SLC29A3 Pathogenic Variants Resulting in Dural Based Fibroinflammatory Mass Lesions and H Syndrome Treated With Cobimetinib: A Case Report.

Objectives: Pathogenic SLC29A3 variants are known to cause autosomal recessive disease with a spectrum of systemic involvement. We sought to expand on the spectrum of SLC29A3 variants and describe potential treatment.

Methods: We describe a case of newly diagnosed SLC29A3-related disorder, also known as H syndrome or familial histiocytosis, associated with CNS inflammatory pseudotumor and spinal cord compression.

Results: We present a 25-year-old man with recurrent dural based masses resulting in spinal cord and brain compression, hyperpigmented skin patches, proptosis, short stature, and elevated serum and spinal fluid inflammatory markers. Panel genetic testing revealed homozygous pathogenic variant c.1309G>A in the SLC29A3 gene resulting in a missense alteration (p. Gly437Arg). The patient was treated with cobimetinib with clinical, serologic, and radiographic improvement at 1-month follow-up.

Discussion: SLC29A3 variant may cause fibroinflammatory lesions involving the dura resembling the clinical spectrum of Rosai-Dorfman disease. Patients with SLC29A3 disease and neurologic signs or symptoms should undergo screening MRI for CNS involvement. MEK inhibition represents a novel treatment for this disorder.