Clinical manifestations

Presentation and course

Acute clinical manifestations

Long-term or chronic clinical manifestations

As over 300 mutations or polymorphisms in the GALT gene have been identified, different forms of the deficiency exist (39; 137; 24).

Classic galactosemia

Infants with complete or near-complete deficiency of the enzyme (classic galactosemia) have normal weight at birth but, as they start ingesting lactose-containing breast milk or formula, lose more weight than their healthy peers and fail to regain birth weight (122; 08; 47; 17). Almost all infants on a lactose-containing diet manifest poor weight gain. Symptoms appear in the second half of the first week and include refusal to feed, vomiting, jaundice, and lethargy. Parents often report various feeding difficulties with their newborn, most notably, vomiting. Hepatomegaly, edema, and ascites may follow. Ascites may be detected in early infancy. In some patients, ascites is detected as early as the first few days of life. Death from sepsis, usually due to E coli, may occur in most infants with classic disease who have not been detected by newborn screening. Symptoms are milder and the course is less precipitous when milk is temporarily withdrawn and replaced by intravenous nutrition. Nuclear cataracts appear within days or weeks and become irreversible within weeks of their appearance. Congenital cataracts and vitreous hemorrhages may also be present (83; 130). In an infant or child with cataracts, galactosemia must be excluded. An ophthalmologist needs to be consulted because some cataracts, especially congenital cataracts, are visible only with a slit lamp. Vitreous hemorrhage is a known complication of galactosemia, although its prevalence is unknown (83; 130).

In many countries, newborns with galactosemia are discovered through newborn screening by quantifying blood galactose, the GALT enzyme, or both; this screening is performed using dried blood spots, usually collected on the second day of life in the United States (10; 107; 108). At the time of discovery, the first symptoms may already have appeared, and the infant may already have been admitted to a hospital, usually for jaundice. Where newborns are not screened for galactosemia or when the results of screening are not yet available, diagnosis rests on clinical awareness. It is crucial that milk feeding be stopped as soon as galactosemia is considered and resumed only when a galactose disorder has been excluded. The presence of a reducing substance in a routine urine specimen may be the first diagnostic clue. Galactosuria will be present provided that last milk feed does not date back more than a few hours and vomiting has not been excessive. However, owing to the early development of a proximal renal tubular syndrome, the acutely ill galactosemic infant may also excrete some glucose, together with an excess of amino acids. However, glucosuria may be recognized, and the galactosuria missed. On withholding milk, galactosuria ceases, but amino acids in excess continue to be excreted for a few days. However, galactitol and galactonate continue to be excreted in large amounts. Albuminuria may also be an early finding that disappears with dietary lactose restriction.

As an autosomal recessive disorder, galactosemia equally affects males and females.

Clinical variant galactosemia

Over 300 known pathogenic GALT variants are detectable by sequencing. Clinical variant galactosemia, as exemplified by the disease that occurs in African Americans and native Africans in South Africa (123; 125; 03; 124; 111; 122; 10) can result in life-threatening complications in untreated infants, including feeding problems, failure to thrive, hepatocellular damage including cirrhosis, and bleeding. Affected individuals may have approximately 10% of enzyme activity in liver and intestinal epithelium but no activity in erythrocytes.

The S135L mutation in the GALT gene is a prevalent cause of galactosemia among black patients, accounting for almost half of the GALT alleles in galactosemia patients of African-American descent (77; 78; 152; 92; 08; 58). African Americans with clinical variant galactosemia who receive adequate early treatment are apparently not at risk for long-term complications. If a lactose-restricted diet is provided during the first 10 days of life, the severe acute neonatal complications are usually prevented. Unfortunately, the ability of an individual with the variant gene defect to tolerate ingestion of some milk may hinder diagnosis in locales without newborn screening. Even in areas with newborn screening, the clinical variant form of galactosemia due to homozygosity for the S135L GALT gene mutation can be missed when newborn screening depends on an elevated total galactose level (35; 10).

Benign variant galactosemia (Duarte variant galactosemia)

Benign variant galactosemia, the most common of which is Duarte variant galactosemia, is associated with partial deficiency in erythrocyte GALT enzyme activity but is typically not associated with clinical disease (28; 44). It is most often discovered by newborn screening because of moderately elevated blood galactose (free or total) or low GALT activity. Dietary therapy is often not recommended (and likely not necessary) (27).

