Primary immunodeficiency or monogenic inflammatory bowel disease

Gene: SLC19A1

Green List (high evidence)

Comment on list classification: There are now 5 individuals from 4 unrelated families (1 distantly related) with biallelic variants in SLC19A1 and folate-dependent disease. 3 individuals had megaloblastic anemia, and 4 presented with immunodeficiency. 2 patients also noted to have chronic diarrhea. Slc19a1-null mice die early on due to failure of hematopoietic organs. Based on available evidence, this gene should be promoted to Green on Primary immunodeficiency or monogenic inflammatory bowel disease.

Created: 1 Apr 2026, 4:07 p.m. | Last Modified: 1 Apr 2026, 4:07 p.m.

Panel Version: 8.99

PMID: 32276275 Svaton et al., 2020
Case of recurrent severe megaloblastic anemia in a male patient with a homozygous SLC19A1 mutation c.634_636delTTC, p.Phe212del. First episode of severe anemia was at 15 yrs old with hemoglobin [Hb], 5 g/dL. Responded well to treatment with cyanocobalamin and folate.

PMID: 36517554 Gök et al., 2023
Report of two cousins carrying a homozygous pathogenic variant c.1042 G>A, p.G348R in SLC19A1, with symptoms of immunodeficiency associated with defects of folate transport. Patients benefited from folinic acid supplementation.
Case 1 - hospitalised at 15 days with lower respiratory tract infection and mouth sores; cytopenia (low Igg, reduced B cells and lymphocyte counts), high ferritin, low fibrinogen, and high triglycerides were noted. His sibling died at 3.5 months due to pneumonia.
Case 2 - cousin, presented with immunological and neurological issues.

PMID: 36745868 Shiraishi et al., 2023
2 patients with primary immunodeficiency caused by a homozygous missense mutation in SLC19A1 NM_194255:c.1042G>A (p.G348R).
P1 - 9yo boy with recurrent respiratory infections, chronic diarrhea, oral lesions, atopic dermatitis, recurrent fever and vomiting; brian MRI showed extensive periventricular white matter hyperintensities (lesions) and undeveloped myelinization for his age
P2 - 5yo boy, distant relative of P1; he had repeated episodes of oral lesions, fever, respiratory infections, and chronic diarrhea. Epilepsy and delayed development were also diagnosed. Brain tomography revealed cerebral calcification.
Both patients had anemia (megaloblastic), thrombocytopenia, hypogammaglobulinemia, and lymphopenia, as well as sparse gray hair.
Folic acid supplementation was beneficial and improved most symptoms.

Functional evidence: PMID: 11266438 Zhao et al., 2001 - SLC19A1-null mice died in utero, and survived until about 12 days if folic acid supplementation was given to the SLC19A1 +/- mother. The knockout mice showed a marked absence of erythropoiesis in bone marrow, spleen, and liver along with lymphoid depletion in the splenic white pulp and thymus.

The relationship between SCL19A1 and immunodeficiency 114, folate-responsive has been classified as Limited by the Primary Immune Regulatory Disorders GCEP in September 2025.
Sources: Literature

Created: 1 Apr 2026, 4:06 p.m.

Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal

Phenotypes
?Megaloblastic anemia, folate-responsive, OMIM:601775; Immunodeficiency 114, folate-responsive, OMIM:620603

Publications

• 32276275
• 36517554
• 36745868