Mutations in LAMA1 Cause Cerebellar Dysplasia and Cysts with and without Retinal Dystrophy

Variability of retinopathy consequent upon novel mutations in LAMA1

PURPOSE

Bi-allelic mutations in LAMA1 (laminin 1) (OMIM # 150320) cause Poretti-Boltshauser Syndrome (PTBHS), a rare non-progressive cerebellar dysplasia disorder with ophthalmic manifestations including oculomotor apraxia, high myopia, and retinal dystrophy. Only 38 variants, nearly all loss of function have been reported. Here, we describe novel LAMA1 variants and detailed retinal manifestations in two unrelated families.

METHODS

Whole-genome sequencing was conducted on three siblings of a consanguineous family with myopia and retinal dystrophy and on a child from an unrelated non-consanguineous couple. Clinical evaluation included full ophthalmic examination, detailed colour, autofluorescence retinal imaging, retinal optical coherence tomography (OCT), fluorescein angiography under anesthesia, and pattern and full-field electroretinography.

RESULTS

Genetic analysis revealed a novel homozygous LAMA1 frameshift variant, c.1492del p.(Arg498Glyfs *25), in the affected siblings in family 1 and a novel frameshift c.3065del p.(Gly1022Valfs *2) and a deletion spanning exons 17-23 in an unrelated individual in family 2. Two of the three siblings and the unrelated child had oculomotor apraxia in childhood; none of the siblings had symptoms of other neurological dysfunction as adults. All four had myopia. The affected siblings had a qualitatively similar retinopathy of wide-ranging severity. The unrelated patient had a severe abnormality of retinal vascular development, which resulted in vitreous haemorrhage and neovascular glaucoma in the left eye and a rhegmatogenous retinal detachment in the right eye.

CONCLUSIONS

This report describes the detailed retinal structural and functional consequences of LAMA1 deficiency in four patients from two families, and these exhibit significant variability with evidence of both retinal dystrophy and abnormal and incomplete retinal vascularisation.

Non-invasive prenatal testing detects duplication abnormalities of fetal chromosome 12

PURPOSE

The 12q terminal duplication is a chromosomal structural abnormality that has been rarely reported. The common clinical manifestations include intellectual disability and speech delay. We report two cases of patients with a duplication of chromosome 12q which was discovered incidentally during non-invasive prenatal genetic testing (NIPT).

METHODS

Next generation sequencing-based NIPT and karyotype analysis confirmed the type and inheritance of the rearrangement, and chromosomal microarray-based analysis also confirmed the end replication.

RESULTS

One patient had a 18Mb 12q24.21q24.33 duplication. The other patient had a12.04Mb12.q24.31q24.33 duplication and a 9.56Mb deletion in 18p11.32p11.22. The duplicated regions on chromosome 12 and the deletion on chromosome 18 in the patients were pathogenic, and the fetuses may have clinical characteristics, such as mental retardation, facial deformities, and psychomotor retardation. Ultimately, both pregnant women chose to terminate their pregnancy.

CONCLUSION

The cases we reported show that NIPT cannot only detect conventional chromosomes, but can also detect microdeletions and microduplications, which broadens the scope of clinical application for NIPT and provides genetic information for high-risk pregnant women as early as possible.