During infancy, but less so in childhood, these individuals may have elevated galactose metabolite levels (40). Whether dietary galactose restriction is necessary or beneficial for patients with Duarte variant galactosemia was long unknown and a matter of intense debate (106; 02; 44; 91). An important study by Carlock and colleagues directly assessed speech–language outcomes in 350 children (250 with Duarte galactosemia and 144 controls) (27; 43). Duarte galactosemia was not associated with adverse developmental outcomes in children aged 6 to 12 years compared to children without Duarte galactosemia. Milk exposure during infancy was not associated with adverse developmental outcomes in children with Duarte galactosemia.

Prognosis and complications

Most patients with classic galactosemia who are detected via newborn screening between 4 to 7 days and placed on a lactose-restricted diet will not develop severe multiorgan disease and E coli sepsis. However, if these steps are not taken, affected infants are likely to die of E coli sepsis or go on to develop cirrhosis and/or severe white matter lesions (100). Even patients treated on day 1 of life may manifest CNS disease associated with language delay, speech defects, cognitive impairment, learning problems, and, less commonly, tremors, ataxia, and dystonia, plus, at least in females, hypergonadotropic hypogonadism or primary ovarian insufficiency. Therefore, all patients with classic disease require multiple evaluations at different points in time and appropriate treatment. Complications that can vary in severity for each individual independent of erythrocyte galactose-1-phosphate and urine galactitol levels collected over many years on diet therapy. The variation in developmental, cognitive, and neurologic complications may be striking for one individual compared to another, but this is less so for primary ovarian insufficiency in females, as almost all show biochemical evidence of hypergonadotropic hypogonadism.

Clinical vignette

On day 6 of life, a male infant was lethargic, feeding poorly, and had temperature instability. A workup for sepsis was negative. On day 8, urine-reducing substances were 4+, and results of newborn screening on a sample obtained on day 2 were positive for galactosemia with a total blood galactose plus galactose-1-phosphate level higher than 9 mg/dL (normal, less than 7.2). Galactose-restricted feeding was initiated with Isomil (Ross Laboratories, Columbus, Ohio). Because his condition continued to deteriorate, he was transferred to the neonatal intensive care unit on day 10. On physical examination, the infant was quiet but arousable. Skin perfusion was poor. Spontaneous deep hyperventilation was occasionally noted. Jaundice and hepatomegaly were present. Major laboratory abnormalities consisted of hyperchloremic metabolic acidosis, mild hypertransaminasemia, hypofibrinogenemia, prolonged prothrombin and partial thromboplastin times, hyperbilirubinemia, and thrombocytopenia. The erythrocyte galactose-1-phosphate level was 33.9 mg/dL (normal, less than 1 mg/dL). The plasma galactitol concentration was 407 μmol/L (normal, less than 1 μmol/L), and urinary galactitol excretion was 4754 μmol/mmol creatinine (normal, 2 to 78 μmol/mmol creatinine for infants younger than 1 year old). Erythrocyte GALT activity was absent, and the patient was homozygous for Q188R, the most common severe GALT mutation. Brain magnetic resonance imaging and 1H-MRS studies were performed with a Siemens Magnetom Vision 1.5 T whole-body MRI scanner. Brain MRI on day 10 revealed cytotoxic edema in the white matter. On the midline sagittal T1-weighted image, there was diffuse low signal in the supratentorial white matter. On the T2-weighted images, signal intensities were increased in the white matter in a patchy distribution. The most prominent abnormalities were in the periventricular white matter, in the middle cerebellar peduncles, and around the dentate nuclei. The apparent diffusion coefficient in the white matter was consistently lower than that of a healthy control subject of the same age. Using in vivo proton magnetic resonance spectroscopy, approximately 8 mmol galactitol per kilogram of brain tissue was detected.

