A number sign (#) is used with this entry because of evidence that neuronal ceroid lipofuscinosis-11 (CLN11) is caused by homozygous mutation in the GRN gene (138945) on chromosome 17q.

Heterozygous and, rarely, biallelic mutation in the GRN gene causes frontotemporal dementia-2 (FTD2; 607485).

Neuronal ceroid lipofuscinosis-11 (CLN11) is an autosomal recessive progressive neurodegenerative disorder characterized by seizures (often refractory), progressive cerebellar ataxia and gait abnormalities, cognitive decline particularly affecting executive function, and behavioral abnormalities. The age at onset is variable, ranging from midchildhood to the second or third decades. Most patients have progressive visual loss with retinal abnormalities and cataracts; visual hallucinations may occur and many patients are photosensitive. The severity of the disorder is variable, but it is progressive and can lead to severe disability with blindness, loss of ambulation, and severe cognitive impairment (Huin et al., 2020; Neuray et al., 2021).

For a general phenotypic description and a discussion of genetic heterogeneity of CLN, see CLN1 (256730).

Smith et al. (2012) reported 2 Italian sibs with young-adult onset of neuronal ceroid lipofuscinosis. Their healthy parents, who were in their fifties, came from nearby villages in Lombardy, Italy, and were demonstrated to be distantly related. The proband was a 28-year-old man who presented with rapidly progressive visual failure at age 22, followed by major convulsions at age 25 and myoclonic seizures at age 26. He had mild cerebellar ataxia, early cognitive deterioration, and retinal dystrophy. Electroencephalogram (EEG) showed generalized polyspike wave discharges, electroretinogram showed severe attenuation of both rod and cone responses, and MRI showed cerebellar atrophy. Electron microscopic examination of a skin biopsy demonstrated numerous fingerprint profiles in membrane-bound structures in eccrine secretory cells and in endothelium, consistent with CLN. The proband's 26-year-old sister developed recurrent seizures at age 23 years, sometimes preceded by visual distortions, and she later had visual deterioration. Clinical examination showed cerebellar ataxia and retinal dystrophy. EEG results showed polyspike wave discharges with a posterior emphasis, and MRI indicated cerebellar atrophy.

Canafoglia et al. (2014) reported follow-up of the Italian sibs reported by Smith et al. (2012). Both showed increasing visual impairment and developed retinal changes. Both also had palinopsia associated with polyphasic visual evoked potential (VEP) waveforms, suggesting hyperexcitability of the occipital cortex. Detailed ophthalmologic studies in the brother showed retinal pigment epithelial dystrophy and stippling, thinning of the retina, and optic nerve pallor. VEPs showed depressed cortical components and virtually absent electroretinographic responses in both patients. Brain imaging in both sibs showed progressive cerebellar atrophy. Global cognition in both sibs was normal with borderline executive functions; both were able to work despite severe visual impairment. Plasma and tissue levels of GRN were undetectable.

Faber et al. (2017) reported 25-year-old woman, born of possibly related Brazilian parents, who presented with a 4-year history of progressive gait impairment and urinary incontinence. She also developed mood lability, delusional thoughts, and photosensitive seizures. Physical exam showed high-arched feet, appendicular ataxia, lower limb spasticity, hyperreflexia, and extensor plantar responses, suggesting a form of complicated spastic paraplegia. Her gait was both spastic and wide-based. Brain MRI showed global and severe cerebellar atrophy. EEG showed slow wave background activity and epileptiform discharges predominating in posterior regions during photostimulation. Her executive function and cognition continued to decline, and walking was possible only with support. Ophthalmologic examination was not possible due to poor cooperation. Her parents, who were in their fifties, were asymptomatic. Genetic analysis identified a homozygous frameshift mutation in the GRN gene. Familial segregation studies could not be performed and functional studies of the variant and studies of patient cells were not performed.

Kamate et al. (2019) reported a 14-year-old girl, born of consanguineous Indian parents, who presented with a 1-year history of seizures. There were no visual disturbances or decline in school performance. Physical examination showed a wide-based gait and borderline intelligence. EEG showed generalized epileptiform discharges, and brain imaging showed diffuse cerebellar atrophy and hypoplasia. She had an elder sister with progressive seizures and dementia from 8 years of age and cerebellar atrophy on brain imaging, who had died at age 16 years.

