SLC39A8-CDG

What it is

From: Orphanet

A rare congenital disorder of glycosylation characterized by infantile onset of global developmental delay, severe intellectual disability, hypotonia, and variable additional features including short stature, cranial asymmetry, seizures, strabismus, recurrent infections, and osteopenia, among others. Laboratory analysis reveals decreased blood levels of zinc and manganese, as well as an abnormal serum transferrin glycosylation pattern with decreased tetrasialo- and increased asialo-, monosialo-, disialo, and trisialo-transferrin, consistent with a type II congenital disorder of glycosylation. Brain imaging shows cerebellar and/or cerebral atrophy.

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 zinc homeostasis · Very frequent (99-80%)

Any deviation from the normal concentration of zinc in the blood circulation.

Hypomanganesemia · Very frequent (99-80%)

The concentration of manganese cation in the blood circulation is below the lower limit of normal.

Intellectual disability, profound · Very frequent (99-80%)

Profound intellectual disability (ID) is defined as a type of ID characterized by profoundly sub-average adaptive functioning and intellectual functioning, with an intelligence quotient (IQ) below 20.

Profound global developmental delay · Very frequent (99-80%)

A profound delay in the achievement of motor or mental milestones in the domains of development of a child.

Severe muscular hypotonia · Very frequent (99-80%)

A severe degree of muscular hypotonia characterized by markedly reduced muscle tone.

Type II transferrin isoform profile · Very frequent (99-80%)

Abnormal transferrin isoform profile consistent with a type II congenital disorder of glycosylation.

Cerebellar atrophy · Frequent (79-30%)

Cerebellar atrophy is defined as a cerebellum with initially normal structures, in a posterior fossa with normal size, which displays enlarged fissures (interfolial spaces) in comparison to the foliae secondary to loss of tissue. Cerebellar atrophy implies irreversible loss of tissue and result from an ongoing progressive disease until a final stage is reached or a single injury, e.g. an intoxication or infectious event.

Cerebral cortical atrophy · Frequent (79-30%)

Atrophy of the cortex of the cerebrum.

Inability to walk · Frequent (79-30%)

Incapability to ambulate.

Poor head control · Frequent (79-30%)

Difficulty to maintain correct position of the head while standing or sitting. Infant head lag is observed when the head seems to flop around or lags posteriorly behind the trunk. Several articles have maintained that head lag should be absent by age 3 to 4 months.

Seizure · Frequent (79-30%)

A seizure is an intermittent abnormality of nervous system physiology characterized by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.

Short stature · Frequent (79-30%)

A height below that which is expected according to age and gender norms. Although there is no universally accepted definition of short stature, many refer to "short stature" as height more than 2 standard deviations below the mean for age and gender (or below the 3rd percentile for age and gender dependent norms).

Strabismus · Frequent (79-30%)

A misalignment of the eyes so that the visual axes deviate from bifoveal fixation. The classification of strabismus may be based on a number of features including the relative position of the eyes, whether the deviation is latent or manifest, intermittent or constant, concomitant or otherwise and according to the age of onset and the relevance of any associated refractive error.

Visual fixation instability · Frequent (79-30%)

A deficit in the ability to fixate eye movements in order to stabilize images on the retina

Other findings in the same source

From: Orphanet

Additional reported features include Failure to thrive in infancy (Frequent (79-30%)); Abnormality of the liver (Occasional (29-5%)); Astigmatism (Occasional (29-5%)); Craniosynostosis (Occasional (29-5%)); Cutaneous syndactyly of toes (Occasional (29-5%)); Decreased activity of mitochondrial complex II (Occasional (29-5%)); Decreased activity of mitochondrial complex IV (Occasional (29-5%)); Decreased mitochondrial complex III activity in liver tissue (Occasional (29-5%)); Disproportionate short-limb short stature (Occasional (29-5%)); Dystonia (Occasional (29-5%)). This is a selected summary, not a complete description of the condition.

When it may begin

From: Orphanet

Neonatal

Inheritance in the source

From: Orphanet

Autosomal recessive

Frequency and the population described

From: Orphanet

Reported case(s): 10.0; 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 autosomal recessive pattern usually involves disease-causing changes in both copies of a gene. Parents may each carry one altered copy without having the condition themselves. A genetic counsellor can explain carrier testing and reproductive implications using the actual laboratory findings, rather than the condition name alone.

Which doctor should you see?

The suggested department for discussing SLC39A8-CDG is Metabolic Medicine, with a metabolic specialist / clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with metabolic specialist / 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.

• Is a biochemical or molecular result needed to clarify the diagnosis?
• Does this condition require an individual plan for illness or reduced food intake?
• Should nutrition advice come from a specialist metabolic dietitian?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for SLC39A8-CDG. 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.