Diagnosing Sjögren-Larsson syndrome in a 7-year-old Moroccan boy

Clinical and genetic spectrums of 413 North African families with inherited retinal dystrophies and optic neuropathies

Background

Inherited retinal dystrophies (IRD) and optic neuropathies (ION) are the two major causes world-wide of early visual impairment, frequently leading to legal blindness. These two groups of pathologies are highly heterogeneous and require combined clinical and molecular diagnoses to be securely identified. Exact epidemiological studies are lacking in North Africa, and genetic studies of IRD and ION individuals are often limited to case reports or to some families that migrated to the rest of the world. In order to improve the knowledge of their clinical and genetic spectrums in North Africa, we reviewed published data, to illustrate the most prevalent pathologies, genes and mutations encountered in this geographical region, extending from Morocco to Egypt, comprising 200 million inhabitants.

Main body

We compiled data from 413 families with IRD or ION together with their available molecular diagnosis. The proportion of IRD represents 82.8% of index cases, while ION accounted for 17.8%. Non-syndromic IRD were more frequent than syndromic ones, with photoreceptor alterations being the main cause of non-syndromic IRD, represented by retinitis pigmentosa, Leber congenital amaurosis, and cone-rod dystrophies, while ciliopathies constitute the major part of syndromic-IRD, in which the Usher and Bardet Biedl syndromes occupy 41.2% and 31.1%, respectively. We identified 71 ION families, 84.5% with a syndromic presentation, while surprisingly, non-syndromic ION are scarcely reported, with only 11 families with autosomal recessive optic atrophies related to OPA7 and OPA10 variants, or with the mitochondrial related Leber ION. Overall, consanguinity is a major cause of these diseases within North African countries, as 76.1% of IRD and 78.8% of ION investigated families were consanguineous, explaining the high rate of autosomal recessive inheritance pattern compared to the dominant one. In addition, we identified many founder mutations in small endogamous communities.

Short conclusion

As both IRD and ION diseases constitute a real public health burden, their under-diagnosis in North Africa due to the absence of physicians trained to the identification of inherited ophthalmologic presentations, together with the scarcity of tools for the molecular diagnosis represent major political, economic and health challenges for the future, to first establish accurate clinical diagnoses and then treat patients with the emergent therapies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02340-7.

End-stage crystalline maculopathy with retinal atrophy in Sjögren-Larsson syndrome: a case report and review of the literature

Sjögren-Larsson syndrome (SLS) is a rare, autosomal recessive neurocutaneous disorder. It is caused by the inheritance of sequence variants in the ALDH3A2 gene, which codes for fatty aldehyde dehydrogenase (FALDH). Universal signs of the condition are congenital ichthyosis, spastic paresis of the lower and upper limbs, and reduced intellectual ability. In addition to this clinical triad, patients with SLS experience dry eyes and decreased visual acuity caused by a progressive retinal degeneration. Examination of the retina in patients with SLS often reveals glistening yellow crystal-like deposits surrounding the fovea. This crystalline retinopathy often develops in childhood and is considered pathognomonic for the disease. The metabolic disorder typically shortens lifespan to half that of the unaffected population. However, now that patients with SLS live longer, it becomes increasingly important to understand the natural course of the disease. Our case describes a 58-year-old woman with advanced SLS whose ophthalmic examination illustrates the end-stage of the retinal degeneration. Optical coherence tomography (OCT) and fluorescein angiography confirm the disease is restricted to the neural retina with dramatic thinning of the macula. This case is unique since it is among the most advanced both in terms of chronological age and severity of retinal disease. While the accumulation of fatty aldehydes, alcohols, and other precursor molecules is the probable cause of retinal toxicity, a more complete understanding of the course of retinal degeneration may aid in the development of future treatments. The aim of our presentation of this case is to increase awareness of the disease and to foster interest in therapeutic research which may benefit patients with this rare condition.

Typical Neuroradiological Features of Sjogren-Larsson Syndrome

Sjogren-Larsson syndrome is a rare inherited autosomal recessive neurocutaneous disorder with typical findings on MRI. We describe the typical MRI and MR Spectroscopy findings in a clinically diagnosed case of Sjogren-Larsson syndrome.x

Novel and recurrent ALDH3A2 mutations in Italian patients with Sjögren-Larsson syndrome

Sjögren-Larsson syndrome (SLS; MIM#270200) is an autosomal recessive neurocutaneous disease caused by mutations in the ALDH3A2 gene for fatty aldehyde dehydrogenase (FALDH), a microsomal enzyme that catalyzes the oxidation of medium- and long- chain aliphatic aldehydes fatty acids. We studied two unrelated Italian SLS patients with ichthyosis, developmental delay, spastic diplegia and brain white matter disease. One patient was homozygous for a novel ALDH3A2 insertion mutation (c.767insA) in exon 5. The other SLS patient was a compound heterozygote for two previously reported mutations: a slice site mutation (c.1094C > T; S365L) in exon 7. Analysis of fibroblast RNA by RT-PCR indicated that the spice-site mutation caused skipping of exons 2 and 3. The c.1094C > T mutation, previously associated with two ALDH3A2 haplotypes, was found on a third distinct haplotype in our patient, which indicates that arose independently in this kindred. These results add to understanding of the genetic basis of SLS and will be useful for DNA diagnosis of this disease.