Autosomal recessive methemoglobinemia

What it is

From: Orphanet

A rare red cell disorder classified principally into two clinical phenotypes: autosomal recessive congenital (or hereditary) methemoglobinemia types I and II (RCM/RHM type 1; RCM/RHM type 2).

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.

Cyanosis · Very frequent (99-80%)

Bluish discoloration of the skin and mucosa due to poor circulation or inadequate oxygenation of arterial or capillary blood.

Methemoglobinemia · Very frequent (99-80%)

Abnormally increased levels of methemoglobin in the blood. In this form of hemoglobin, there is an oxidized ferric iron (Fe +3) rather than the reduced ferrous form (Fe 2+) that is normally found in hemoglobin. Methemoglobin has a reduced affinity for oxygen, resulting in a reduced ability to release oxygen to tissues.

Abnormal nail morphology · Frequent (79-30%)

Abnormal structure or appearance of the nail.

Abnormality of the nervous system · Frequent (79-30%)

An abnormality of the nervous system.

Exertional dyspnea · Frequent (79-30%)

Perceived difficulty to breathe that occurs with exercise or exertion and improves with rest.

Lip discoloration · Frequent (79-30%)

Lightening or darkening of the lips from their usual coloring.

Athetosis · Occasional (29-5%)

A slow, continuous, involuntary writhing movement that prevents maintenance of a stable posture. Athetosis involves continuous smooth movements that appear random and are not composed of recognizable sub-movements or movement fragments. In contrast to chorea, in athetosis, the same regions of the body are repeatedly involved. Athetosis may worsen with attempts at movement of posture, but athetosis can also occur at rest.

Blue sclerae · Occasional (29-5%)

An abnormal bluish coloration of the sclera.

Cerebellar atrophy · Occasional (29-5%)

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 hypomyelination · Occasional (29-5%)

Reduced amount of myelin in the nervous system resulting from defective myelinogenesis in the white matter of the central nervous system.

Esotropia · Occasional (29-5%)

A form of strabismus with one or both eyes turned inward ('crossed') to a relatively severe degree, usually defined as 10 diopters or more.

Frontal cortical atrophy · Occasional (29-5%)

Atrophy of the frontal cortex.

Global brain atrophy · Occasional (29-5%)

Unlocalized atrophy of the brain with decreased total brain matter volume and increased ventricular size.

Global developmental delay · Occasional (29-5%)

A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age.

Other findings in the same source

From: Orphanet

Additional reported features include Intellectual disability, severe (Occasional (29-5%)); Limb dystonia (Occasional (29-5%)); Microcephaly (Occasional (29-5%)); Severe global developmental delay (Occasional (29-5%)); Spastic tetraplegia (Occasional (29-5%)); Spasticity (Occasional (29-5%)); Temporal cortical atrophy (Occasional (29-5%)); Delayed myelination (Very rare (<4-1%)); Hypertonia (Very rare (<4-1%)); Seizure (Very rare (<4-1%)). 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

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 Autosomal recessive methemoglobinemia 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 Autosomal recessive methemoglobinemia. 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.