Huin et al. (2020) reported 3 patients from 2 unrelated families with CLN11. Two sisters, born of possibly consanguineous Portuguese parents (family AAR-427), presented with seizures between 12 and 15 years of age. They soon developed progressive visual loss associated with retinitis pigmentosa and bilateral cataracts, as well as behavioral abnormalities, including irritability and impulsiveness, and cognitive deficits affecting executive function. Additional features included a cerebellar gait disorder with dysarthria, saccadic pursuit, nystagmus, and dysphagia, myoclonus, and visual hallucinations. Brain imaging showed progressive cerebellar atrophy. The proband died at age 27 from food inhalation during an epileptic seizure. At age 36, the sister was blind with dysarthria and dysphagia and needed a wheelchair. Peripheral lymphocytes contained vacuolar inclusions, and plasma progranulin levels were undetectable. Neuropathologic examination of the proband showed cerebellar atrophy, ballooned neurons, neuronal loss, and diffuse cytoplasmic expression of TDP43 (605078). Ultrastructural analysis of temporal cortex neurons showed numerous lysosomal deposits with curvilinear-like profiles and few fingerprint profiles, suggesting lysosomal dysfunction. The parents were asymptomatic at 57 and 61 years of age, and had low levels of plasma progranulin. An unrelated girl, born of consanguineous Pakistani parents (family NCL-001), presented with seizures at 7 years of age, followed by by progressive cerebellar ataxia with cerebellar atrophy on MRI, cognitive deterioration, and visual loss. Skin biopsy showed vesicles filled with curvilinear membrane formations. Plasma progranulin was undetectable. The parents were unaffected at 46 and 47 years of age.

Neuray et al. (2021) reported 6 patients with CLN11 from 5 unrelated families, 4 of which were consanguineous (Pakistani, Italian, Kurdish, and Brazilian). The patients, who ranged from 10 to 40 years of age, had symptom onset between 5 and 15 years of age. Features included seizures (usually difficult to treat), progressive visual loss (leading to blindness in some cases), progressive ataxia (sometimes with loss of ambulation), and progressive cognitive decline of executive and memory functions, resulting in poor school performance. EEG showed generalized spikes as well as occipital spikes elicited by photostimulation. Brain imaging showed cerebellar atrophy. More variable features included nystagmus, retinitis pigmentosa, dysphagia, dysarthria, dysmetria, and tremor. Progranulin levels were undetectable in the 1 patient who was tested. All carrier parents, who ranged from 36 to 72 years of age, were healthy and unaffected, although the authors noted some may have been too young to manifest symptoms.

The transmission pattern of CLN11 in the family reported by Smith et al. (2012) was consistent with autosomal recessive inheritance.

By exome sequencing of 2 Italian sibs with young-adult onset of CLN, Smith et al. (2012) identified a homozygous 4-bp deletion in the GRN gene (138945.0015). Heterozygosity for this mutation had previously been identified in patients with late-onset frontotemporal dementia (607485). Plasma progranulin levels in the homozygous patients were undetectable and were about 50% decreased in the heterozygous parents. Family history revealed 3 cases of late-onset dementia in both sides of the family, but DNA was not available from these patients. The healthy parents were in their fifties; the molecular findings suggested that they may be at risk for later-onset dementia. Smith et al. (2012) commented on the remarkable phenotypic differences between heterozygous and homozygous GRN mutations, and suggested that progranulin may have a lysosomal function.

In a 14-year-old Indian girl, born of consanguineous parents, with CLN11, Kamate et al. (2019) identified a homozygous nonsense mutation in the GRN gene (W304X; 138945.0020). The mutation, which was found by next-generation sequencing and confirmed by Sanger sequencing, was present in the heterozygous state in each unaffected parent and an unaffected sib. Functional studies of the variant and studies of patient cells were not performed, but the mutation was predicted to result in a complete loss of GRN. Serum GRN levels were not assessed.

In 3 patients from 2 unrelated families with CLN11, Huin et al. (2020) identified homozygous mutations in the GRN gene: a frameshift (138945.0021) and a mutation affecting the initiation codon (Met1?; 138945.0022). The mutations, which were found by exome sequencing or molecular screening of a CLN panel and confirmed by Sanger sequencing, segregated with the disorder in both families. Functional studies of the mutations were not performed, but plasma progranulin was undetectable in the patients, suggesting a complete loss of function. The authors noted that both mutations had been detected in the heterozygous state in patients with FTD2 (607485).

In 6 patients from 5 unrelated families with CLN11, Neuray et al. (2021) identified homozygous putative loss-of-function mutations in the GRN gene (R493X, 138945.0009; c.813delCACT, 138945.0015; and c.768dupCC; 138945.0021). One of the mutations was a deletion of the entire GRN coding sequence. Functional studies of the variants were not performed. Of note, some of these mutations caused FTD in the heterozygous state. However, all of the carrier parents, who ranged from 36 to 72 years of age, were healthy and unaffected, although the authors noted some may have been too young to manifest dementia.

Ahmed et al. (2010) found that Grn-null mice developed abnormal accumulation of abnormal intraneuronal ubiquitin-positive autofluorescent lipofuscin detected by light microscopy. Electron microscopic examination of fixed brain tissue from Grn-null showed abundant rectilinear profiles diagnostic of CLN (Smith et al., 2012).