Multimodal retinal imaging in MFSD8-neuronal ceroid lipofuscinosis

Simultaneous Identification of Both MFSD8 and RDH12 Pathogenic Variants in a Chinese Family Affected With Retinitis Pigmentosa

Retinitis pigmentosa (RP) is characterized by tremendous genetic and phenotypic heterogeneity. Here, we investigate the pathogeny of RP in a family to provide evidence for genetic and reproductive counseling for families. Although this pregnant woman of 8⁺³ weeks presented with RP, her first baby was born with RP, epilepsy, and cerebellar atrophy. The research identified a compound heterozygous mutation (c.998+3_998+6del/deletion) in the MFSD8 gene of the first born, explaining the cause of the proband’s disease, which cannot explain the mother’s. Then, a homozygous mutation c.343+1G > A in RDH12 of the mother was found. RT-PCR is employed to find that there is a skipping of exon 10 in MFSD8 and a 15-nucleotide retention of intron5 in RDH12. The coexistence of two independent instances of RP caused by distinct genes in one pedigree is demonstrated. Based on the diagnosis, a prenatal diagnosis performed on the fetus found that the fetus’s MFSD8 is affected by the same mutation as the proband. The research underscoring the complexity of RP and the need for the combination of extensive molecular genetic testing and clinical characterization in addition expands the spectrum of MFSD8 mutations. Finally, it is expected that the family members would be prevented from reproducing children with the similar disease.

Association of the Recurrent Rare Variant c.415T>C p.Phe139Leu in CLN5 With a Recessively Inherited Macular Dystrophy

Importance

Homozygous variants in the neuronal ceroid lipofuscinosis type 5 (CLN5) gene are associated with neuronal ceroid lipofuscinosis, a progressive neurologic disorder that leads to ataxia, seizures, and early death. The association between a homozygous variant in this gene and a macular dystrophy is described here.

Objective

To describe an autosomal recessive macular dystrophy associated with a recurrent variant in CLN5.

Design, Setting, and Participants

This cohort study took place at a national referral center and had a follow-up duration ranging between 1 and 5 years. All patients who were identified to carry a specific homozygous missense variant in CLN5, among more than 2000 patients who were diagnosed with or suspected to have retinal dystrophies, who did not carry this variant, were included. Data were collected between June 2014 and September 2020.

Exposures

All patients who were sampled for DNA analysis due to molecularly unconfirmed retinal dystrophy and who were subsequently identified to carry the homozygous missense variant c.415T>C (p.Phe139Leu) in CLN5 were included, while patients who did not carry the variant were excluded.

Main Outcomes and Measures

Retinal phenotype associated with this specific homozygous missense variant in CLN5.

Results

Seven affected patients (mean [SD] age, 43 [18] years; age range, 33-52 years; 5 male) carried the homozygous missense in CLN5. All patients were diagnosed as having a macular dystrophy. Four patients had mild electroretinographic alterations. All patients had hypoautofluorescent maculas with retinal thinning (central subfield thickness, 80 µm). Visual acuity ranged between 2/200 and 20/100. Neurologic symptoms were mild (dizziness) in 5 patients and absent in 2 patients. Neuroimaging demonstrated cerebellar atrophy and white matter lesions, respectively, in 2 patients.

Conclusions and Relevance

These results suggest that CLN5, similar to CLN7, may be associated with isolated macular dystrophy as well as neuronal ceroid lipofuscinosis. The variant c.415T>C p.Phe139Leu does not seem to be associated with any prominent neurologic disease at least until the fourth to sixth decades of life. These findings may imply a specific role of CLN5 in macular neurons. Additional study is suggested, such as molecular screening for this variant in cohorts of patients with undiagnosed macular dystrophies and biological studies of its molecular effects.