Hoyeraal-Hreidarsson Syndrome

Background and History: 

This is a rare inherited condition that has widespread signs and symptoms throughout the body.  It is sometimes considered to be a form of dyskeratosis congenita which is discussed elsewhere in this database.  Among the more serious problems that often lead to a shortened lifespan are reduced resistance to infections and failure of the bone marrow to make normal blood cells.

Clinical Correlations: 

Infants grow slowly in the uterus and are often born with low birth weight.  A small head (microcephaly) is usually evident at birth.  Many infants fail to thrive and have a global developmental delay.  Difficulty with balance and unsteadiness soon become apparent.  Anemia and sometimes bleeding tendencies also occur early and laboratory testing reveals that the bone marrow is not producing blood cells properly.

This is an extremely rare disorder and it is doubtful that we know the full clinical nature of this disorder.  There are often signs of dyskeratosis congenita with unusual skin pigmentation, abnormal nails, sparse hair, and scarring of oral membranes and those of the eye (conjunctiva or outer covering).


This is an X-linked disorder caused by a changed (mutated) gene on the X-chromosome.  It is therefore primarily a male disease although affected females have been reported.  Females have two X chromosomes, and generally only one carries the mutation so that they do not have this disorder (the other normal X-chromosome counterbalances the mutation).  Males only transmit their Y chromosome to their sons so it is the mother with the mutation who can transmit it to her sons with a 50% probability for each pregnancy.

Diagnosis and Prognosis: 

This rare disorder requires a multidisciplinary team for its diagnosis.  An MRI image can be helpful to show the underdevelopment of the brain structures.  No effective treatment is available and most infants do not live beyond 2-3 years, primarily due to the lack of a functioning bone marrow, or a serious infection.

Additional Information
X-linked recessive, carrier mother
X-linked recessive, father affected