Background
Wolf-Hirschhorn syndrome (WHS) is a disorder caused by irregularities on the short arm of chromosome 4 (4p). It is characterized by intellectual disabilities and the Greek warrior helmet appearance of the nose and forehead, as well as multiple other defects (skeletal, cardiovascular, and urogenital).
Cooper and Hirschhorn first documented WHS in 1961. [1] They described a child with midline fusion defects. In 1965, back-to-back publications in Humangenetik by Hirschhorn et al and Wolf et al brought the disease to the attention of geneticists and other medical professionals. [2, 3] Numerous cases were subsequently published. (See the images below.)
A child with Wolf-Hirschhorn syndrome. Note the characteristic dysmorphic facial features, including prominent glabella, hypertelorism, beaked nose, and frontal bossing, collectively described as "Greek warrior helmet" facies.
A girl with Wolf-Hirschhorn syndrome showing characteristic features of the condition.
Pathophysiology
WHS results from irregularities of the distal short arm of chromosome 4, including deletions of varying size (most common) and microduplications. Several genetic mechanisms have been described (see the image below):
-
De novo deletion (50-60% of cases)
-
Unbalanced translocation (40-45% of cases) - Either de novo or inherited from a parent with a balanced translocation
-
Other complex rearrangements, leading to a 4p16.3 deletion - Ring 4 chromosome, 4p-mosaicism
G-banded karyotype showing deletion of 4p, derived from the mother, with balanced translocation (4p;8p).
Diagnosis is made by confirming a deletion in the WHS critical region (WHSCR) using conventional chromosome analysis, fluorescence in situ hybridization (FISH), or chromosomal microarray.
Evidence strongly supports the idea that the ‘‘core’’ phenotype (distinctive facial appearance, intellectual disability, growth delay, and seizures or electroencephalographic anomalies) is due to haploinsufficiency of several genes on distal 4p, including WHSC1, WHSC2, TACC3, FGFR3, and LETM1. [4] . Therefore, WHS represents a contiguous gene syndrome with contribution of genes located in the terminal 4p16.3 region, within a 1.5-1.6 Mb region.
The presence of a true genotype-phenotype correlation is controversial, as some studies have indicated that there is not always a correlation between the deletion's size and the severity of the clinical findings [5] .
Epidemiology
Frequency
United States
The frequency of WHS is estimated to be 1 case per 50,000 births to 1 case per 20,000 births. [6, 7]
Mortality/Morbidity
Mortality rate is estimated at 34% in the first 2 years of life. However, because many affected children die before the anomaly is diagnosed or suspected, the mortality rate is underestimated. The usual cause of death is a heart defect, aspiration pneumonia, infection, or seizure.
Prenatal mortality rate of Wolf-Hirschhorn syndrome is not significantly augmented because 4p deletions are not reported as an increase in spontaneous abortions.
Associated adulthood morbidity includes congenital heart defect; marked growth failure; contracture of hands, wrists, and feet; poor development of secondary sexual characteristics; and severe growth and intellectual impairment.
Race
Wolf-Hirschhorn syndrome has no ethnic predilection.
Sex
Wolf-Hirschhorn syndrome is more common in females than in males, with a male-to-female ratio of 1:2.
Age
Usually, the condition is detected in the newborn period because of dysmorphic features.
Prognosis
Wolf-Hirschhorn disease is associated with frequent stillbirths, perinatal deaths, and death within the first year of life. If patients survive beyond infancy, their neurodevelopment progresses slowly but constantly. The clinical spectrum is wider than previously suspected.
Patients with WHS are at risk for the following:
-
Seizures
-
Failure to thrive
-
Cognitive deficits
-
Motor deficits
-
Deficits in autonomy and sphincter control
Seizures
Seizures are a major concern for patients with WHS and are typically hard to control, especially early on. However, rapid diagnosis and treatment leads to improved control and outcomes. The majority of patients with WHS experience a decrease in the frequency of seizures after age 5 years, [8] and in approximately 50% of patients, seizures resolve by age 13 years.
Failure to thrive
Growth parameters are typically below the second percentile. Growth charts specific for children with WHS are available. [9]
Cognitive deficits
Severe intellectual disabilities are observed in the majority of patients (65%); however a broad range can be seen, including mild and moderate intellectual disability in 10% and 25% of patients, respectively. [10]
Expressive language is typically limited to guttural or disyllabic sounds. However, a minority of patients (<10%) are able to communicate using simple sentences.
Comprehension is typically context specific and limited to simple orders. Intent to communicate is present in most patients.
Motor deficits
About 45% of patients are able to walk, either independently (25%) or with support (20%). Walking is significantly delayed in these patients, being achieved between ages 2 and 12 years.
Autonomy and sphincter control
Only about 10% of patients achieve daytime sphincter control (typically between ages 8 and 14 years). Ten percent of patients are able to feed themselves, while about 20% can assist with dressing/undressing.
Adult health risks
In adulthood, patients with WHS are at risk for the following:
-
Chronic kidney disease
-
Malignancies - Specifically liver adenomas
Patient Education
The following websites contain updated information for patients and their families:
-
A child with Wolf-Hirschhorn syndrome. Note the characteristic dysmorphic facial features, including prominent glabella, hypertelorism, beaked nose, and frontal bossing, collectively described as "Greek warrior helmet" facies.
-
A fetus with Wolf-Hirschhorn syndrome. Note the presence of "Greek warrior helmet" facies.
-
The result of a fluorescence in situ hybridization (FISH) study of a patient with Wolf-Hirschhorn syndrome. FISH photograph shows deletion of a locus-specific probe for the Wolf-Hirschhorn critical region (absence of a probe signal at 4p16.3).
-
G-banded karyotype showing deletion of 4p, derived from the mother, with balanced translocation (4p;8p).
-
A girl with Wolf-Hirschhorn syndrome showing characteristic features of the condition.
