Nezelof syndrome

Nezelof syndrome (also known as "Thymic dysplasia with normal immunoglobulins") is an autosomal recessive congenital immunodeficiency condition due to underdevelopment of the thymus. An association with CD44 has been proposed.

The defect is a type of purine nucleoside phosphorylase deficiency with inactive phosphorylase. This results in an accumulation of deoxy-GTP which inhibits ribonucleotide reductase. Ribonucleotide reductase catalyzes the formation of deoxyribonucleotides from ribonucleotides. Thus, DNA replication is inhibited and cells cannot replicate.