Ligase IV Syndrome is a rare condition that results in impaired DNA damage repair.


Inheritance: autosomal recessive


Gene affected: LIG4 on 13q33-q34. This encodes DNA ligase IV, which is a component of the non-homologous end-joining pathway of DNA repair.


Disease severity is determined by the type of mutation. Missense mutations are associated with some residual enzyme function and have mild disease. Nonsense mutations with truncation show no residual enzyme function and severe disease.


Clinical features:

(1) microcephaly

(2) prominent nose (large and/or long)

(3) mental retardation or developmental delay

(4) genital abnormalities

(5) variable skin abnormalities

(6) recurrent infections

(7) radiosensitivity


Laboratory findings:

(1) pancytopenia secondary to bone marrow failure

(2) immunodeficiency



(1) malignancies


To read more or access our algorithms and calculators, please log in or register.