Patient with recurrent mosaic KRAS variant: Rare oculoectodermal syndrome with severe neurologic phenotype

Calcified Sclero-Choroidal Choristomas in Mosaic RASopathies: A Description of a New Imaging Sign

PURPOSE

To evaluate the imaging and clinical features of unusual calcified lesions seen in the fundus of patients with mosaic RASopathy.

DESIGN

Single-center retrospective observational study.

SUBJECTS

Ten eyes with calcified fundus lesions in 7 patients with mosaic RASopathy.

METHODS

The lesions were evaluated with fundus photography, oral fundus fluorescein angiography, B-scan ultrasonography, magnetic resonance imaging (MRI), and computed tomography (CT) scan where available.

MAIN OUTCOME MEASURES

The imaging characteristics of calcified fundus lesions were assessed.

RESULTS

We found 7 patients with mosaic RASopathies, 5 men and 2 women (3 with linear sebaceous nevus syndrome, 3 with oculoectodermal syndrome, and 1 with encephalocraniocutaneous lipomatosis) with molecular confirmation in 5 cases, all 5 having KRAS-pathogenic variants. Calcified fundus lesions were identified in 10 eyes (bilateral in 3 patients), appearing as slightly elevated, creamy-yellow lesions around or adjacent to the optic nerve, extending supero-nasally; all but 2 of these lesions involved both the choroid and sclera, with 2 of them only involving the sclera at the time of examination. One case developed a choroidal neovascular membrane necessitating intravitreal bevacizumab injections. All 7 patients had B-scan ultrasonography, and the lesion appeared as a hyperechogenic area with an acoustic shadow posteriorly despite reduced gain. Five patients had MRI, and where fundus lesions were present, there was a focal defect in the sclero-choroidal layer. Four patients had a CT scan, and all 4 showed calcifications affecting both the posteromedial sclero-choroid and adjacent medial rectus muscle. Two of these patients had normal eye movements, 1 had a unilateral fixed adducted eye and a vestigial fibrous medial rectus muscle seen in imaging and intraoperatively, and the fourth had marked exotropia with a right gaze deficit affecting both eyes.

CONCLUSIONS

We propose that the lesions seen in this cohort are calcified sclero-choroidal choristomas and should be suspected in mosaic RASopathies when creamy-yellow lesions are seen in the fundus. If identified, the possibility of choroidal neovascularization should be considered during follow-up. In all cases where a CT scan was performed, a novel sign of sclero-muscular calcification involving the medial rectus muscle was seen.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Mosaic RASopathies concept: different skin lesions, same systemic manifestations?

BACKGROUND

Cutaneous epidermal nevi are genotypically diverse mosaic disorders. Pathogenic hotspot variants in HRAS, KRAS, and less frequently, NRAS and BRAF may cause isolated keratinocytic epidermal nevi and sebaceous nevi or several different syndromes when associated with extracutaneous anomalies. Therefore, some authors suggest the concept of mosaic RASopathies to group these different disorders.

METHODS

In this paper, we describe three new cases of syndromic epidermal nevi caused by mosaic HRAS variants: one associating an extensive keratinocytic epidermal nevus with hypomastia, another with extensive mucosal involvement and a third combining a small sebaceous nevus with seizures and intellectual deficiency. Moreover, we performed extensive literature of all cases of syndromic epidermal nevi and related disorders with confirmed pathogenic postzygotic variants in HRAS, KRAS, NRAS or BRAF.

RESULTS

Most patients presented with bone, ophthalmological or neurological anomalies. Rhabdomyosarcoma, urothelial cell carcinoma and pubertas praecox are also repeatedly reported. KRAS pathogenic variants are involved in 50% of the cases, especially in sebaceous nevi, oculoectodermal syndrome and encephalocraniocutaneous lipomatosis. They are frequently associated with eye and brain anomalies. Pathogenic variants in HRAS are rather present in syndromic keratinocytic epidermal nevi and phacomatosis pigmentokeratotica.

CONCLUSION

This review delineates genotype/phenotype correlations of syndromic epidermal nevi with somatic RAS and BRAF pathogenic variants and may help improve their follow-up.