48,XXYY syndrome

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

48,XXYY syndrome is a chromosomal condition that affects male development. There is a lot of variability in symptoms between people with 48,XXYY syndrome. Almost all affected individuals have developmental delays in infancy and develop decreased testosterone levels (hypogonadism) during adolescence. People with 48,XXYY syndrome are also at risk for other health problems.

Adolescents and adults with this condition usually have small testes that do not produce enough testosterone, which is the hormone that directs male sexual development. Without treatment, a shortage of testosterone during puberty can lead to reduced facial and body hair, poor muscle development, low energy levels, and an increased risk of breast enlargement (gynecomastia). Because their testes do not function normally, individuals with 48,XXYY syndrome have difficulty having biological children (a condition called infertility), but they may be able to have children using assisted reproductive technologies.

48,XXYY syndrome can affect other parts of the body as well. Affected individuals are often taller than their peers, with an average adult height of 6 feet, 4 inches (193 cm). They may develop a mild to moderate hand tremor that typically starts in adolescence and may increase with age. Dental problems are frequently seen in people with this condition, including delayed appearance of the primary (baby) or secondary (adult) teeth, thin tooth enamel, crowded or misaligned teeth, and multiple cavities.

Additionally, individuals with 48,XXYY syndrome may have flat feet (pes planus), elbow abnormalities, abnormal fusion of certain bones in the forearm (radioulnar synostosis), allergies, asthma, type 2 diabetes, seizures, congenital heart defects, and an inflammatory condition in the throat (esophagus) called eosinophilic esophagitis. As people with 48,XXYY get older, they may develop a narrowing of the blood vessels in the legs called peripheral vascular disease. Peripheral vascular disease can cause skin ulcers to form. Affected individuals are also at risk of developing a type of clot called a deep vein thrombosis that occurs in the deep veins of the legs.

Most individuals with 48,XXYY syndrome have an IQ score that ranges from 60 to 80 and have some degree of difficulty with speech and language development. The development of motor skills such as sitting, standing, and walking may be delayed in some children with 48,XXYY syndrome. They may also have poor coordination. Learning disabilities are very common in people with this disorder, especially in the areas of reading and written expression. People with 48,XXYY typically perform better at tasks focused on math, visual-spatial skills such as puzzles, and memorization of locations or directions. Affected individuals have higher-than-average rates of other neurodevelopmental and behavioral disorders, such as attention-deficit/hyperactivity disorder (ADHD); mood disorders, including anxiety and depression; and autism spectrum disorder, which affects communication and social interaction.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

48,XXYY syndrome is a condition related to the the sex chromosomes. People normally have 46 chromosomes in each cell. Two of the 46 chromosomes, known as X and Y, are called sex chromosomes because they help determine whether a person will develop male or female sex characteristics. Females typically have two X chromosomes (46,XX), and males have one X chromosome and one Y chromosome (46,XY). 48,XXYY syndrome results from the presence of an extra copy of both sex chromosomes in each of a male's cells (48,XXYY). Extra copies of genes on the X chromosome interfere with sexual development, preventing the testes from functioning normally and reducing the levels of testosterone.

Many genes are found only on the X or Y chromosome, but genes in areas known as the pseudoautosomal regions are present on both sex chromosomes. Extra copies of genes from the pseudoautosomal regions of the extra X and Y chromosome contribute to the signs and symptoms of 48,XXYY syndrome; however, the specific genes have not been identified. The presence of extra sex chromosomes can also lead to changes in activity of other genes in other chromosomes.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

48,XXYY is not inherited; it usually occurs as a random event during the formation of reproductive cells (eggs and sperm). An error in cell division called nondisjunction results in a reproductive cell with an abnormal number of chromosomes. In 48,XXYY syndrome, the extra sex chromosomes almost always come from a sperm cell. Nondisjunction may cause a sperm cell to gain two extra sex chromosomes, resulting in a sperm cell with three sex chromosomes (one X and two Y chromosomes). If that sperm cell fertilizes a normal egg cell with one X chromosome, the resulting child will have two X chromosomes and two Y chromosomes in each of the body's cells.

In a small percentage of cases, a normal sperm cell with one Y chromosome can fertilize a normal egg cell with one X chromosome, but right after fertilization, nondisjunction of the sex chromosomes causes the embryo to gain two extra sex chromosomes. This produces a 48,XXYY embryo.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

48,XXYY syndrome is estimated to affect 1 in 18,000 to 40,000 male newborns.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Abnormality of speech or vocalization · Very frequent (99-80%)

An abnormality in the sound (volume) or cadence (rate) of speech.

Azoospermia · Very frequent (99-80%)

Absence of any measurable level of sperm,whereby spermatozoa cannot be observed even after centrifugation of the semen pellet.

Decreased testicular size · Very frequent (99-80%)

Reduced volume of the testicle (the male gonad).

Global developmental delay · Very frequent (99-80%)

A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age.

Hypergonadotropic hypogonadism · Very frequent (99-80%)

Reduced function of the gonads (testes in males or ovaries in females) associated with excess pituitary gonadotropin secretion and resulting in delayed sexual development and growth delay.

Intellectual disability · Very frequent (99-80%)

The term intellectual disability or intellectual developmental disorder is used to describe significantly sub-average intellectual and adaptive functioning based on clinical assessment and as measured by individually administered, appropriately normed, standardized and validated tests of intellectual functioning and adaptive behavior, with onset during the developmental period from infancy through adolescence.

Infertility · Very frequent (99-80%)

Abnormality of dental enamel · Frequent (79-30%)

An abnormality of the dental enamel.

Other findings in the same source

From: Orphanet

Additional reported features include Abnormality of the shoulder (Frequent (79-30%)); Anxiety (Frequent (79-30%)); Asthma (Frequent (79-30%)); Attention deficit hyperactivity disorder (Frequent (79-30%)); Blepharophimosis (Frequent (79-30%)); Carious teeth (Frequent (79-30%)); Chronic otitis media (Frequent (79-30%)); Clinodactyly of the 5th finger (Frequent (79-30%)); Constipation (Frequent (79-30%)); Delayed eruption of teeth (Frequent (79-30%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing 48,XXYY syndrome is Clinical Genetics, with a clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with clinical geneticist referral.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Does the exact genetic or chromosome finding explain the observed features?
• Would a genetic counsellor help the family understand the result?
• Which organ-specific assessments are appropriate for this particular diagnosis?

Treatment discussions and follow-up

Where the source describes treatments, these are an overview of possible care, not a prescription for an individual. Ask which option applies to the confirmed diagnosis, what benefit is expected, what adverse effects to watch for and how progress will be assessed. Availability, approvals and local practice can differ from the country described in the source.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.