pancytopenia

Hoyeraal-Hreidarsson Syndrome

Clinical Characteristics

Ocular Features

Little is known about the ocular signs in this rare disorder.  As many patients have systemic features of dyskeratosis congenita, however, it is possible that some of the ocular findings such as conjunctival and corneal scarring and lid margin distortion might be similar.  Hoyeraal-Hreidarsson syndrome, though, is a more severe disease and many infants may die before the mucocutaneous manifestations appear.  At least one patient has had an exudative retinopathy similar to that seen in R√©v√©sz syndrome (268130).  Epiphora and a preretinal hemorrhage have also been reported.

Systemic Features

Features of pancytopenia usually appear after 5 months of age while growth retardation and microcephaly are evident soon after birth.  The marrow may show progression to myelodysplasia.  Birth weight is usually low.  Truncal ataxia and axial hypotonia have been reported and MRI imaging reveals cerebellar hypoplasia.  Global developmental delay is a common feature and a few patients have seizures.  Susceptibility to infection has been noted but the basis for an immunodeficiency remains elusive.  Some patients have signs of dyskeratosis congenita such as sparse hair, nail dysplasia, and a reticular pattern of skin pigmentation.

Genetics

This is an X-linked disorder resulting from mutations in the DKC1 gene (Xq28) active in telomere maintainence.  As expected, the vast majority of affected individuals are male but at least 3 females have been reported. The same gene is also mutated in the X-linked form of dyskeratosis congenita (305000) suggesting that the two are allelic.  There are clear clinical differences, however, as severe developmental delay, immunodeficiency, cerebellar hypoplasia, and microcephaly are generally not present in the latter disorder.

There is evidence for telomere length variations in this syndrome and in dyskeratosis congenita.  Homozygous mutations in RTEL1 (regulator of telomere length helicase 1) (20q13.33) have also been found in these conditions.

Treatment Options

No effective treatment has been reported.

References

Le Guen T, Jullien L, Touzot F, Schertzer M, Gaillard L, Perderiset M, Carpentier W, Nitschke P, Picard C, Couillault G, Soulier J, Fischer A, Callebaut I, Jabado N, Londono-Vallejo A, de Villartay JP, Revy P. Human RTEL1 Deficiency Causes Hoyeraal-Hreidarsson Syndrome With Short Telomeres and Genome Instability. Hum Mol Genet. 2013 Apr 15 [Epub ahead of print].

PubMed ID: 
23591994

Pearson T, Curtis F, Al-Eyadhy A, Al-Tamemi S, Mazer B, Dror Y, Abish S, Bale S, Compton J, Ray R, Scott P, Der Kaloustian VM. An intronic mutation in DKC1 in an infant with H√∏yeraal-Hreidarsson syndrome. Am J Med Genet A. 2008 Aug 15;146A(16):2159-61.

PubMed ID: 
18627054

Yaghmai R, Kimyai-Asadi A, Rostamiani K, Heiss NS, Poustka A, Eyaid W, Bodurtha J, Nousari HC, Hamosh A, Metzenberg A. Overlap of dyskeratosis congenita with the Hoyeraal-Hreidarsson syndrome. J Pediatr. 2000 Mar;136(3):390-3.

PubMed ID: 
10700698

Ohga S, Kai T, Honda K, Nakayama H, Inamitsu T, Ueda K. What are the essential symptoms in the Hoyeraal-Hreidarsson syndrome? Eur J Pediatr. 1997 Jan;156(1):80-1.

PubMed ID: 
9007502