237 articles
Severe primary trimethylaminuria
Severe primary trimethylaminuria (TMAU, fish odor syndrome, ORPHA:468726) is a rare autosomal recessive FMO3-deficiency disorder causing trimethylamine buildup and fishy body odor, with no cure but dietary and supportive treatment.
SHORT syndrome
SHORT syndrome is a rare autosomal dominant genetic disorder caused by PIK3R1 variants, first described in 1975, marked by short stature, distinctive facial features, teething delay, and insulin resistance.
Sialidosis type 1
Sialidosis type 1, or cherry-red spot myoclonus syndrome (mucolipidosis I), is a rare autosomal recessive lysosomal storage disease caused by NEU1 mutations, causing myoclonus, ataxia, visual loss, and macular cherry-red spots from adolescence.
Sialidosis type 2
Sialidosis type 2 (sialidosis type II, dysmorphic sialidosis, mucolipidosis I): severe early-onset autosomal recessive lysosomal storage disease from NEU1 neuraminidase deficiency, with congenital, infantile, and juvenile forms, coarse facies, cherry-red spots, and no approved disease-modifying therapy.
SLC39A8-CDG
SLC39A8-CDG (CDG-IIn, CDG2N, SLC39A8 deficiency) is a rare autosomal recessive congenital disorder of glycosylation caused by ZIP8 manganese-transporter variants, causing manganese depletion, type II transferrin profile, severe neurologic impairment, treatable with manganese and galactose.
Sodium-dependent multivitamin transporter deficiency
Sodium-dependent multivitamin transporter deficiency, also called SMVT deficiency or SLC5A6 deficiency (OMIM 618973), is an ultra-rare autosomal recessive metabolic disorder impairing intestinal uptake of biotin, pantothenic acid, and lipoate, treatable with high-dose vitamins.
Squalene synthase deficiency
Squalene synthase deficiency (SQSD, OMIM 618156) is a rare autosomal recessive cholesterol biosynthesis disorder caused by biallelic FDFT1 variants, marked by neonatal seizures, profound developmental delay, and farnesol-derived urine metabolites.
Succinic semialdehyde dehydrogenase deficiency
Succinic semialdehyde dehydrogenase deficiency (SSADHD, 4-hydroxybutyric aciduria, gamma-hydroxybutyric aciduria), ALDH5A1 autosomal recessive GABA metabolism disorder causing intellectual disability, hypotonia, ataxia, epilepsy; prevalence about 1/500,000.
Syndrome
Syndrome: a group of signs and symptoms occurring together and characterizing an abnormality, from Greek syndromē 'running together'. Distinguished from disease (known cause) and disorder; examples include Down and metabolic syndrome.
Tangier disease
Tangier disease is a rare autosomal recessive cholesterol transport disorder with almost no HDL, causing orange-yellow tonsils, enlarged liver and spleen, and peripheral neuropathy, named for Tangier Island, Virginia.
Terminal illness
A terminal illness, also called a terminal or end-stage disease, is a disease that cannot be cured or controlled with treatment and is expected to lead to death.
Thiamine-responsive megaloblastic anemia syndrome
Thiamine-responsive megaloblastic anemia syndrome (TRMA, Rogers syndrome): rare autosomal recessive SLC19A2 disorder causing megaloblastic anemia, diabetes, and sensorineural deafness, treatable with high-dose thiamine.
Transient hyperammonemia of the newborn
Transient hyperammonemia of the newborn (THAN, ORPHA:289877) is a temporary, non-inherited neonatal hyperammonemia, mainly in preterm infants, diagnosed by exclusion, treated with scavengers and CRRT, with good prognosis.
Transient tyrosinemia of the newborn
Transient tyrosinemia of the newborn (transient neonatal tyrosinemia, ICD-10 P74.5) is a benign, self-limiting elevation of blood tyrosine in newborns, especially preterm infants on high-protein diets, caused by immature liver 4-HPPD enzyme and usually resolving by 2 months.
