PPP2R5D-related intellectual disability

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

PPP2R5D-related intellectual disability is a neurological disorder characterized by moderate to severe developmental delay and intellectual disability. Affected individuals have weak muscle tone (hypotonia); delayed development of motor skills, such as sitting, standing, and walking; and delayed speech development. Recurrent seizures (epilepsy) and autism spectrum disorder, which is characterized by impaired communications and social interaction, can also occur in affected individuals. Most people with PPP2R5D-related intellectual disability have an unusually large head size (macrocephaly), and some have other unusual facial features, including a prominent forehead (frontal bossing), widely spaced eyes (hypertelorism), and eyes that slant downward (downslanting palpebral fissures).

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Mutations in the PPP2R5D gene have been found to cause PPP2R5D-related intellectual disability. This gene provides instructions for making a protein called B56-delta (B56δ). The B56δ protein is one piece of an enzyme called protein phosphatase 2A (PP2A), which removes phosphate groups, consisting of clusters of oxygen and phosphorus atoms, from certain proteins. This process, called dephosphorylation, helps control whether the protein is turned on or off. PP2A enzymes containing the B56δ protein are found mainly in the brain, where they are thought to play roles in the normal development and function of nerve cells (neurons).

PPP2R5D gene mutations are thought to result in the production of an altered B56δ protein. Although the effects of these variations are unclear, researchers suspect that they change or impair the activity of the PP2A enzyme. Abnormal or reduced PP2A enzyme activity is thought to disrupt signaling pathways in neurons, impairing their normal development and functioning, which may underlie intellectual disability and other neurological features of PPP2R5D-related intellectual disability.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.

Most cases of this condition result from new (de novo) mutations in the gene that occur during the formation of reproductive cells (eggs or sperm) in an affected individual’s parent or in early embryonic development. These cases occur in people with no history of the disorder in their family.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

PPP2R5D-related intellectual disability is a rare disorder. At least 20 individuals with this condition have been described in the medical literature.

Understanding terms used in the source

These definitions explain medical words used above. A definition is not evidence that another condition is present, and it does not predict how a symptom will develop. Ask the clinician which terms apply to the actual examination or test result.

Intellectual disability

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.

Prominent forehead

Forward prominence of the entire forehead, due to protrusion of the frontal bone.

Frontal bossing

Bilateral bulging of the lateral frontal bone prominences with relative sparing of the midline.

Hypertelorism

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

Macrocephaly

Occipitofrontal (head) circumference greater than 97th centile compared to appropriate, age matched, sex-matched normal standards. Alternatively, a apparently increased size of the cranium.

Which doctor should you see?

The suggested department for discussing PPP2R5D-related intellectual disability 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 PPP2R5D-related intellectual disability. 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.