X-linked intellectual disability, Nascimento type

What it is

From: Orphanet

X-linked intellectual disability, Nascimento type is a rare X-linked intellectual disability syndrome characterized by intellectual disability (with severe speech impairment), a myxedematous appearance, dysmorphic facial features (including large head, synophrys, prominent supraorbital ridges, almond-shaped and deep-set eyes, large ears, wide mouth with everted lower lip and downturned lip corners), low posterior hairline, short, broad neck, marked general hirsutism and abnormal hair whorls, skin changes (e.g. dry skin or hypopigmented spots), widely spaced nipples, obesity, micropenis, onychodystrophy and seizures.

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.

Delayed gross motor development · Very frequent (99-80%)

A type of motor delay characterized by a delay in acquiring the ability to control the large muscles of the body for walking, running, sitting, and crawling.

Dry skin · Very frequent (99-80%)

Skin characterized by the lack of natural or normal moisture.

Low hanging columella · Very frequent (99-80%)

Columella extending inferior to the level of the nasal base, when viewed from the side.

Wide mouth · Very frequent (99-80%)

Distance between the oral commissures more than 2 SD above the mean. Alternatively, an apparently increased width of the oral aperture (subjective).

Poor speech · Very frequent (99-80%)

Abnormal cerebral white matter morphology · Frequent (79-30%)

An abnormality of the cerebral white matter.

Aggressive behavior · Frequent (79-30%)

Behavior or an act aimed at harming a person, animal, or physical property (e.g., acts of physical violence; shouting, swearing, and using harsh language; slashing someone's tires).

Broad neck · Frequent (79-30%)

Increased side-to-side width of the neck.

Chronic constipation · Frequent (79-30%)

Constipation for longer than three months with fewer than 3 bowel movements per week, straining, lumpy or hard stools, and a sensation of anorectal obstruction or incomplete defecation.

Depressed nasal bridge · Frequent (79-30%)

Posterior positioning of the nasal root in relation to the overall facial profile for age.

Downturned corners of mouth · Frequent (79-30%)

A morphological abnormality of the mouth in which the angle of the mouth is downturned. The oral commissures are positioned inferior to the midline labial fissure.

Echolalia · Frequent (79-30%)

Echolalia is the automatic imitative repetition of sounds, words, or phrases in the absence of explicit awareness. The repeated words or phrases are typically odd or used in a non-social manner. These can be words or phrases that the affected individual has heard or invented.

Generalized hirsutism · Frequent (79-30%)

Abnormally increased hair growth over much of the entire body.

Hypertelorism · Frequent (79-30%)

Interpupillary distance more than 2 SD above the mean (alternatively, the appearance of an increased interpupillary distance or widely spaced eyes).

Other findings in the same source

From: Orphanet

Additional reported features include Hypointensity of cerebral white matter on MRI (Frequent (79-30%)); Intellectual disability, severe (Frequent (79-30%)); Low posterior hairline (Frequent (79-30%)); Macrocephaly (Frequent (79-30%)); Micropenis (Frequent (79-30%)); Neonatal hyperbilirubinemia (Frequent (79-30%)); Pes cavus (Frequent (79-30%)); Seizure (Frequent (79-30%)); Short foot (Frequent (79-30%)); Synophrys (Frequent (79-30%)). This is a selected summary, not a complete description of the condition.

When it may begin

From: Orphanet

Infancy

Inheritance in the source

From: Orphanet

X-linked recessive

Frequency and the population described

From: Orphanet

Reported case(s): 8.0; Worldwide. This is a published case count, not prevalence. Point prevalence: <1 / 1 000 000; Worldwide; Class only.

Understanding the inheritance label

From: MedlinePlus Genetics

An X-linked recessive pattern involves a gene on the X chromosome. The number of X chromosomes and the particular genetic change influence how a condition is expressed. A genetic counsellor should interpret the result and the family history before discussing risks for relatives or future pregnancies.

Which doctor should you see?

The suggested department for discussing X-linked intellectual disability, Nascimento type 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

The material gathered for this draft does not provide a complete condition-specific treatment pathway for X-linked intellectual disability, Nascimento type. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

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.