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2025 ICD-10-CM code Q90.1

Trisomy 21, mosaicism (mitotic nondisjunction).

Refer to the official ICD-10-CM coding guidelines for proper application of this code.Always code the associated conditions and intellectual disability if present.Use additional codes to specify the level of intellectual disability.

Medical necessity for diagnostic testing and management of Q90.1 is based on the clinical presentation, the need for early intervention to address developmental delays, and the potential for associated medical complications.Documentation should support the need for specific diagnostic tests and treatment plans based on the patient's individual needs.

The clinical responsibility for a patient with Q90.1 includes genetic counseling, comprehensive medical evaluation (cardiovascular, gastrointestinal, endocrine, etc.), developmental assessment, and management of associated conditions.Ongoing monitoring and support are crucial throughout the patient's life.

IMPORTANT:Q90.0 (Trisomy 21, nonmosaicism), Q90.2 (Trisomy 21, translocation), Q90.9 (Down syndrome, unspecified).Additional codes may be necessary to specify associated conditions (e.g., congenital heart defects) or intellectual disability.

In simple words: This code describes a type of Down syndrome where some cells have an extra copy of chromosome 21, while others do not. This means that the symptoms can vary greatly from person to person, ranging from mild to severe developmental delays and physical features.

Trisomy 21, mosaicism (mitotic nondisjunction) is a chromosomal abnormality characterized by the presence of an extra copy of chromosome 21 in some but not all cells of the body.This mosaicism arises from a mitotic nondisjunction event after fertilization, resulting in a mixture of cells with a normal chromosome complement and cells with trisomy 21.The clinical manifestations can vary widely depending on the proportion of affected cells, ranging from mild to severe intellectual disability, characteristic facial features (e.g., upslanting palpebral fissures, epicanthic folds), hypotonia, congenital heart defects, and other associated medical conditions.

Example 1: A newborn infant is diagnosed with Trisomy 21, mosaicism through karyotype analysis revealing a mixture of cells with 46 chromosomes and 47 chromosomes. The infant exhibits hypotonia and some characteristic facial features., A 5-year-old child with previously diagnosed mosaic Down syndrome presents with a cardiac murmur. Echocardiography confirms an atrioventricular septal defect, requiring further cardiology consultation and management., A young adult with mosaic Down syndrome is experiencing increased cognitive decline. This warrants assessment for early-onset Alzheimer's disease and appropriate supportive care.

Karyotype analysis demonstrating mosaicism for trisomy 21. Detailed clinical evaluation including physical examination, assessment of developmental milestones, and investigations for associated medical conditions (e.g., echocardiogram, hearing assessment).Documentation of family history of chromosomal abnormalities.

** The severity of symptoms in mosaic Down syndrome is highly variable and depends on the percentage of affected cells.Careful clinical assessment is essential for proper diagnosis and management.

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