4p deletion syndrome is caused by the loss of a small part (microdeletion) on the short arm – called p for petite – of chromosome 4. The loss of genes on that region leads to several developmental and physical characteristics. Also known as Wolf-Hirschhorn syndrome by the two geneticists who first reported it in 19651,2, the condition occurs in 1 in 50,000 births3,4. Like many other rare conditions, this is likely an underestimate caused by misdiagnosis due to complexity and variability of symptoms, or non-diagnosis. Interestingly, the female to male ratio of incidence is 2:14,5.
The size of the deletion determines the number of genes lost, and the location of the deletion specifies which genes are lost. Both these factors define the range of symptoms and the severity of the condition in each individual with Wolf-Hirschhorn, along with their life expectancy. Symptoms vary depending on the characteristics of the deletion, but almost everyone has distinctive facial features – a broad, flat nasal bridge and a high forehead, receiving the characteristic ‘Greek warrior helmet’ appearance. A small chin and head, poorly formed ears and downturned mouth may also be present. Children may experience problems with feeding and gaining weight, have weak muscle tone, underdeveloped muscles and short stature. Skin and skeletal abnormalities, like scoliosis and cleft lip and palate may exist. Motor skills may be delayed, and intellectual disability ranges from mild to severe. Cardiovascular defects, poor immune system and seizures that are resistant to treatment are common, however; the latter tend to disappear with age3,4,5. Although language skills and verbal communication are weak, socialization skills tend to be strong. There is no cure for Wolf-Hirschhorn syndrome; treatment is symptomatic through multidisciplinary management that addresses each patient’s specific needs. Physical, occupational and language therapy are beneficial, especially when initiated as early as possible.
Typical to other chromosomal conditions, up to 90% of Wolf-Hirschhorn cases occur de-novo (at random), during mistakes when the reproductive cells (egg or sperm) are created, or fused together4,5. A small percentage inherits the condition if one of their parents unknowingly has a balanced translocation (chromosomal rearrangement where all the genetic material is present but not in the right order) involving chromosome 44,5. If an unbalanced part of the translocation passes to the next generation, health problems may be caused due to the genetic loss. Mosaic forms of Wolf-Hirschhorn also exist, where some cells carry the normal number of chromosomes and others have the 4p deletion.
Postnatal diagnosis is lengthy and complicated – if achievable – due to the complexity of symptoms and the small size of the deletion. Prenatal detection of Wolf-Hirschhorn syndrome is possible via NIPT, with confirmatory diagnosis achieved by chorionic villus sampling (CVS) or amniocentesis. Safe and early detection of the condition is invaluable in helping prospective parents and physicians to evaluate their options and start a therapy plan to remedy symptoms as early as possible.
4p16.3 deletion, the loss of segment 16 on the short arm (p) of chromosome 4, is the most common form of the condition – which is why April 16 was chosen as Wolf-Hirschhorn Awareness day. Promoting knowledge and information on the condition is integral in advancing medical therapy options, along with patient diagnosis and quality of life.
NIPT results, possible next steps and clinical management should always be fully discussed with your healthcare provider. VERACITY and VERAgene both detect 4p deletion, amongst other common genetic disorders, from the 10th week of pregnancy. To learn more please visit www.nipd.com
- Hirschhorn K. et al. (1965) ‘Deletion of short arms of chromosome 4-5 in a child with defects of midline fusion’. Humangenetik; 1(5): 479 – 482.
- Wolf U. et al. (1965) ‘Deficiency on the short arms of a chromosome No. 4’. Humangenetic; 1(5): 197-413.
- Genetics Home Reference (2019), https://ghr.nlm.nih.gov/condition/wolf-hirschhorn-syndrome
- Orphanet (2019), https://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=280
- Wolfhirschhorn.org, The real story about Wolf-Hirschhorn syndrome (2013), http://wolfhirschhorn.org/