Biological basis

Etiology and pathogenesis

Carbohydrates are involved in many cellular processes, including the following: (1) energy production, storage, and transport; (2) regulation of glycemia (insulin/glucagon cycle); (3) fermentation processes; (4) regulation of cholesterol and triglyceride; and (5) glycan synthesis and glycosylation. Glycans are needed for the following: (1) lipid modulation and glycolipid synthesis; (2) glycocalyx formation (ie, a gel-like layer covering the luminal surface of vascular endothelial cells); (3) cell-extracellular matrix adhesion; (4) cell-cell interaction and communication; (5) immune response modulation; (6) protein modulation and glycoprotein synthesis; (7) enzyme activity control; (8) hormonal activity; and (9) receptor activity and intracellular signaling. In addition, glycoconjugates are involved in the pathogenesis of a wide array of pathological conditions, including inflammation, cancer, degenerative neuromuscular disorders, and diabetes.

Lactose. Lactose is a disaccharide composed of two monosaccharides: galactose and glucose.

The enzyme lactase is essential to the complete digestion of whole milk, splitting the disaccharide lactose into its component monosaccharides. Lactase is located in the brush border of the small intestine of humans and other mammals.

With congenital lactase deficiency (congenital alactasia), infants are unable to break down lactose in breastmilk or formula. If affected infants are not given a lactose-free infant formula, they develop severe diarrhea with resulting severe dehydration and weight loss.

Adult lactose intolerance is typically caused by reduced production of lactase after infancy (lactase nonpersistence). When such individuals consume lactose-containing dairy products, they develop abdominal cramps, pain, bloating, flatulence, nausea, and diarrhea beginning 30 minutes to 2 hours later. Treatment focuses on avoidance of dairy products, use of lactose-free products, or the use of lactase supplements.

Most people with lactase nonpersistence retain some lactase activity and can consume some lactose without experiencing symptoms. Affected individuals typically have difficulty digesting fresh milk but can eat modest amounts of dairy products (eg, cheese or yogurt) without discomfort because these foods are made with fermentation processes that break down much of the lactose.

D-galactose. Galactose (sometimes abbreviated Gal) is a monosaccharide sugar that is about as sweet as glucose and about two thirds as sweet as sucrose. It is an aldohexose and a C-4 epimer of glucose.

Galactose exists in both open-chain and cyclic forms. The open-chain form has a carbonyl at the end of the chain. Four isomers are cyclic: two with a pyranose (6-membered) ring and two with a furanose (5-membered) ring. The open-chain and cyclic forms can interconvert.

The metabolism of dietary disaccharides (lactose and sucrose). The principal dietary disaccharides are lactose, sucrose, and maltose (Table 1). Disturbed metabolism of the disaccharides is by far the most serious with the galactose component of lactose, resulting in forms of galactosemia. Dietary lactose is converted to its component monosaccharides in the small intestine (brush border), and these then enter the blood. From there, they are distributed to the liver, brain, and other organs. Under normal circumstances, the galactose is metabolized to glucose-1-phosphate, which can then be used in glycogenesis or metabolized to pyruvate through the glycolysis metabolic pathway.

Table 1. The Principal Dietary Disaccharides

Catabolism of d-galactose (the Leloir pathway). The Leloir pathway is a metabolic pathway for the catabolism of D-galactose. It is named after Argentine physician and biochemist Luis Federico Leloir (1906–1987) (136; 25; 26; 81; 79; 80; 98; 42; 61).

Catabolism of d-galactose through the Leloir pathway proceeds in four enzymatic steps: (1) the enzyme galactose mutarotase catalyzes the conversion of β-D-galactose to alpha-D-galactose; (2) alpha-D-galactose is phosphorylated by galactokinase (GALK) to galactose-1-phosphate; (3) D-galactose-1-phosphate uridylyltransferase (GALT) converts galactose-1-phosphate to UDP-galactose using UDP-glucose as the uridine diphosphate source; (4) UDP-galactose 4-epimerase (GALE) recycles the UDP-galactose to UDP-glucose for the transferase reaction. In addition, phosphoglucomutase converts the D-glucose 1-phosphate to D-glucose 6-phosphate.

In 1970, Leloir was awarded the Nobel Prize in Chemistry for this work.

Catabolism of d-galactose (the alternate pathway). In addition to the Leloir pathway, there is an alternate pathway to the pentose phosphate pathway via galactonate (30).

