Inguinal lymph nodes agenesia in a patient with Schimmelpenning-Feuerstein-Mims syndrome with proven somatic KRAS mutation

Schimmelpenning-Feuerstein-Mims syndrome with orbital choristoma and KRAS mutation: a current review and novel case report

INTRODUCTION

Schimmelpenning-Feurstein-Mims Syndrome (SFMS) is a rare neurocutaneous disorder. Herein, we describe a novel case and review the phenotypic spectrum and molecular findings of SFMS from an ophthalmology perspective.

METHODS

Clinical case including presentation, management, pathology, and genetic analysis is described. A literature search on Schimmelpenning-Feuerstein-Mims and its synonyms, Linear nevus sebaceous syndrome, Organoid nevus syndrome, Jadassohn nevus phacomatosis, and Solomon syndrome, was conducted. An updated review and description of published cases with identified genetic mutations are described.

RESULTS

A 13-year-old boy with SFMS presented with acute right eye pain and an enlarging orbital mass. Excisional biopsy of the mass revealed an orbital choristoma. Genetic analysis of the orbital tumor confirmed a KRAS c.35 G>A, p.G12D mutation. A literature search revealed 19 cases of SFMS with mutations in the RAS-pathway. KRAS, HRAS, and NRAS mutations were identified in 74%, 21%, and 5% of patients, respectively. Ophthalmic pathology was seen in 83% of patients. Systemic findings varied and involved the skin, central nervous system, and eyes most commonly.

DISCUSSION

SFMS, a rare neurocutaneous disorder, results from postzygotic mosaic mutations in the RAS/MAPK pathway. Patients present with various systemic findings and ophthalmic manifestations occur in most cases. This is the first case description of a KRAS mutation identified in an orbital choristoma in SFMS. The disease is described under various names in the literature, and we propose that all syndromic cases with mosaic RAS mutations be reported under the eponym, SFMS.

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.

Classification of KRAS-Activating Mutations and the Implications for Therapeutic Intervention

Members of the family of RAS proto-oncogenes, discovered just over 40 years ago, were among the first cancer-initiating genes to be discovered. Of the three RAS family members, KRAS is the most frequently mutated in human cancers. Despite intensive biological and biochemical study of RAS proteins over the past four decades, we are only now starting to devise therapeutic strategies to target their oncogenic properties. Here, we highlight the distinct biochemical properties of common and rare KRAS alleles, enabling their classification into functional subtypes. We also discuss the implications of this functional classification for potential therapeutic avenues targeting mutant subtypes.

SIGNIFICANCE

Efforts in the recent past to inhibit KRAS oncogenicity have focused on kinases that function in downstream signal transduction cascades, although preclinical successes have not translated to patients with KRAS-mutant cancer. Recently, clinically effective covalent inhibitors of KRASG12C have been developed, establishing two principles that form a foundation for future efforts. First, KRAS is druggable. Second, each mutant form of KRAS is likely to have properties that make it uniquely druggable.