Congenital intrinsic factor deficiency

What it is

From: Orphanet

Congenital intrinsic factor deficiency (IFD) is a rare disorder of vitamin B12 (cobalamin) absorption that is characterized by megaloblastic anemia and neurological abnormalities.

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.

Absence of intrinsic factor · Obligate (100%)

Absence of gastric intrinsic factor, which is normally produced by the parietal cells of the stomach, and is required for the absorption of vitamin B12.

Decreased circulating vitamin B12 concentration · Very frequent (99-80%)

The concentration of vitamin B12 in the blood circulation is below the lower limit of normal.

Megaloblastic anemia · Very frequent (99-80%)

Anemia characterized by the presence of erythroblasts that are larger than normal (megaloblasts).

Asthenia · Frequent (79-30%)

A state characterized by a feeling of weakness and loss of strength leading to a generalized weakness of the body.

Dementia · Frequent (79-30%)

A loss of global cognitive ability of sufficient amount to interfere with normal social or occupational function. Dementia represents a loss of previously present cognitive abilities, generally in adults, and can affect memory, thinking, language, judgment, and behavior.

Hyperhomocystinemia · Frequent (79-30%)

The concentration of homocystine in the blood circulation is above the upper limit of normal.

Methylmalonic acidemia · Frequent (79-30%)

The concentration of methylmalonic acid in the blood circulation is above the upper limit of normal.

Recurrent infections · Frequent (79-30%)

Increased susceptibility to infections as manifested by repeated bouts of infection.

Specific learning disability · Frequent (79-30%)

Impairment of certain skills such as reading or writing, coordination, self-control, or attention that interfere with the ability to learn. The impairment is not related to a global deficiency of intelligence.

Growth delay · Occasional (29-5%)

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

Headache · Occasional (29-5%)

Cephalgia, or pain sensed in various parts of the head, not confined to the area of distribution of any nerve.

Methylmalonic aciduria · Occasional (29-5%)

Increased concentration of methylmalonic acid in the urine.

Paresthesia · Occasional (29-5%)

Abnormal sensations such as tingling, pricking, or numbness of the skin with no apparent physical cause.

Peripheral neuropathy · Occasional (29-5%)

Peripheral neuropathy is a general term for any disorder of the peripheral nervous system. The main clinical features used to classify peripheral neuropathy are distribution, type (mainly demyelinating versus mainly axonal), duration, and course.

Other findings in the same source

From: Orphanet

Additional reported features include Atrophy of the spinal cord (Occasional (29-5%)); Megaloblastic erythroid hyperplasia (Occasional (29-5%)). This is a selected summary, not a complete description of the condition.

When it may begin

From: Orphanet

Childhood

Inheritance in the source

From: Orphanet

Autosomal recessive; Not applicable

Frequency and the population described

From: Orphanet

Reported case(s): 100.0; Worldwide. This is a published case count, not prevalence. Point prevalence: <1 / 1 000 000; Worldwide; Class only.

Which doctor should you see?

The suggested department for discussing Congenital intrinsic factor deficiency is Haematology, with a haematologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

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.

• Which blood-cell, marrow, bleeding or clotting finding matters most?
• Does the diagnosis need confirmation or a more precise subtype?
• Which symptoms or laboratory changes should trigger earlier review?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Congenital intrinsic factor 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.