MedGen

Cystic fibrosis (CF) is a multisystem disease affecting epithelia of the respiratory tract, exocrine pancreas, intestine, hepatobiliary system, and exocrine sweat glands. Morbidities include recurrent sinusitis and bronchitis, progressive obstructive pulmonary disease with bronchiectasis, exocrine pancreatic deficiency and malnutrition, pancreatitis, gastrointestinal manifestations (meconium ileus, rectal prolapse, distal intestinal obstructive syndrome), liver disease, diabetes, male infertility due to hypoplasia or aplasia of the vas deferens, and reduced fertility or infertility in some women. Pulmonary disease is the major cause of morbidity and mortality in CF. [from GeneReviews]

The spectrum of propionic acidemia (PA) ranges from neonatal onset to late-onset disease. Neonatal-onset PA, the most common form, is characterized by a healthy newborn with poor feeding and decreased arousal in the first few days of life, followed by progressive encephalopathy of unexplained origin. Without prompt diagnosis (often through newborn screening) and management, this is followed by progressive encephalopathy manifesting as lethargy, seizures, or coma that can result in death. It is frequently accompanied by metabolic acidosis with anion gap, lactic acidosis, ketonuria, hypoglycemia, hyperammonemia, and cytopenias. Individuals with late-onset PA may remain asymptomatic and suffer a metabolic crisis under catabolic stress (e.g., illness, surgery, fasting) or may experience a more insidious onset with the development of multiorgan complications including vomiting, protein intolerance, failure to thrive, hypotonia, developmental delays or regression, movement disorders, or cardiomyopathy. Isolated cardiomyopathy can be observed on rare occasions in the absence of clinical metabolic decompensation or neurocognitive deficits. Manifestations of neonatal-onset and late-onset PA over time can include growth impairment, intellectual disability, seizures, basal ganglia lesions, pancreatitis, cardiomyopathy, and chronic kidney disease. Other rarely reported complications include optic atrophy, sensorineural hearing loss, and premature ovarian insufficiency. [from GeneReviews]

Primary carnitine deficiency (PCD) is a disorder of the carnitine cycle that results in defective fatty acid oxidation. If untreated, it encompasses a broad clinical spectrum including: (1) metabolic decompensation in infancy typically presenting between age three months and two years with episodes of hypoketotic hypoglycemia, poor feeding, irritability, lethargy, hepatomegaly, elevated liver transaminases, and hyperammonemia triggered by fasting or common illnesses such as upper respiratory tract infection or gastroenteritis; (2) childhood myopathy involving heart and skeletal muscle with onset between age two and four years; (3) pregnancy-related decreased stamina or exacerbation of cardiac arrhythmia; (4) fatigability in adulthood; and (5) absence of symptoms. The latter two categories often include mothers diagnosed with PCD after newborn screening has identified low carnitine levels in their infants. [from GeneReviews]

Cystinosis comprises three allelic phenotypes: Nephropathic cystinosis in untreated children is characterized by renal Fanconi syndrome, poor growth, hypophosphatemic/calcipenic rickets, impaired glomerular function resulting in complete glomerular failure, and accumulation of cystine in almost all cells, leading to cellular dysfunction with tissue and organ impairment. The typical untreated child has short stature, rickets, and photophobia. Failure to thrive is generally noticed after approximately age six months; signs of renal tubular Fanconi syndrome (polyuria, polydipsia, dehydration, and acidosis) appear as early as age six months; corneal crystals can be present before age one year and are always present after age 16 months. Prior to the use of renal transplantation and cystine-depleting therapy, the life span in nephropathic cystinosis was no longer than ten years. With these interventions, affected individuals can survive at least into the mid-forties or fifties with satisfactory quality of life. Intermediate cystinosis is characterized by all the typical manifestations of nephropathic cystinosis, but onset is at a later age. Renal glomerular failure occurs in all untreated affected individuals, usually between ages 15 and 25 years. The non-nephropathic (ocular) form of cystinosis is characterized clinically only by photophobia resulting from corneal cystine crystal accumulation. [from GeneReviews]

