Genetics | Easy Pediatrics

Patau syndrome – Trisomy 13

Jul 302012

Patau syndrome, also known as trisomy 13 and trisomy D, is a chromosomal abnormality, a syndrome in which a patient has an additional chromosome 13 due to a nondisjunction of chromosomes during meiosis.

Causes

Trisomy 13 occurs when extra DNA from chromosome 13 appears in some or all of the body’s cells.

Trisomy 13 — the presence of an extra (third) chromosome 13 in all of the cells.
Trisomy 13 mosaicism — the presence of an extra chromosome 13 in some of the cells.
Partial trisomy — the presence of a part of an extra chromosome 13 in the cells.

Incidence

Patau syndrome is the least common and most severe of the viable autosomal trisomies.

Trisomy 13 occurs in about 1 out of every 10,000 newborns.

Median survival is fewer than 3 days, with only one in 20 children surviving longer than 6 months.

The sex ratio at birth is slightly skewed toward females, presumably because of decreased survival among males.

Clinical Presentation

Newborns with Patau syndrome typically present in the neonatal period with low Apgar scores and may have the following conditions:
- Cleft lip
- Cleft palate
- Polydactyly (postaxial)
- Microcephaly
- Rocker-bottom feet
- Microphthalmia Continue reading »

Rating: 10.0/10 (2 votes cast)

Rating: +1 (from 1 vote)

Tay-Sachs disease

Genetics, Metabolic Disorders No Responses »

Aug 122011

The most common of the lipid storage diseases, Tay-Sachs disease results from a congenital deficiency of the enzyme hexosaminidase A. It’s characterized by progressive mental and motor deterioration and is usually fatal before age 5, although some adolescents and adults with variations of hexosaminidase A deficiency have been noted.

Causes

Tay-Sachs disease (also known as GM₂ gangliosidosis) is an autosomal recessive disorder in which the enzyme hexosaminidase A is virtually absent or deficient. This enzyme is necessary for metabolism of gangliosides, water-soluble glycolipids found primarily in central nervous system (CNS) tissues. Without hexosaminidase A, accumulating lipid pigments distend and progressively destroy and demyelinate CNS cells.

Tay-Sachs disease strikes persons of Eastern European Jewish (Ashkenazi) ancestry more often than the general population, occurring in about 1 in 2,500 live births in this ethnic group. About 1 in 25 Ashkenazi Jews are heterozygous carriers.

Signs and symptoms

A neonate with classic Tay-Sachs disease appears normal at birth, although he may have an exaggerated Moro reflex. By age 3 to 6 months, he becomes apathetic and responds only to loud sounds. His neck, trunk, arm, and leg muscles grow weaker, and soon he can’t sit up or lift his head. He has difficulty turning over, can’t grasp objects, and has progressive vision loss.

By age 18 months, the infant is usually deaf and blind and has seizures, generalized paralysis, and spasticity. His pupils are dilated and don’t react to light. Decerebrate rigidity and a vegetative state follow. The child suffers recurrent bronchopneumonia after age 2 and usually dies before age 5. A child who survives may develop ataxia and progressive motor retardation between ages 2 and 8.

The “juvenile” form of Tay-Sachs disease generally appears between ages 2 and 5 as a progressive Continue reading »

Rating: 5.5/10 (4 votes cast)

Rating: +2 (from 2 votes)

Diagnosing autistic disorder

Genetics, Neurology No Responses »

Jul 212011

Autism is diagnosed when the patient meets the criteria in the Diagnostic and Statistical Manual of Mental Disorders, 4th edition – Text Revision. At least six characteristics from the following three categories must be present, including at least two from the social interaction category and one each from the communication and patterns categories.

Social interaction

Patient displays impairment in social interaction, as shown by at least two of the following:

marked impairment in the use of multiple nonverbal behaviors, such as eye-to-eye gaze, facial expression, body postures, and gestures to regulate social interaction
failure to develop peer relationships appropriate to developmental level
no spontaneous sharing of enjoyment, interests, or achievements with others
lack of social or emotional reciprocity
gross impairment in ability to make peer friendships.

Communication

Patient displays impairment in communication, as shown by at least one of the following:

delay in or total lack of development of spoken language
in individuals with adequate speech, marked impairment in initiating or sustaining a conversation with others
stereotyped and repetitive use of language or idiosyncratic language
lack of varied, spontaneous make-believe play or social imitative play appropriate to developmental level.

Patterns

Patient displays restricted, repetitive, and stereotyped patterns of behavior, interests, and Continue reading »

Rating: 10.0/10 (1 vote cast)

Rating: +1 (from 1 vote)

Page 1 of 412 3 4 »