48,XXYY Syndrome: Disease Overview

Etiology and Epidemiology

Cause:
48,XXYY syndrome is caused by chromosomal nondisjunction (failure of chromosomes to separate properly) during the formation of sperm or eggs. It is generally not inherited and usually occurs as a de novo chromosomal abnormality.

Prevalence:
It is estimated to occur in approximately 1 in 18,000 to 50,000 live male births.

Major Clinical Features

Clinical manifestations vary considerably among individuals, and not all individuals develop the same features. The following are among the clinical features frequently observed in individuals with 48,XXYY syndrome.

Cardiovascular System	・Congenital Heart Disease ・Varicose veins of the lower extremities ・Deep vein thrombosis (DVT)
Metabolic and Endocrine System	・Low testosterone levels (hypogonadism), which may result in delayed or incomplete development of secondary sexual characteristics ・Diabetes mellitus, particularly in association with insulin resistance ・Hypercholesterolemia
Neurological and Psychiatric Features	・Intellectual disability ・Symptoms of attention-deficit/hyperactivity disorder (ADHD) ・Symptoms of autism spectrum disorder (ASD) ・Difficulty regulating impulsivity and aggressive behavior ・Hand tremor resembling essential tremor
Genitourinary System	・Cryptorchidism (undescended testes) ・Impaired spermatogenesis, which may result in infertility
Gastrointestinal System	・Gastroesophageal reflux disease (GERD) ・Persistent chronic constipation
Respiratory System	・Pneumonia ・Asthma (bronchial asthma)
Immune System / Allergic Disorders	・Food allergies ・Atopic dermatitis ・Malignant lymphoma, including non-Hodgkin lymphoma
Musculoskeletal System	・Tall stature, particularly with disproportionately long legs ・Hypotonia (low muscle tone), including “floppy infant” presentation during infancy ・Radioulnar synostosis (partial fusion of the radius and ulna in the forearm) ・Osteoporosis, with an increased risk associated with low testosterone levels ・Pes planus (flat feet) ・Dental abnormalities, including enamel hypoplasia and taurodontism

Diagnosis and Treatment

Diagnosis:
A definitive diagnosis is made by chromosomal analysis of a blood sample, such as conventional karyotyping using G-banding (G-banded chromosome analysis).

Treatment:
There is currently no curative treatment that can correct the underlying chromosomal abnormality. Management is therefore individualized according to the patient’s clinical manifestations and associated conditions.

・Endocrine Therapy

From adolescence onward, testosterone replacement therapy may be indicated to promote the　　　 　　　　　　　　　　　　　　　development of secondary sexual characteristics and help maintain bone mineral density.

・Developmental and Educational Support

Early intervention with speech-language therapy (SLT) and occupational therapy (OT), among other supportive services, may help promote language development, social skills, and adaptive functioning.

・Prevention and Treatment of Complications

Screening, prevention, and treatment of associated complications should be provided by the appropriate medical specialists according to the individual’s clinical needs.

The information above is intended as a general overview of 48,XXYY syndrome. Individual symptoms, clinical features, and treatment needs may vary. Please consult your treating physician or an appropriate specialist for advice regarding your own diagnosis and treatment.