A combined scheme of galactose catabolism. A scheme of galactose metabolism includes the Leloir and alternate pathways of galactose catabolism as well as the linkages with glycosylation, glycogen synthesis, glycolysis and the tricarboxylic cycle, and the pentose phosphate pathway. In addition, some galactitol is formed by the action of aldose reductase on galactose; under normal circumstances, this is excreted in the urine.

Glycosylation pathways involving galactose. Galactose is metabolized into UDP-Gal, which is used as a precursor for glycosylation of different macromolecules. Galactose is a component of both N-glycan structures and the four types of human mucin O-glycans.

Galactosemia. Individuals with a profound deficiency of GALT can phosphorylate ingested galactose but fail to metabolize galactose-1-phosphate (64). As a consequence, galactose-1-phosphate and galactose accumulate, and the alternate pathway metabolites, galactitol and galactonate, are formed. Cataract formation can be explained by galactitol accumulation. The pathogenesis of the hepatic, renal, and cerebral disturbances is less clear but is probably related to the accumulation of galactose-1-phosphate; galactitol may play a role as well, especially in brain edema (11). However, the mechanisms of the disease are far from clear (29; 33; 153; 93).

Hypergalactosemia may be associated with deficiencies of the following three enzymes, all of which are from the Leloir pathway.

• Galactokinase (GALK) converts galactose to galactose-1-phosphate.
• Galactose-1-phosphate uridyltransferase (GALT) catalyzes conversion of galactose-1-phosphate and UDP-glucose to UDP-galactose and glucose-1-phosphate.
• Uridine diphosphate (UDP) galactose-4-epimerase (GALE) epimerizes UDP galactose to UDPglucose.

GALT is primarily responsible for classic hereditary galactosemia. Individuals with GALT deficiency manifest abnormal galactose tolerance.

Galactose-1-phosphate uridyltransferase (GALT) deficiency. Reichardt and Berg cloned the first cDNA encoding human GALT in 1988 (109). Over 300 mutations or polymorphisms of the GALT gene have now been reported (82; 39; 137; 24). Classic galactosemia is caused by a severe deficiency in GALT that is transmitted as an autosomal recessive trait. The GALT gene is located on chromosome 9p13. The gene for GALT is located on chromosome 9p13. It has 11 exons and contains approximately 4.3 kb of genomic DNA. Almost 90% of mutant alleles in classic galactosemia are due to the following four severe mutations.

Galactokinase (GALK) deficiency. The human GALK1 gene is located on chromosome 17q24. The enzyme catalyzes the first step in galactose metabolism, and its deficiency, although rare, results in cataracts in infancy.

Uridine diphosphate galactose-4´-epimerase (GALE) deficiency. GALE deficiency galactosemia is also known as epimerase deficiency galactosemia. The human GALE gene is located on chromosome 1p36.

Epidemiology

The prevalence of galactosemia due to GALT deficiency is approximately 1 case per 40,000 to 60,000 persons in the United States. Internationally, the prevalence varies widely (ie, 1 case in 70,000 people in the United Kingdom; 1 case in 16,476 people in Ireland). Galactosemia occurs in all races, although it is reportedly much less common in Asians.

Differential diagnosis

Confusing conditions

The clinical presentation of galactosemia overlaps with that of other galactose-related congenital disorders of glycosylation and galactose-related lysosomal storage disorders (30).

The differential diagnosis for galactosemia includes:

Galactokinase deficiency

Clinical presentation. Cataracts are the only consistent manifestation of the untreated disorder, though pseudotumor cerebri has been described (48; 22; 47). Liver, kidney, and brain damage, as seen in transferase deficiency, are not features of untreated galactokinase deficiency, and hypergalactosemia and increased galactose and galactitol excretion are the only chemical signs.

Metabolic derangement. Persons with GALK deficiency lack the ability to phosphorylate galactose. Consequently, nearly all of the ingested galactose is excreted, either as such or as its reduced metabolite, galactitol, formed by aldose reductase. As in GALT deficiency, cataracts result from the accumulation of galactitol in the lens, causing osmotic swelling of lens fibers and denaturation of proteins.

Genetics. The mode of inheritance is autosomal recessive. In most parts of Europe, in the United States, and in Japan, birth incidence is in the order of 1 in 150,000 to 1 million. It is higher in the Balkan countries, the former Yugoslavia, Romania, and Bulgaria, where it favors the Romani population, in whom the birth incidence was calculated as 1 in 2500.

