Nezelof syndrome is an autosomal recessive[6] congenital immunodeficiency condition due to underdevelopment of the thymus.

[7][8] Other symptoms are:[2] Genetically speaking, Nezelof syndrome is autosomal recessive.

the condition is thought to be a variation of severe combined immunodeficiency (SCID).

[8] However, the precise cause of Nezelof syndrome remains uncertain[3] In the mechanism of this condition, one first finds that the normal function of the thymus has it being important in T-cell development and release into the body's blood circulation[9] Hassal's corpuscles[10] absence in thymus(atrophy) has an effect on T-cells.

[3] The diagnosis of Nezelof syndrome will indicate a deficiency of T-cells,[11] additionally in ascertaining the condition the following is done:[3][4] The differential diagnosis for this condition consists of acquired immune deficiency syndrome and severe combined immunodeficiency syndrome[3][8] In terms of treatment for individuals with Nezelof syndrome, which was first characterized in 1964,[12] includes the following (effectiveness of bone marrow transplant is uncertain[4]) : peripheral: Purine nucleoside phosphorylase deficiency