3-Hydroxy-3-methylglutaryl-CoA lyase deficiency (HMGCLD) is a rare autosomal recessive disorder with the cardinal manifestations of metabolic acidosis without ketonuria, hypoglycemia, and a characteristic pattern of elevated urinary organic acid metabolites, including 3-hydroxy-3-methylglutaric, 3-methylglutaric, and 3-hydroxyisovaleric acids. Urinary levels of 3-methylcrotonylglycine may be increased. Dicarboxylic aciduria, hepatomegaly, and hyperammonemia may also be observed. Presenting clinical signs include irritability, lethargy, coma, and vomiting (summary by Gibson et al., 1988). [from OMIM]

Primary hyperoxaluria type 1 (PH1) is caused by deficiency of the liver peroxisomal enzyme alanine-glyoxylate aminotransferase (AGT), which catalyzes the conversion of glyoxylate to glycine. When AGT activity is reduced or absent, glyoxylate is converted to oxalate, which cannot be metabolized and must be excreted by the kidneys. Insoluble calcium oxalate crystals form due to high urinary oxalate concentration. Urinary crystals aggregate, leading to nephrolithiasis (i.e., calcium oxalate kidney stones) in the renal pelvis / urinary tract; often the crystals deposit in kidney parenchyma (nephrocalcinosis). The age at presentation of PH1 ranges from infancy (age <12 months) in 10% of individuals, childhood/adolescence (age 1-17 years) in 70%, and adulthood (age =18 years) in 20%. The natural history of untreated PH1 is (1) progressive decline in kidney function due to complications of nephrolithiasis (e.g., urinary obstruction, infection) and nephrocalcinosis, and (2) in persons with advanced chronic kidney disease (CKD), high plasma oxalate concentrations result in other organ and tissue damage from calcium oxalate deposition (i.e., "oxalosis"), most commonly in the bones, heart, and retina. In the absence of treatment, progression of oxalosis results in death from kidney failure and/or other organ involvement. [from GeneReviews]

Individuals with clinical manifestations of isovaleric acidemia (IVA) have either classic IVA identified on newborn screening or classic IVA with a later diagnosis due to a missed diagnosis or later onset of clinical manifestations. Classic IVA is characterized by acute metabolic decompensations (vomiting, poor feeding, lethargy, hypotonia, seizures, and a distinct odor of sweaty feet). Acute metabolic decompensations are typically triggered by fasting, (febrile) illness (especially gastroenteritis), or increased protein intake. Clinical deterioration often occurs within hours to days after birth. Additional manifestations of classic IVA include developmental delay, intellectual disability and/or impaired cognition, epilepsy, and movement disorder (tremor, dysmetria, extrapyramidal movements). Early treatment in those identified by newborn screening can significantly reduce morbidity and mortality in individuals with classic IVA. [from GeneReviews]

For this GeneReview, the term "isolated methylmalonic acidemia" refers to a group of inborn errors of metabolism associated with elevated methylmalonic acid (MMA) concentration in the blood and urine that result from the failure to isomerize (convert) methylmalonyl-coenzyme A (CoA) into succinyl-CoA during propionyl-CoA metabolism in the mitochondrial matrix, without hyperhomocysteinemia or homocystinuria, hypomethioninemia, or variations in other metabolites, such as malonic acid. Isolated MMA is caused by complete or partial deficiency of the enzyme methylmalonyl-CoA mutase (mut0 enzymatic subtype or mut– enzymatic subtype, respectively), a defect in the transport or synthesis of its cofactor, 5-deoxy-adenosyl-cobalamin (cblA, cblB, or cblD-MMA), or deficiency of the enzyme methylmalonyl-CoA epimerase. Prior to the advent of newborn screening, common phenotypes included: Infantile/non-B12-responsive form (mut0 enzymatic subtype, cblB), the most common phenotype, associated with infantile-onset lethargy, tachypnea, hypothermia, vomiting, and dehydration on initiation of protein-containing feeds. Without appropriate treatment, the infantile/non-B12-responsive phenotype could rapidly progress to coma due to hyperammonemic encephalopathy. Partially deficient or B12-responsive phenotypes (mut– enzymatic subtype, cblA, cblB [rare], cblD-MMA), in which symptoms occur in the first few months or years of life and are characterized by feeding problems, failure to thrive, hypotonia, and developmental delay marked by episodes of metabolic decompensation. Methylmalonyl-CoA epimerase deficiency, in which findings range from complete absence of symptoms to severe metabolic acidosis. Affected individuals can also develop ataxia, dysarthria, hypotonia, mild spastic paraparesis, and seizures. In those individuals diagnosed by newborn screening and treated from an early age, there appears to be decreased early mortality, less severe symptoms at diagnosis, favorable short-term neurodevelopmental outcome, and lower incidence of movement disorders and irreversible cerebral damage. However, secondary complications may still occur and can include intellectual disability, tubulointerstitial nephritis with progressive impairment of renal function, "metabolic stroke" (bilateral lacunar infarction of the basal ganglia during acute metabolic decompensation), pancreatitis, growth failure, functional immune impairment, bone marrow failure, optic nerve atrophy, arrhythmias and/or cardiomyopathy (dilated or hypertrophic), liver steatosis/fibrosis/cancer, and renal cancer. [from GeneReviews]

