Q91.4 Trisomy 13, nonmosaicism (meiotic nondisjunction)

Name of the Condition

• Trisomy 13, nonmosaicism (meiotic nondisjunction)

Summary

Trisomy 13, nonmosaicism (meiotic nondisjunction) is a severe chromosomal disorder caused by the presence of an extra copy of chromosome 13 in all cells. This condition is associated with significant congenital anomalies and developmental delays. The severity of symptoms is typically life-limiting, with most affected individuals not surviving beyond the first year of life.

Causes

Trisomy 13, nonmosaicism results from meiotic nondisjunction, an error during the formation of reproductive cells (eggs or sperm) where chromosome 13 fails to separate properly. This leads to an embryo with three copies of chromosome 13 instead of the usual two. The error occurs randomly and is not typically inherited from parents, though rare cases may involve translocation.

Risk Factors

• Advanced maternal age.
• Previous pregnancy with a chromosomal abnormality.
• Family history of chromosomal disorders.

Symptoms

• Low birth weight and poor growth.
• Distinctive facial features (e.g., small head, cleft lip/palate, sloping forehead).
• Heart defects.
• Limb abnormalities (e.g., polydactyly, clenched fists).
• Neurological impairments and developmental delays.
• Eye defects (e.g., coloboma, microphthalmia).
• Abdominal wall defects (e.g., omphalocele).

Diagnosis

Prenatal diagnosis may involve ultrasound, amniocentesis, or chorionic villus sampling (CVS) to detect chromosomal abnormalities. Postnatal confirmation is achieved through karyotyping or chromosomal microarray analysis.

Treatment Options

Management focuses on supportive care, including addressing specific organ defects (e.g., cardiac surgery), nutritional support, and palliative care. Treatment plans are individualized based on the severity of symptoms and associated anomalies.

Prognosis and Follow-Up

The prognosis is poor, with most affected individuals not surviving beyond the first year of life. Follow-up care involves monitoring for complications and providing supportive care to manage symptoms and improve quality of life.

Complications

• Severe intellectual disability.
• Respiratory infections.
• Feeding difficulties.
• Seizures.
• Organ failure.

Lifestyle & Prevention

There are no known modifiable lifestyle factors to prevent this condition. Genetic counseling may be recommended for families with a history of chromosomal disorders.

When to Seek Professional Help

Seek medical attention if prenatal screening indicates a chromosomal abnormality or if an infant exhibits symptoms consistent with Trisomy 13, such as distinctive facial features, heart defects, or limb abnormalities.

Tips for Medical Coders

Document the presence of meiotic nondisjunction and nonmosaicism to support the use of code Q91.4. Ensure clinical documentation specifies the chromosomal abnormality and any associated congenital anomalies to accurately reflect the condition.