The gene GK1, which encodes galactokinase, is located on chromosome 17q24. Many GK1 mutations have now been described. The GK1 P28T mutation was identified as the founder mutation responsible for galactokinase deficiency in the Romani from eastern European regions and in immigrants from Bosnia in Berlin (62). Different mutations have been documented (97).

Diagnostic tests. Provided they have been fed breastmilk or a lactose-containing formula prior to the test, newborns with the defect are discovered by newborn screening methods for detecting elevated blood galactose. If they have been fed glucose-containing fluid, the screening test could be false-negative. Every person with nuclear cataracts ought to be examined for GALK deficiency. Final diagnosis is made by assaying GALK activity in red blood cell lysates (88).

Treatment and prognosis. Treatment may be limited to the elimination of milk and dairy products from the diet. Minor sources of galactose, such as fruit, vegetables, and legumes, can probably be disregarded. When diagnosis is made rapidly and treatment begun promptly (during the first 2 to 3 weeks of life), cataracts can clear. When treatment is late and the cataracts are too dense, they will not clear completely (or at all) and must be removed surgically.

As in carriers with GALT deficiency, the speculation that heterozygosity for GALK deficiency predisposes to the formation of presenile cataracts remains unproven. It has been suggested that heterozygotes restrict their milk intake, though scientific proof of the merits of this measure is lacking.

Uridine diphosphate-galactose-4'-epimerase deficiency

Clinical presentation. This disorder exists in at least two forms (149; 47), both of which are discovered through newborn screening using suitable tests sensitive to both galactose and galactose-1-phosphate in dried blood spots. However, there are patients with intermediate levels of residual GALE activity, and it is unclear whether these subjects have disease-causing mutations (99). In five patients from three families with the severe form of the disorder, the enzyme defect was subtotal (149). The newborns presented with vomiting, jaundice, and hepatomegaly reminiscent of untreated classical galactosemia. All had galactosuria and hyperaminoaciduria, one had cataracts, and one had sepsis. In some, there was evidence for sensorineural deafness or dysmorphic features, but it is unclear whether this is related to solely to GALE deficiency because there was a high degree of consanguinity in the families of Pakistani/Asian ancestry with homozygosity for the V94M GALE gene mutation. An additional patient from India was reported (118).

Infants with the mild form appear healthy. The enzyme defect is incomplete. Lactose-fed newborns with the mild form detected in newborn screening are healthy and have neither hypergalactosemia nor galactosuria or hyperaminoaciduria.

Metabolic derangement. The GALE enzyme deficiency provokes an accumulation of UDP-galactose after milk feeding. This build-up also results in the accumulation of galactose-1-phosphate.

Genetics. Epimerase deficiency is inherited as an autosomal recessive trait. The epimerase gene resides on chromosome 1. Several mutations have been identified and characterized, including the V94M mutation that was present in a homozygous form in all of the patients tested with a severe phenotype (154). It is also well established that this enzyme catalyzes the conversion of UDP-N-acetylglucosamine to UDP-N-acetylgalactosamine. A compound heterozygous patient (L183P/N34S) of mixed Pakistani/Caucasian ancestry with a mild form and mental retardation, which may or may not be related to the underlying GALE deficiency, has been reported. As in GALT deficiency, abnormal glycosylation of proteins that appears to be dependent, at least in part, on lactose consumption has been reported in severe GALE deficiency and is thought to be a secondary biochemical complication, not primarily related to the genetic defect.

Diagnostic tests. The deficiency should be suspected when red cell galactose-1-phosphate is measurable while GALT is normal. Diagnosis is confirmed by the assay of epimerase in erythrocytes. Diagnosis of the severe form is based on the clinical symptoms, chemical signs, and more marked deficiency of epimerase in red cells. The utility of studying the enzyme deficiency in whole white cell pellets, isolated lymphocytes, and EBV-transformed lymphoblasts in potentially clinically relevant variant cases is under scrutiny.