Alpha-methylacetoacetic aciduria, also known as 3-ketothiolase deficiency, is an inborn error of isoleucine catabolism characterized by urinary excretion of 2-methyl-3-hydroxybutyric acid, 2-methylacetoacetic acid, tiglylglycine, and 2-butanone. [from OMIM]

For this GeneReview, the term "isolated methylmalonic acidemia" refers to a group of inborn errors of metabolism associated with elevated methylmalonic acid (MMA) concentration in the blood and urine that result from the failure to isomerize (convert) methylmalonyl-coenzyme A (CoA) into succinyl-CoA during propionyl-CoA metabolism in the mitochondrial matrix, without hyperhomocysteinemia or homocystinuria, hypomethioninemia, or variations in other metabolites, such as malonic acid. Isolated MMA is caused by complete or partial deficiency of the enzyme methylmalonyl-CoA mutase (mut0 enzymatic subtype or mut– enzymatic subtype, respectively), a defect in the transport or synthesis of its cofactor, 5-deoxy-adenosyl-cobalamin (cblA, cblB, or cblD-MMA), or deficiency of the enzyme methylmalonyl-CoA epimerase. Prior to the advent of newborn screening, common phenotypes included: Infantile/non-B12-responsive form (mut0 enzymatic subtype, cblB), the most common phenotype, associated with infantile-onset lethargy, tachypnea, hypothermia, vomiting, and dehydration on initiation of protein-containing feeds. Without appropriate treatment, the infantile/non-B12-responsive phenotype could rapidly progress to coma due to hyperammonemic encephalopathy. Partially deficient or B12-responsive phenotypes (mut– enzymatic subtype, cblA, cblB [rare], cblD-MMA), in which symptoms occur in the first few months or years of life and are characterized by feeding problems, failure to thrive, hypotonia, and developmental delay marked by episodes of metabolic decompensation. Methylmalonyl-CoA epimerase deficiency, in which findings range from complete absence of symptoms to severe metabolic acidosis. Affected individuals can also develop ataxia, dysarthria, hypotonia, mild spastic paraparesis, and seizures. In those individuals diagnosed by newborn screening and treated from an early age, there appears to be decreased early mortality, less severe symptoms at diagnosis, favorable short-term neurodevelopmental outcome, and lower incidence of movement disorders and irreversible cerebral damage. However, secondary complications may still occur and can include intellectual disability, tubulointerstitial nephritis with progressive impairment of renal function, "metabolic stroke" (bilateral lacunar infarction of the basal ganglia during acute metabolic decompensation), pancreatitis, growth failure, functional immune impairment, bone marrow failure, optic nerve atrophy, arrhythmias and/or cardiomyopathy (dilated or hypertrophic), liver steatosis/fibrosis/cancer, and renal cancer. [from GeneReviews]

NR0B1-related adrenal hypoplasia congenita includes both X-linked adrenal hypoplasia congenita (X-linked AHC) and Xp21 deletion (previously called complex glycerol kinase deficiency). X-linked AHC is characterized by primary adrenal insufficiency and/or hypogonadotropic hypogonadism (HH). Adrenal insufficiency is acute infantile onset (average age 3 weeks) in approximately 60% of affected males and childhood onset (ages 1-9 years) in approximately 40%. HH typically manifests in a male with adrenal insufficiency as delayed puberty (i.e., onset age >14 years) and less commonly as arrested puberty at about Tanner Stage 3. Rarely, X-linked AHC manifests initially in early adulthood as delayed-onset adrenal insufficiency, partial HH, and/or infertility. Heterozygous females very occasionally have manifestations of adrenal insufficiency or hypogonadotropic hypogonadism. Xp21 deletion includes deletion of NR0B1 (causing X-linked AHC) and GK (causing glycerol kinase deficiency), and in some cases deletion of DMD (causing Duchenne muscular dystrophy). Developmental delay has been reported in males with Xp21 deletion when the deletion extends proximally to include DMD or when larger deletions extend distally to include IL1RAPL1 and DMD. [from GeneReviews]

