ABCD syndrome is a rare genetic disorder that features albinism, black lock at temporo-occipital region, cell migration disturbance of the neurocytes of the gut, and sensorineural deafness. The main symptoms of the disease gave it a name as acronym – ABCD.
ABCD syndrome is congenital. It mainly affects skin and hair color and intestinal function. ABCD syndrome was initially suggested as a new discovered disease, but it is in fact the same condition as Shah-Waardenburg syndrome (Waardenburg syndrome type 4A).
The disease is caused by the mutations in the EDNRB (Endothelin Receptor Type B) gene located on the 13th chromosome. This change is inherited as an autosomal recessive trait. This means that to develop an illness a person should have this mutation in both copies of the gene (so-called homozygous mutation). The intestinal affection distinguishes ABCD syndrome from BADS – a condition that involves black locks, albinism and deafness.
As long as the ABCD is a genetic disorder anyone with a family history of the Waaderburg synrome, albinism, congenital intestines’ dysfunction, inherited deafness or blindness is at risk. The main method to prevent the disease is a genetic counseling that enables couples to prepare for pregnancy, helps provide information about the genetic diseases and raising an affected child, disease’s administration and future pregnancies.
Albinism is characterized by the pale hair and skin color much lighter than the parents and siblings of the person have. It also causes abnormalities in the eyes, such as photophobia (sensitivity to light), nystagmus (rapid involuntary back-and-forth movement of the eyes) and extreme myopia (nearsightedness) or hypermetropia (farsightedness). Affected people have black locks at the temporo-occipital region along Blashko lines (lines of normal cell development in the skin) and blue or grey irises that are similar to irises of blind people. Sometimes heterochromic irides occur (two irides have different color). In the areas of leukoderma (depigmented areas) abnormal melanocytes are found.
Children are born with hearing dysfunction called sensorineural deafness that progresses to a complete hearing loss. The intestinal dysfunction causes poor nutrition, poor weight gain, abnormal bowel movements and is the most dangerous and life threatening symptom of the disease. The reason of intestines’ failure is the disrupted migration of neurocytes of the intestines that leads to agangliosis so that the intestines get no neural signals and fail to move the food along the digestive tract. The disorder of intestines’ function is called the Hirschsprung’s disease (congenital megacolon – enlarged large bowel).
The disease can be diagnosed early after the labour. The newborn fails to pass meconium (the first stool) within first 48 hours of life. The children may vomit (the vomited substance is green or brown), they present the swelling of the abdomen due to the big amount of gases and diarrhea with blood. If the disease wasn’t initially recognized children experience constipation.
Diagnosis is based on the typical clinical image, X-ray or MRI of the abdominal organs and hearing testing. The diagnosis is confirmed with the DNA testing (the mutation of EDNRB gene on the 13th chromosome is present).
There is no specific treatment of the disordered, so the symptoms assessment is recommended. The intestines’ movement failure should be diagnosed as soon as possible or the child will die during infancy. The early treatment of the Hirshprung’s disorder includes colostomy (the surgical procedure of creating an opening (stoma) by drawing the healthy end of the large intestine through an incision in the anterior abdominal wall and suturing it), colectomy (surgical removal of the all or the part of the colon) or laxative administration.
Unfortunatly there is no way of hearing loss prevention. Although hearing aids and implants that require surgical implantation are accessible.