CLN2 disease

CLN2 disease is a neuronal ceroid lipofuscinosis caused by deficient tripeptidyl peptidase 1 (TPP1) activity from biallelic pathogenic variants in TPP1. It is a progressive lysosomal neurodegenerative disorder. The classic late-infantile phenotype often begins with slowing language development and seizures, followed by changes in movement, cognition, vision, and swallowing. Atypical forms can begin later and progress more slowly.1

Urgent safety

Follow the person's seizure action plan. Call emergency services for a seizure that reaches the plan's emergency threshold, repeated seizures without recovery, breathing difficulty or color change, serious injury, or a first or substantially changed seizure. Do not give extra rescue medicine outside the prescribed plan.2

Seek urgent assessment for choking, inability to clear secretions, marked dehydration, acute loss of alertness, or a rapid change in movement or function.

People receiving cerliponase alfa have an implanted intraventricular access device and a treatment-center safety plan. Fever, significant headache or vomiting, redness, swelling or leakage over the device, a device problem, or an infusion reaction needs immediate contact with the treatment team; breathing difficulty or signs of anaphylaxis require emergency care.3

Phenotypes and diagnosis

The classic late-infantile pattern often includes:

• slowing or loss of language and other developmental skills;
• epilepsy with more than one seizure type;
• ataxia, myoclonus, dystonia, and later loss of mobility;
• progressive visual impairment;
• sleep, behavior, swallowing, respiratory, and gastrointestinal concerns.

Atypical TPP1-related disease may begin from preschool age through adulthood with seizures, ataxia, cerebellar atrophy, vision change, or other neurologic findings. Age at onset and progression cannot be inferred from the label alone.1

Diagnosis is established through molecular testing that identifies biallelic pathogenic or likely pathogenic TPP1 variants, with deficient TPP1 enzyme activity used to support or clarify the result. A variant of uncertain significance does not establish the diagnosis. MRI, EEG, eye examination, and developmental assessment characterize current involvement but are not substitutes for etiologic testing.1

CLN2 disease is autosomal recessive. Family testing, recurrence counseling, and reproductive options should use the confirmed variants with a genetics professional.1

Disease-modifying and supportive care

Cerliponase alfa is an intracerebroventricular enzyme-replacement therapy approved by the FDA to slow loss of ambulation in pediatric patients with CLN2 disease. It is not a cure, does not restore all lost function, and does not prevent every manifestation. Treatment requires specialist selection, a surgically implanted access device, scheduled infusions, and device, infection, and hypersensitivity monitoring.13

Because benefit depends on timely diagnosis and treatment context, suspected CLN2 disease warrants prompt referral to an experienced center. Seizure, vision, movement, sleep, pain, nutrition, respiratory, orthopedic, dental, rehabilitation, and palliative care remain important whether or not enzyme replacement is used. Medication, equipment, exercise, positioning, and nutrition plans should respond to current function and goals.

Swallowing and communication

Swallowing review should consider coughing or choking, wet or changed voice, respiratory symptoms, prolonged meals, fatigue, weight and hydration, saliva management, vision, posture, and motor control. Texture, pacing, positioning, equipment, and tube-feeding decisions require direct assessment.1

Communication access should be planned early and revised as language, motor control, vision, seizures, and fatigue change. Preserve established vocabulary, relationships, preferences, and participation in decisions. Loss of speech or vision does not erase intent or the right to be addressed directly.

AAC may combine gesture, objects or tactile cues, auditory scanning, pictures while visually accessible, stored messages, switches, partner-assisted scanning, and speech-generating systems. Do not prescribe eye gaze, touch, symbols, or a switch from the diagnosis. Trial access in real positions and activities, include urgent and personally meaningful messages, train partners, and maintain a low-tech or no-tech backup.4 For evaluation, trials, funding, and implementation, use the AAC device acquisition guide.

Coding

• ICD-10-CM E75.4: Neuronal ceroid lipofuscinosis.

This is a broad NCL descriptor, not specific to CLN2 or TPP1. Preserve the molecular diagnosis and associated conditions in the clinical record and follow current local coding rules.5

Sources

1. Malik et al. Neuronal Ceroid Lipofuscinoses Overview, GeneReviews — current CLN2 phenotype, diagnosis, inheritance, and targeted-therapy context.
2. Mole et al. Guidelines on diagnosis, assessment, treatment, and management for CLN2 disease — international condition-specific consensus guidance (2021; PMID 33882967).
3. US Food and Drug Administration: Brineura prescribing information — current pediatric indication, intraventricular administration, device, infection, and hypersensitivity warnings.
4. American Speech-Language-Hearing Association: Augmentative and Alternative Communication — individualized, multimodal AAC assessment.
5. Centers for Medicare & Medicaid Services: FY2026 ICD-10-CM definitions — E75.4 descriptor.

Review boundary

This page cannot diagnose CLN2 disease or remotely assess seizures, swallowing, respiratory risk, an implanted access device, or infusion reactions. Emergencies require immediate local assessment. Enzyme replacement, rescue medication, surgery, other treatment, diet, equipment, mobility, and communication decisions require direct review by qualified clinicians with the person and family.