For this GeneReview, the term "isolated methylmalonic acidemia" refers to a group of inborn errors of metabolism associated with elevated methylmalonic acid (MMA) concentration in the blood and urine that result from the failure to isomerize (convert) methylmalonyl-coenzyme A (CoA) into succinyl-CoA during propionyl-CoA metabolism in the mitochondrial matrix, without hyperhomocysteinemia or homocystinuria, hypomethioninemia, or variations in other metabolites, such as malonic acid. Isolated MMA is caused by complete or partial deficiency of the enzyme methylmalonyl-CoA mutase (mut0 enzymatic subtype or mut– enzymatic subtype, respectively), a defect in the transport or synthesis of its cofactor, 5-deoxy-adenosyl-cobalamin (cblA, cblB, or cblD-MMA), or deficiency of the enzyme methylmalonyl-CoA epimerase. Prior to the advent of newborn screening, common phenotypes included: Infantile/non-B12-responsive form (mut0 enzymatic subtype, cblB), the most common phenotype, associated with infantile-onset lethargy, tachypnea, hypothermia, vomiting, and dehydration on initiation of protein-containing feeds. Without appropriate treatment, the infantile/non-B12-responsive phenotype could rapidly progress to coma due to hyperammonemic encephalopathy. Partially deficient or B12-responsive phenotypes (mut– enzymatic subtype, cblA, cblB [rare], cblD-MMA), in which symptoms occur in the first few months or years of life and are characterized by feeding problems, failure to thrive, hypotonia, and developmental delay marked by episodes of metabolic decompensation. Methylmalonyl-CoA epimerase deficiency, in which findings range from complete absence of symptoms to severe metabolic acidosis. Affected individuals can also develop ataxia, dysarthria, hypotonia, mild spastic paraparesis, and seizures. In those individuals diagnosed by newborn screening and treated from an early age, there appears to be decreased early mortality, less severe symptoms at diagnosis, favorable short-term neurodevelopmental outcome, and lower incidence of movement disorders and irreversible cerebral damage. However, secondary complications may still occur and can include intellectual disability, tubulointerstitial nephritis with progressive impairment of renal function, "metabolic stroke" (bilateral lacunar infarction of the basal ganglia during acute metabolic decompensation), pancreatitis, growth failure, functional immune impairment, bone marrow failure, optic nerve atrophy, arrhythmias and/or cardiomyopathy (dilated or hypertrophic), liver steatosis/fibrosis/cancer, and renal cancer. [from GeneReviews]

MPV17-related mitochondrial DNA (mtDNA) maintenance defect presents in the vast majority of affected individuals as an early-onset encephalohepatopathic (hepatocerebral) disease that is typically associated with mtDNA depletion, particularly in the liver. A later-onset neuromyopathic disease characterized by myopathy and neuropathy, and associated with multiple mtDNA deletions in muscle, has also rarely been described. MPV17-related mtDNA maintenance defect, encephalohepatopathic form is characterized by: Hepatic manifestations (liver dysfunction that typically progresses to liver failure, cholestasis, hepatomegaly, and steatosis); Neurologic involvement (developmental delay, hypotonia, microcephaly, and motor and sensory peripheral neuropathy); Gastrointestinal manifestations (gastrointestinal dysmotility, feeding difficulties, and failure to thrive); and Metabolic derangements (lactic acidosis and hypoglycemia). Less frequent manifestations include renal tubulopathy, nephrocalcinosis, and hypoparathyroidism. Progressive liver disease often leads to death in infancy or early childhood. Hepatocellular carcinoma has been reported. [from GeneReviews]

