Autosomal recessive spastic paraplegia type 55

What it is

From: Orphanet

Autosomal recessive spastic paraplegia type 55 (SPG 55) is a rare, complex type of hereditary spastic paraplegia characterized by childhood onset of progressive spastic paraplegia associated with optic atrophy (with reduced visual acuity and central scotoma), ophthalmoplegia, reduced upper-extremity strength and dexterity, muscular atrophy in the lower extremities, and sensorimotor neuropathy. SPG55 is caused by mutations in the C12ORF65 gene (12q24.31) encoding probable peptide chain release factor C12orf65, mitochondrial.

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.

Babinski sign · Frequent (79-30%)

Upturning of the big toe (and sometimes fanning of the other toes) in response to stimulation of the sole of the foot. If the Babinski sign is present it can indicate damage to the corticospinal tract.

Decreased sensory nerve conduction velocity · Frequent (79-30%)

Reduced speed of conduction of the action potential along a sensory nerve.

Distal sensory impairment · Frequent (79-30%)

An abnormal reduction in sensation in the distal portions of the extremities.

Foot dorsiflexor weakness · Frequent (79-30%)

Weakness of the muscles responsible for dorsiflexion of the foot, that is, of the movement of the toes towards the shin. The foot dorsiflexors include the tibialis anterior, the extensor hallucis longus, the extensor digitorum longus, and the peroneus tertius muscles.

Hyperreflexia · Frequent (79-30%)

Hyperreflexia is the presence of hyperactive stretch reflexes of the muscles.

Hypoplasia of the corpus callosum · Frequent (79-30%)

Underdevelopment of the corpus callosum.

Intellectual disability, mild · Frequent (79-30%)

Mild intellectual disability (ID) is defined as a type of ID characterized by mildly sub-average adaptive functioning and intellectual functioning, with an intelligence quotient (IQ) the range of 50-69.

Lower limb muscle weakness · Frequent (79-30%)

Weakness of the muscles of the legs.

Lower limb spasticity · Frequent (79-30%)

Spasticity (velocity-dependent increase in tonic stretch reflexes with increased muscle tone and hyperexcitable tendon reflexes) in the muscles of the lower limbs, hips, and pelvis.

Onion bulb formation · Frequent (79-30%)

Repeated episodes of segmental demyelination and remyelination lead to the accumulation of supernumerary Schwann cells around axons, which is referred to as onion bulb formation. This finding affects peripheral nerves.

Optic atrophy · Frequent (79-30%)

Atrophy of the optic nerve. Optic atrophy results from the death of the retinal ganglion cell axons that comprise the optic nerve and manifesting as a pale optic nerve on fundoscopy.

Peripheral neuropathy · Frequent (79-30%)

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.

Poor fine motor coordination · Frequent (79-30%)

An abnormality of the ability (skills) to perform a precise movement of small muscles with the intent to perform a specific act. Fine motor skills are required to mediate movements of the wrists, hands, fingers, feet, and toes.

Skeletal muscle atrophy · Frequent (79-30%)

The presence of skeletal muscular atrophy (which is also known as amyotrophy).

Other findings in the same source

From: Orphanet

Additional reported features include Spastic paraparesis (Frequent (79-30%)); Spasticity (Frequent (79-30%)); Talipes equinovarus (Frequent (79-30%)); Tibialis muscle weakness (Frequent (79-30%)); Upper limb muscle weakness (Frequent (79-30%)); Focal white matter lesions (Frequent (79-30%)); Optic neuropathy (Frequent (79-30%)); Reduced visual acuity (Frequent (79-30%)); Abnormal facial shape (Occasional (29-5%)); Arthrogryposis multiplex congenita (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

Frequency and the population described

From: Orphanet

Point prevalence: <1 / 1 000 000; Worldwide; Class only. Reported case(s): 14.0; Worldwide. This is a published case count, not prevalence.

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 spastic paraplegia type 55 is Neurology, with a neurologist 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 nervous-system findings help explain the symptoms?
• Would an assessment of walking, communication or daily function be helpful?
• Are rehabilitation or other specialist services relevant?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Autosomal recessive spastic paraplegia type 55. 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.