Chronic neurovisceral acid sphingomyelinase deficiency

What it is

From: Orphanet

A rare acid sphingomyelinase deficiency characterized by mild to massive hepatosplenomegaly, hypersplenism leading to thrombocytopenia, interstitial lung disease, dyslipidemia and central nervous system manifestations (including developmental delay, intellectual disability and ataxia). Some affected individuals may present with coarse facial features.

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.

Abnormal pulmonary interstitial morphology · Very frequent (99-80%)

Abnormality of the lung parenchyma extending to the pulmonary interstitium and leading to diffuse pulmonary fibrosis.

Decreased acid sphingomyelinase activity · Very frequent (99-80%)

Reduced activity of the enzyme acid sphingomyelinase activity in the blood circulation.

Hepatosplenomegaly · Very frequent (99-80%)

Simultaneous enlargement of the liver and spleen.

Hypersplenism · Very frequent (99-80%)

A malfunctioning of the spleen in which it prematurely destroys red blood cells.

Hepatic failure · Very frequent (99-80%)

Abdominal distention · Frequent (79-30%)

Distention of the abdomen.

Anemia · Frequent (79-30%)

A reduction in erythrocytes volume or hemoglobin concentration.

Ataxia · Frequent (79-30%)

Ataxia refers to impaired coordination of voluntary muscle movement. Cerebellar ataxia refers to ataxia due to dysfunction of the cerebellum. This causes a variety of elementary neurological deficits including asynergy (lack of coordination between muscles, limbs and joints), dysmetria (lack of ability to judge distances that can lead to under- or overshoot in grasping movements), and dysdiadochokinesia (inability to perform rapid movements requiring antagonizing muscle groups to be switched on and off repeatedly).

Cherry red spot of the macula · Frequent (79-30%)

Pallor of the perifoveal macula of the retina with appearance of a small circular reddish choroid shape as seen through the fovea centralis due to relative transparency of the macula.

Delayed skeletal maturation · Frequent (79-30%)

A decreased rate of skeletal maturation. Delayed skeletal maturation can be diagnosed on the basis of an estimation of the bone age from radiographs of specific bones in the human body.

Elevated circulating hepatic transaminase concentration · Frequent (79-30%)

Elevations of the levels of SGOT and SGPT in the serum. SGOT (serum glutamic oxaloacetic transaminase) and SGPT (serum glutamic pyruvic transaminase) are transaminases primarily found in the liver and heart and are released into the bloodstream as the result of liver or heart damage. SGOT and SGPT are used clinically mainly as markers of liver damage.

Growth delay · Frequent (79-30%)

A deficiency or slowing down of growth pre- and postnatally.

Mental deterioration · Frequent (79-30%)

Loss of previously present mental abilities, generally in adults.

Recurrent pneumonia · Frequent (79-30%)

An increased susceptibility to pneumonia as manifested by a history of recurrent episodes of pneumonia.

Other findings in the same source

From: Orphanet

Additional reported features include Thrombocytopenia (Frequent (79-30%)); Abdominal pain (Occasional (29-5%)); Abnormality of extrapyramidal motor function (Occasional (29-5%)); Ascites (Occasional (29-5%)); Coarse facial features (Occasional (29-5%)); Decreased HDL cholesterol concentration (Occasional (29-5%)); Dementia (Occasional (29-5%)); Depressed nasal bridge (Occasional (29-5%)); Failure to thrive (Occasional (29-5%)); Hepatic fibrosis (Occasional (29-5%)). This is a selected summary, not a complete description of the condition.

When it may begin

From: Orphanet

Infancy; Neonatal

Inheritance in the source

From: Orphanet

Autosomal recessive

Frequency and the population described

From: Orphanet

Point prevalence: Unknown; 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 Chronic neurovisceral acid sphingomyelinase deficiency 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 Chronic neurovisceral acid sphingomyelinase deficiency. 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.