Bartter syndrome refers to a group of disorders that are unified by autosomal recessive transmission of impaired salt reabsorption in the thick ascending loop of Henle with pronounced salt wasting, hypokalemic metabolic alkalosis, and hypercalciuria. Clinical disease results from defective renal reabsorption of sodium chloride in the thick ascending limb (TAL) of the Henle loop, where 30% of filtered salt is normally reabsorbed (Simon et al., 1997). Patients with antenatal (or neonatal) forms of Bartter syndrome (e.g., BARTS1, 601678) typically present with premature birth associated with polyhydramnios and low birth weight and may develop life-threatening dehydration in the neonatal period. Patients with classic Bartter syndrome present later in life and may be sporadically asymptomatic or mildly symptomatic (summary by Simon et al., 1996 and Fremont and Chan, 2012). Genetic Heterogeneity of Bartter Syndrome Antenatal Bartter syndrome type 1 (601678) is caused by loss-of-function mutations in the butmetanide-sensitive Na-K-2Cl cotransporter NKCC2 (SLC12A1; 600839). Antenatal Bartter syndrome type 2 (241200) is caused by loss-of-function mutations in the ATP-sensitive potassium channel ROMK (KCNJ1; 600359). One form of neonatal Bartter syndrome with sensorineural deafness, Bartter syndrome type 4A (602522), is caused by mutation in the BSND gene (606412). Another form of neonatal Bartter syndrome with sensorineural deafness, Bartter syndrome type 4B (613090), is caused by simultaneous mutation in both the CLCNKA (602024) and CLCNKB (602023) genes. Also see autosomal dominant hypocalcemia-1 with Bartter syndrome (601198), which is sometimes referred to as Bartter syndrome type 5 (Fremont and Chan, 2012), caused by mutation in the CASR gene (601199). See Gitelman syndrome (GTLMN; 263800), which is often referred to as a mild variant of Bartter syndrome, caused by mutation in the thiazide-sensitive sodium-chloride cotransporter SLC12A3 (600968). [from OMIM]

Combined malonic and methylmalonic aciduria (CMAMMA) is a rare recessive inborn error of metabolism characterized by elevations of urine malonic acid (MA) and methylmalonic acid (MMA). MMA excretion is higher than MA in CMAMMA patients, unlike patients with malonyl-CoA decarboxylase deficiency (248360) in whom the biochemical abnormalities include elevated MA alone or combined elevations of MA and MMA with MA mainly being higher than MMA. The clinical significance of CMAMMA is controversial. Initially, CMAMMA patients were ascertained during investigation of children with symptoms suggestive of a metabolic disorder or adults with neurologic manifestations (Sloan et al., 2011). Levtova et al. (2019) described CMAMMA patients identified by neonatal screening who had a favorable clinical course. [from OMIM]

Bartter syndrome refers to a group of disorders that are unified by autosomal recessive transmission of impaired salt reabsorption in the thick ascending loop of Henle with pronounced salt wasting, hypokalemic metabolic alkalosis, and hypercalciuria. Clinical disease results from defective renal reabsorption of sodium chloride in the thick ascending limb (TAL) of the Henle loop, where 30% of filtered salt is normally reabsorbed (Simon et al., 1997). Patients with antenatal forms of Bartter syndrome typically present with premature birth associated with polyhydramnios and low birth weight and may develop life-threatening dehydration in the neonatal period. Patients with classic Bartter syndrome (see BARTS3, 607364) present later in life and may be sporadically asymptomatic or mildly symptomatic (summary by Simon et al., 1996 and Fremont and Chan, 2012). For a discussion of genetic heterogeneity of Bartter syndrome, see 607364. [from OMIM]

Bartter syndrome refers to a group of disorders that are unified by autosomal recessive transmission of impaired salt reabsorption in the thick ascending loop of Henle with pronounced salt wasting, hypokalemic metabolic alkalosis, and hypercalciuria. Clinical disease results from defective renal reabsorption of sodium chloride in the thick ascending limb (TAL) of the Henle loop, where 30% of filtered salt is normally reabsorbed (Simon et al., 1997). Patients with antenatal forms of Bartter syndrome typically present with premature birth associated with polyhydramnios and low birth weight and may develop life-threatening dehydration in the neonatal period. Patients with classic Bartter syndrome (see BARTS3, 607364) present later in life and may be sporadically asymptomatic or mildly symptomatic (summary by Simon et al., 1996 and Fremont and Chan, 2012). For a discussion of genetic heterogeneity of Bartter syndrome, see 607364. [from OMIM]