Transketolase deficiency
Transketolase deficiency (TKT deficiency) is a rare autosomal recessive pentose phosphate pathway disorder caused by TKT variants on 3p21.1, causing short stature, developmental delay, congenital heart defects, and elevated polyols.
Triose phosphate-isomerase deficiency
Triosephosphate isomerase deficiency (TPI deficiency, TPID) is an ultra-rare autosomal recessive glycolytic enzymopathy caused by TPI1 mutations, mostly E105D, causing hemolytic anemia, progressive neuromuscular degeneration, and childhood death.
Tumor lysis syndrome
Tumor lysis syndrome (TLS), an oncometabolic emergency from rapid cancer cell death causing hyperuricemia, hyperkalemia, hyperphosphatemia, and hypocalcemia; defined by Cairo-Bishop criteria, risk-stratified, prevented with hydration, allopurinol, and rasburicase.
Tyrosinemia type 1
Tyrosinemia type 1 (HT-1, hepatorenal tyrosinemia) is an autosomal recessive FAH-deficiency disorder causing liver and kidney damage, neurologic crises, and HCC risk; treated with nitisinone and a low-tyrosine diet.
Tyrosinemia type 2
Tyrosinemia type 2 (Richner-Hanhart syndrome, oculocutaneous tyrosinemia) is a rare autosomal recessive disorder caused by TAT gene deficiency at 16q22.2, causing corneal dystrophy, painful palmoplantar hyperkeratosis, and intellectual disability in about half of cases, treated with a tyrosine- and phenylalanine-restricted diet.
Tyrosinemia type 3
Tyrosinemia type 3 is a rare inherited disorder of tyrosine metabolism caused by HPD enzyme deficiency, marked by high blood tyrosine and, in some cases, intellectual disability and seizures.
Urocanic aciduria
Urocanic aciduria (urocanase deficiency, encephalopathy due to urocanase deficiency, OMIM 276880) is an extremely rare autosomal recessive histidine metabolism disorder caused by UROC1 deficiency, causing urinary urocanic acid with variable ataxia and intellectual deficit, often benign.
Variegate porphyria
Variegate porphyria (porphyria variegata), a rare autosomal dominant heme biosynthesis disorder from PPOX mutations, causes both blistering photosensitivity and acute neurovisceral attacks; highly prevalent in South Africa via the R59W founder mutation.
Very long chain acyl-CoA dehydrogenase deficiency
VLCAD deficiency, also called very long-chain acyl-CoA dehydrogenase deficiency, is an autosomal recessive ACADVL disorder impairing beta-oxidation of 14-20 carbon fatty acids, causing hypoketotic hypoglycemia, cardiomyopathy, and rhabdomyolysis, detected by C14:1 newborn screening.
Vitamin B12-responsive methylmalonic acidemia
Vitamin B12-responsive methylmalonic acidemia is an inherited metabolic disorder in which methylmalonic acid builds up because of defective vitamin B12 metabolism, causing ketoacidotic comas in infancy that improve with vitamin B12 treatment.
Vitamin B12-unresponsive methylmalonic acidemia
Vitamin B12-unresponsive methylmalonic acidemia (mut0, mut-) is an autosomal recessive MUT-gene disorder of methylmalonyl-CoA mutase causing neonatal ketoacidosis, hyperammonemia, renal failure, and metabolic stroke that cobalamin therapy does not improve.
Wolfram syndrome
Wolfram syndrome (DIDMOAD), rare autosomal recessive neurodegenerative disorder from WFS1 or CISD2 mutations: juvenile diabetes, optic atrophy, deafness, diabetes insipidus; median death age about 30.
X-linked erythropoietic protoporphyria
X-linked erythropoietic protoporphyria (XLP, XLDPP, OMIM 300752), an X-linked dominant protoporphyria from ALAS2 gain-of-function variants causing protoporphyrin IX accumulation and painful childhood photosensitivity; metal-free PPIX 50-85%, FECH normal.