Neonatal lupus erythematosus
Neonatal lupus erythematosus, or neonatal lupus, is an autoimmune condition of fetuses and newborns caused by maternal anti-Ro antibodies crossing the placenta, causing rash and heart block.
Neonatal milia
Neonatal milia (milk spots) are benign keratin-filled white cysts present at birth in 40-50% of full-term newborns, mainly on the nose and face, resolving spontaneously within weeks without treatment; oral forms are Epstein pearls and Bohn nodules.
Neonatal miliaria
Neonatal miliaria, or heat rash, is a benign newborn rash from blocked eccrine sweat ducts; types include crystallina (clear 1–2 mm vesicles, up to 9% of neonates), rubra, and pustulosa; self-limiting with cooling.
Neonatal scleroderma
Neonatal scleroderma (ORPHA:398127) is a rare secondary neonatal autoimmune disease with linear erythematous lesions that become indurated, hyperpigmented, and atrophic; prevalence under 1 per million, ICD-10 P83.8.