Treatment and prognosis. The child with the severe form of epimerase deficiency is unable to synthesize galactose from glucose and is, therefore, galactose dependent. Dietary galactose in excess of actual biosynthetic needs will cause accumulation of UDP-galactose and galactose-1-phosphate, the latter being one presumptive toxic metabolite. When the amount of ingested galactose does not meet biosynthetic needs, synthesis of galactosylated compounds, such as galactoproteins and galactolipids, is impaired. As there is no easily available chemical parameter on which to base the daily galactose allowance (such as blood phenylalanine in phenylketonuria), treatment is extremely difficult. Children known to suffer from the disorder have impaired psychomotor development.

Infants with the mild form of epimerase deficiency described thus far have not required treatment, but it is advisable that one or two urine specimens be examined for reducing substances and aminoaciduria within a couple of weeks after diagnosis, while the infant is still being fed milk.

Fanconi-Bickel syndrome

This is a recessively inherited disorder of glucose and galactose transport due to GLUT2 deficiency and is extremely rare (117). Several cases have been discovered during newborn screening for galactose in blood.

Portosystemic venous shunting and hepatic arteriovenous malformation

Portosystemic bypass of splanchnic blood via ductus venosus Arantii or intrahepatic shunts cause alimentary hypergalactosemia, which may be discovered during metabolic newborn screening (49; 07; 70).

Diagnostic workup

Consultation with a clinical biochemical geneticist or metabolic disease specialist is advisable for diagnostic laboratory evaluation, monitoring, and clinical care of patients with galactosemia.

Galactosemia is most often diagnosed in infancy by newborn screening because all states in the U.S. include galactosemia as part of their newborn screen; however, methods are not uniform (10; 108). Variant forms of galactosemia can present later.

A positive (abnormal) result on the newborn screen must be followed by a quantitative erythrocyte galactose-1-phosphate uridyltransferase (GALT) analysis by a laboratory that routinely performs biochemical genetic testing and consultation (87; 88). In the pre-molecular diagnostic era, a GALT isoelectric-focusing electrophoresis test helped distinguish variant forms such as the Duarte defect (38; 89).

GALT genotyping usually provides a specific molecular diagnosis. The most common GALT allele in Caucasians is the Q188R mutation (approximately 65% of mutant alleles). The patients with a Q188R/Q188R genotype may have no residual GALT enzyme activity in erythrocytes (87). The S135L mutation is common in African Americans (77). The K285N mutation is common in Eastern Europe (90).

A urine-reducing substances test may be helpful. This test's results are almost always abnormal (positive) in infants with galactosemia who are ingesting lactose. This is a tube test rather than a dipstick test and must be differentiated from the routine urine dipstick test for glucose.

Patients with galactosemia may exhibit white matter abnormalities on MRI of the brain (69); uncommonly, cerebellar atrophy may also be present. Pseudotumor cerebri and lethal cerebral edema have been detected in the newborn period (63; 06; 94). In sick neonates, white matter edema may be associated with brain galactitol accumulation (12).

Infants with galactosemia can become jaundiced. Hyperbilirubinemia is often unconjugated but can become conjugated later.

Urine examination reveals evidence of albuminuria and, later, a generalized aminoaciduria. Eliminating lactose-containing formula from the diet quickly resolves the albuminuria.

Fatty infiltration and inflammatory changes initially may occur in the liver. Portal hypertension and pseudoacinar formation occur in later stages. Cirrhosis occurs in the final stage and is indistinguishable from other causes.

Leptin levels may be altered in galactosemia (71).

Leptin is a hormone predominantly made by adipose cells and enterocytes in the small intestine. It helps to regulate energy balance by inhibiting hunger, which, in turn, diminishes fat storage in adipocytes.

Management

A more uniform and evidence-based medical approach to dietary therapy and disease management after infancy are needed (21; 76; 66; 151). Treatment is generally focused on dietary therapy and management of complications. Drug therapy is not currently part of the standard of care for this condition.

Postnatal care. The mainstay of medical care in the postnatal period is to immediately discontinue breastfeeding and ingestion of lactose-containing formula. This ameliorates the acute toxicity in the neonatal period but does not prevent all long-term complications.

Clotting abnormalities may be cryptic and require fresh frozen plasma treatments.

Galactosemia should be high on the differential diagnosis of term infants with E coli sepsis. Workup for sepsis and use of antibiotics must be employed as indicated.

