J Clin Neurol.  2022 Mar;18(2):214-222. 10.3988/jcn.2022.18.2.214.

Novel RAB3GAP1 Mutation in the First Tunisian Family With Warburg Micro Syndrome

• Kerkeni N
• Kharrat M
• Maazoul F
• Boudabous H
• M’rad R
• Trabelsi M

• KMID: 2526873
• DOI: http://doi.org/10.3988/jcn.2022.18.2.214

Abstract

Background and Purpose
Warburg Micro syndrome (WARBM) is a rare autosomal recessive genetic disease characterized by ocular, neurologic, and endocrine anomalies. WARBM is a phenotypically and genetically heterogeneous syndrome caused by mutations in RAB3GAP1, RAB3GAP2, RAB18, and TBC1D20. Here we present the clinical and genetic characterization of a consanguineous Tunisian family with a WARBM phenotype presenting two pathogenic variations, one of which is on RAB3GAP1.
Methods
We applied whole-exome sequencing (WES) to two affected young males presenting a WARBM-compatible phenotype.
Results
We reveal a new variation in RAB3GAP1 (NM_012233.3: c.297del, p.Gln99fs) and another variation in ABCD1 (NM_000033: c.896A>G, p.His299Arg). Each of these mutations, which in silico predictions concluded as being pathogenic variations, affects a critical protein region. Both affected males presented a WARBM-compatible phenotype, with severe intellectual disability, severe developmental delay, postnatal growth delay, postnatal microcephaly, congenital bilateral cataracts, general hypotonia, and a thin corpus callosum without a splenium. However, intrafamilial clinical heterogeneity was present, since only the oldest child had large ears, microphthalmia, foot deformities, and a genital anomaly, and only the youngest child had microcornea. Despite the mutation identified in ABCD1, our patients did not have any Xlinked symptoms of adrenoleukodystrophy disorder that are usually caused by ABCD1 mutations, which prompted our interest in clinical monitoring.
Conclusions
WES analysis of a consanguineous Tunisian family with WARBM revealed a novel variation in RAB3GAP1 (NM_012233.3: c.297del, p.Gln99fs) that is most likely pathogenic and allowed us to confirm the diagnosis of WARBM.

Keyword

Warburg Micro syndrome; RAB3GAP1 protein; human; ABCD1 protein; human; mutation; whole exome sequencing