Neu–Laxova syndrome (NLS, also known as Neu syndrome; Neu-Povýsilová syndrome; or 3-phosphoglycerate dehydrogenase deficiency, neonate form) is a rare

autosomal recessive In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the Phenotype, effect of a different variant of the same gene on Homologous chromosome, the other copy of the chromosome. The firs ...

disorder characterized by severe

intrauterine growth restriction Intrauterine growth restriction (IUGR), or fetal growth restriction, is the poor growth of a fetus while in the womb during pregnancy. IUGR is defined by clinical features of malnutrition and evidence of reduced growth regardless of an infant's ...

and multiple

congenital malformations A birth defect is an abnormal condition that is present at birth, regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can range from mild to severe. Birth de ...

. Neu–Laxova syndrome is a very severe disorder, leading to

stillbirth Stillbirth is typically defined as fetus, fetal death at or after 20 or 28 weeks of pregnancy, depending on the source. It results in a baby born without vital signs, signs of life. A stillbirth can often result in the feeling of guilt (emotio ...

or death shortly after birth. It was first described by Dr. Richard Neu in 1971 and Dr. Renata Laxova in 1972 as a lethal disorder in siblings with multiple malformations. Neu–Laxova syndrome is an extremely rare disorder with fewer than 100 cases reported in medical literature.

Signs and symptoms

Neu-Laxova syndrome presents with severe malformations leading to prenatal or neonatal death. Typically, NLS involves characteristic facial features, decreased fetal movements and skin abnormalities. Fetuses or newborns with Neu–Laxova syndrome have typical facial characteristics which include

proptosis Exophthalmos (also called exophthalmus, exophthalmia, proptosis, or exorbitism) is a bulging of the eye anteriorly out of the orbit. Exophthalmos can be either bilateral (as is often seen in Graves' disease) or unilateral (as is often seen in ...

(bulging eyes) with eyelid malformations, nose malformations, round and gaping mouth, micrognathia (small jaw) and low set or malformed ears. Additional facial malformations may be present, such as

cleft lip A cleft lip contains an opening in the upper lip that may extend into the nose. The opening may be on one side, both sides, or in the middle. A cleft palate occurs when the palate (the roof of the mouth) contains an opening into the nasal cavi ...

cleft palate A cleft lip contains an opening in the upper lip that may extend into the nose. The opening may be on one side, both sides, or in the middle. A cleft palate occurs when the palate (the roof of the mouth) contains an opening into the nose. The ...

. Limb malformations are common and involve the fingers (

syndactyly Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammals, but is an unusual condition in humans. The term is . Classification Syndactyly can be simple or complex. * In simple syndactyly, adja ...

), hands, or feet. Additionally,

edema Edema (American English), also spelled oedema (British English), and also known as fluid retention, swelling, dropsy and hydropsy, is the build-up of fluid in the body's tissue (biology), tissue. Most commonly, the legs or arms are affected. S ...

and flexion deformities are often present. Other features of NLS are severe

, skin abnormalities (

ichthyosis Ichthyosis is a family of genetic disorder, genetic skin disorders characterized by Xeroderma, dry, Scleroderma, thickened, scaly skin. The more than 20 types of ichthyosis range in severity of symptoms, outward appearance, underlying genetic cau ...

and

hyperkeratosis Hyperkeratosis is thickening of the stratum corneum (the outermost layer of the epidermis, or skin), often associated with the presence of an abnormal quantity of keratin,Kumar, Vinay; Fausto, Nelso; Abbas, Abul (2004) ''Robbins & Cotran Pathol ...

) and decreased movement. Malformations in the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain, spinal cord and retina. The CNS is so named because the brain integrates the received information and coordinates and influences the activity o ...

are frequent and may include

microcephaly Microcephaly (from Neo-Latin ''microcephalia'', from Ancient Greek μικρός ''mikrós'' "small" and κεφαλή ''kephalé'' "head") is a medical condition involving a smaller-than-normal head. Microcephaly may be present at birth or it m ...

lissencephaly Lissencephaly (, meaning 'smooth brain') is a set of rare brain disorders whereby the whole or parts of the surface of the brain are smooth. It is caused by defective neuronal migration during the 12th to 24th weeks of gestation, resulting in a ...

microgyria In neuroanatomy, a microgyrus is an area of the cerebral cortex that includes only four cortical layers instead of six. Microgyria are believed by some to be part of the genetic lack of prenatal development which is a cause of, or one of the cau ...

, hypoplasia of the cerebellum and

agenesis of the corpus callosum Agenesis of the corpus callosum (ACC) is a rare birth defect in which there is a complete or partial absence of the corpus callosum. It occurs when the development of the corpus callosum, the band of white matter connecting the two hemispheres ...

. Other malformations may also be present, such as

neural tube defect Neural tube defects (NTDs) are a group of birth defects in which an opening in the spine or cranium remains from early in human development. In the third week of pregnancy called gastrulation, specialized cells on the dorsal side of the embryo ...

Genetics

Neu-Laxova syndrome is a heterogeneous

metabolic disorder A metabolic disorder is a disorder that negatively alters the body's processing and distribution of macronutrients, such as proteins, fats, and carbohydrates. Metabolic disorders can happen when abnormal chemical reactions in the body alter the ...

caused by

homozygous Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. Mos ...

or compound heterozygous mutations in one of three genes: '' PHGDH'', '' PSAT1'' and '' PSPH'' These genes are involved in the serine biosynthesis pathway and are essential for

cell proliferation Cell proliferation is the process by which ''a cell grows and divides to produce two daughter cells''. Cell proliferation leads to an exponential increase in cell number and is therefore a rapid mechanism of tissue growth. Cell proliferation ...

. Mutations in all three genes had been previously identified as the cause of serine-deficiency syndromes. Although there is some clinical overlap between NLS and these neurometabolic disorders, the phenotype in other serine-deficiency disorders is milder.

Diagnosis

The diagnosis is usually based on clinical features present at birth. Ultrasound in the second trimester may show abnormalities associated with NLS, including

polyhydramnios Polyhydramnios is a medical condition describing an excess of amniotic fluid in the amniotic sac. It is seen in about 1% of pregnancies. It is typically diagnosed when the amniotic fluid index (AFI) is greater than 24 cm. There are two clini ...

and decreased fetal motility.

Treatment

Serine Serine (symbol Ser or S) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α- amino group (which is in the protonated − form under biological conditions), a carboxyl group (which is in the deprotonated − ...

and

glycine Glycine (symbol Gly or G; ) is an amino acid that has a single hydrogen atom as its side chain. It is the simplest stable amino acid. Glycine is one of the proteinogenic amino acids. It is encoded by all the codons starting with GG (G ...

supplementation has shown tentative benefits in those with related serine biosynthesis defects and milder forms of NLS.

Prognosis

The prognosis is poor; affected individuals are either

stillborn Stillbirth is typically defined as fetal death at or after 20 or 28 weeks of pregnancy, depending on the source. It results in a baby born without signs of life. A stillbirth can often result in the feeling of guilt or grief in the mother. T ...

or die shortly after birth. The longest survival reported in the literature is 134 days. This syndrome is transmitted as an

disorder and there is a risk for recurrence of 25% in future pregnancies.

References

External links

{{DEFAULTSORT:Neu-Laxova syndrome Autosomal recessive disorders Congenital disorders Disorders related to length of gestation and fetal growth Syndromes with cleft lip and/or palate Syndromes with craniofacial abnormalities Syndromes affecting the nervous system Syndromes with dysmelia Rare syndromes