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Chapter 17: Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders (Q00–QA1)

Conditions present from birth: structural malformations of the heart and other organs, chromosomal conditions such as Down syndrome, and genetic disorders diagnosed in childhood.

Chapter 17 spans codes Q00–QA1 in the FY2027 ICD-10-CM tabular list. This guide explains 16 of its most common codes — select a code for its official description, a plain-English explanation and a note on when the code is used.

ICD-10 Chapter 17: Congenital & Genetic Disorders — illustrative image

Codes in this chapter

CodeOfficial descriptionIn plain words
Q21.0Ventricular septal defectA ventricular septal defect is a hole in the wall between the heart's two lower chambers, present from birth.
Q21.11Secundum atrial septal defectA secundum atrial septal defect is an opening in the wall between the heart's upper chambers, in its central (secundum) part.
Q21.12Patent foramen ovaleA patent foramen ovale is a small flap-like opening between the heart's upper chambers that failed to close after birth; very common and usually harmless.
Q21.3Tetralogy of FallotTetralogy of Fallot is a combination of four congenital heart defects causing reduced oxygen in the blood.
Q23.1Congenital insufficiency of aortic valveA congenital bicuspid aortic valve has two leaflets instead of the usual three, and can narrow or leak over time.
Q24.9Congenital malformation of heart, unspecifiedA congenital malformation of the heart recorded without the specific defect being stated.
Q25.0Patent ductus arteriosusA patent ductus arteriosus is a fetal blood vessel between the aorta and pulmonary artery that stays open after birth.
Q38.1AnkyloglossiaAnkyloglossia (tongue-tie) is a short band under the tongue restricting its movement, present from birth.
Q54.9Hypospadias, unspecifiedHypospadias is a birth condition in boys in which the urine opening is on the underside of the penis rather than the tip; type unspecified.
Q61.2Polycystic kidney, adult typeAutosomal dominant polycystic kidney disease (adult type) causes many cysts to grow in the kidneys over a lifetime, gradually reducing function.
Q61.3Polycystic kidney, unspecifiedPolycystic kidney disease means many cysts develop in the kidneys; the inheritance type is not specified here.
Q62.0Congenital hydronephrosisCongenital hydronephrosis is swelling of a baby's kidney from urine build-up behind a narrowed junction, present from birth.
Q64.2Congenital posterior urethral valvesCongenital posterior urethral valves are flaps of tissue in a baby boy's urethra that block urine flow and can damage the bladder and kidneys.
Q82.5Congenital non-neoplastic nevusA congenital non-neoplastic naevus is a birthmark present from birth that is not a tumour, such as many port-wine or pigmented birthmarks.
Q85.01Neurofibromatosis, type 1Neurofibromatosis type 1 is a genetic condition causing coffee-coloured skin patches and benign nerve tumours (neurofibromas).
Q90.9Down syndrome, unspecifiedDown syndrome is a genetic condition caused by an extra copy of chromosome 21, affecting development and learning; type unspecified.

This guide explains ICD-10-CM codes in plain language for patients, students and other readers. It is educational information only — not coding, billing or medical advice. The code recorded for any real encounter is assigned from the full clinical documentation by the treating team and qualified coders, and only they can decide which code fits a specific case.

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