Novel immunodeficiency caused by homozygous mutations of SLC19A1

The male proband suffered from infancy oral lesions, recurrent fever, diarrhea, vomiting, atopic dermatitis, dark discoloration patches on his skin and lip fissures; he suffered from anemia (megaloblastic), thrombocytopenia, hypogammaglobulinemia and lymphopenia; his growth and development are delayed. Whole exome sequencing identified only one variant predicted to have high impact and to potentially explain the patient’s phenotype, a homozygous missense chr21:46950793:C:T (hg19) SLC19A1 NM_194255:c.1042G>A (p.G348R). Sanger sequencing and segregation analysis confirmed the presence of the homozygous SLC19A1 c.1042G>A (G348R) missense variant in the proband, with a heterozygous state in his family. The same homozygous SLC19A1 variant was identified in a distantly-related male patient with a similar phenotype presentation, while his healthy family members were heterozygous. SLC19A1 is a folate transporter, and thus folic acid supplementation was performed for the proband: platelet counts normalized rapidly and anemia improved; hair and skin discoloration, mouth lesions and chronic diarrhea improved. In contrast, neurological and developmental issues remained unchanged and treatment had only a partial effect on the immune system. This further confirmed the causal role of SLC19A1 for the proband's condition.

• Type: Exome Sequencing
• Archiver: European Genome-Phenome Archive (EGA)