For this GeneReview, the term "isolated methylmalonic acidemia" refers to a group of inborn errors of metabolism associated with elevated methylmalonic acid (MMA) concentration in the blood and urine that result from the failure to isomerize (convert) methylmalonyl-coenzyme A (CoA) into succinyl-CoA during propionyl-CoA metabolism in the mitochondrial matrix, without hyperhomocysteinemia or homocystinuria, hypomethioninemia, or variations in other metabolites, such as malonic acid. Isolated MMA is caused by complete or partial deficiency of the enzyme methylmalonyl-CoA mutase (mut0 enzymatic subtype or mut– enzymatic subtype, respectively), a defect in the transport or synthesis of its cofactor, 5-deoxy-adenosyl-cobalamin (cblA, cblB, or cblD-MMA), or deficiency of the enzyme methylmalonyl-CoA epimerase. Prior to the advent of newborn screening, common phenotypes included: Infantile/non-B12-responsive form (mut0 enzymatic subtype, cblB), the most common phenotype, associated with infantile-onset lethargy, tachypnea, hypothermia, vomiting, and dehydration on initiation of protein-containing feeds. Without appropriate treatment, the infantile/non-B12-responsive phenotype could rapidly progress to coma due to hyperammonemic encephalopathy. Partially deficient or B12-responsive phenotypes (mut– enzymatic subtype, cblA, cblB [rare], cblD-MMA), in which symptoms occur in the first few months or years of life and are characterized by feeding problems, failure to thrive, hypotonia, and developmental delay marked by episodes of metabolic decompensation. Methylmalonyl-CoA epimerase deficiency, in which findings range from complete absence of symptoms to severe metabolic acidosis. Affected individuals can also develop ataxia, dysarthria, hypotonia, mild spastic paraparesis, and seizures. In those individuals diagnosed by newborn screening and treated from an early age, there appears to be decreased early mortality, less severe symptoms at diagnosis, favorable short-term neurodevelopmental outcome, and lower incidence of movement disorders and irreversible cerebral damage. However, secondary complications may still occur and can include intellectual disability, tubulointerstitial nephritis with progressive impairment of renal function, "metabolic stroke" (bilateral lacunar infarction of the basal ganglia during acute metabolic decompensation), pancreatitis, growth failure, functional immune impairment, bone marrow failure, optic nerve atrophy, arrhythmias and/or cardiomyopathy (dilated or hypertrophic), liver steatosis/fibrosis/cancer, and renal cancer. [from GeneReviews]

Autosomal recessive pseudohypoaldosteronism type I, including PHA1B1, is characterized by renal salt wasting and high concentrations of sodium in sweat, stool, and saliva. The disorder involves multiple organ systems and is especially threatening in the neonatal period. Laboratory evaluation shows hyponatremia, hyperkalemia, and increased plasma renin activity with high serum aldosterone concentrations. Respiratory tract infections are common in affected children and may be mistaken for cystic fibrosis (CF; 219700). Aggressive salt replacement and control of hyperkalemia results in survival, and the disorder appears to become less severe with age (review by Scheinman et al., 1999). A milder, autosomal dominant form of type I pseudohypoaldosteronism (PHA1A; 177735) is caused by mutations in the mineralocorticoid receptor gene (MCR, NR3C2; 600983). Gitelman syndrome (263800), another example of primary renal tubular salt wasting, is due to mutation in the thiazide-sensitive sodium-chloride cotransporter (SLC12A3; 600968). Hanukoglu and Hanukoglu (2016) provided a detailed review of the ENaC gene family, including structure, function, tissue distribution, and associated inherited diseases. [from OMIM]

6q24-related transient neonatal diabetes mellitus (6q24-TNDM) is defined as transient neonatal diabetes mellitus caused by genetic aberrations of the imprinted locus at 6q24. The cardinal features are: severe intrauterine growth restriction, hyperglycemia that begins in the neonatal period in a term infant and resolves by age 18 months, dehydration, and absence of ketoacidosis. Macroglossia and umbilical hernia may be present. 6q24-TNDM associated with a multilocus imprinting disturbance (MLID) can be associated with marked hypotonia, congenital heart disease, deafness, neurologic features including epilepsy, and renal malformations. Diabetes mellitus usually starts within the first week of life and lasts on average three months but can last longer than a year. Although insulin is usually required initially, the need for insulin gradually declines over time. Intermittent episodes of hyperglycemia may occur in childhood, particularly during intercurrent illnesses. Diabetes mellitus may recur in adolescence or later in adulthood. Women who have had 6q24-TNDM are at risk for relapse during pregnancy. [from GeneReviews]