Chronic dietary therapy. A lactose-restricted diet must be provided for infants with galactosemia. Most metabolic specialists support a lifelong diet therapy, although older patients may tolerate lactose better than infants. Rare reports of patients with severe galactosemia off dietary therapy since childhood have raised questions about whether lactose restriction needs to be maintained after infancy (23; 101). Liberalizing galactose intake in older patients has been reported to improve the glycan structures in circulating IgG molecules (31; 72; 129).

Because dietary therapy is generally necessary, patients need to be followed by a dietitian who has experience with metabolic disorders. Dietary therapy requires both parental and patient education. Children should be involved in their dietary management as soon as appropriate.

Totally eliminating galactose is difficult because it is present in a wide variety of foods (infant foods, fruits, vegetables), especially in the macromolecular form (01). It does not appear to be reasonable to restrict fruits and vegetables, only cow’s milk and dairy products (138). The restriction of milk intake throughout life is controversial.

Complications may be related to endogenous production of galactose as galactose-1-phosphate and galactitol levels remain elevated despite strict adherence to a lactose-restricted diet (14; 13; 120). Not surprisingly, as patients maintain steady-state levels of galactose metabolites in blood and urine, even patients with absent GALT activity are capable of oxidizing galactose to CO2 (15; 08; 16).

Because many patients develop abnormalities of bone mineral density with abnormal fragility, calcium and vitamin D intake should be monitored (147; 140).

Management of complications. During the initial hospitalization of a child with symptomatic, severe classic galactosemia, the major concerns are sepsis, bleeding, liver dysfunction, and brain swelling. These conditions are to be treated as they would be in patients who do not have galactosemia. Immediate and total removal of lactose from the diet is the only specific treatment for a patient with galactosemia that differs from treatments for patients with sepsis or liver dysfunction from other causes.

Chronic disease management requires time-dependent testing and consultations (148). The etiology of long-term complications is unknown (11).

Infants should be screened for speech and language deficits between 7 to 12 months of age; additional screening should then be performed at 2, 3, and 5 years of age (105; 84). Affected infants and children should then be referred to appropriate speech and language centers (134; 86); optimal individualized treatment is necessary to help address learning problems.

Adolescent females should be referred to an adolescent medicine specialist or endocrinologist and women to a reproductive gynecologist for appropriate treatment for primary ovarian insufficiency (128). Fertility preservation requires careful consideration as ethical concerns exist (139). Males do not appear to manifest severe primary gonadal disease (113; 56).

No standardized treatment for short stature has been established, and the etiology is unknown in most instances.

Gastrointestinal tract dysfunction may be more common during the lifetime of the patient (126).

Outcomes

If untreated, classic galactosemia is a life-threatening disorder. Infants with classic galactosemia who are severely ill (eg, those with sepsis, coagulopathy, or liver dysfunction) before dietary treatment for galactosemia is initiated may develop permanent liver, brain, or eye damage (although cataracts may be completely reversible). Most patients with severe galactosemia who do not receive treatment probably do not survive the newborn period.

Fortunately, most developed countries screen for galactosemia in the newborn period, and infants affected with classic galactosemia are treated before they become very ill. Following the institution of a galactose-restricted diet, most patients appear to reach adulthood. Even with appropriate dietary therapy, most patients with classic disease have long-term complications, including delayed language acquisition, speech defects, learning problems, decreased bone mineral density, and hypergonadotropic hypogonadism. Less common are short stature, poor growth, tremors, ataxia, and dystonia (147).

Patients with clinical variant galactosemia with higher residual GALT enzyme activities may not develop these long-term complications (10; 115).

Duarte variant galactosemia has a benign course. Duarte galactosemia is not associated with adverse developmental outcomes in children aged 6 to 12 years compared to children without Duarte galactosemia, and milk exposure during infancy is not associated with adverse developmental outcomes in children with Duarte galactosemia (27; 43). Therefore, dietary therapy is often not recommended (and likely not necessary) for this variant (27).

Special considerations

Pregnancy

Galactose restriction in the pregnant woman with a fetus with classic galactosemia does not appear to produce beneficial effects in the offspring (74; 41; 75; 145).

There have been over 20 pregnancies reported in women with galactosemia (145; 09; 54).