Floating Harbor Syndrome

In 1973, Pelletier and Feingold described a young male who was seen at the Boston Floating Hospital with short stature, delayed speech and unusually triangular facial appearance. A further report of a similar case was published by Leisti et al. who had seen their patient at the Harbor General Hospital,  Torrance, California. They suggested the term Floating Harbor Syndrome.

There are under a 100 recognized individuals with a diagnosis of Floating Harbor Syndrome worldwide (2018).

Physical Attributes can include:

Scoliosis – Malformed Hips – Hearing Abnormalities – Stomach Disorders – Dental Anomilies – Microcephaly – Short Stature – Distinctive Facial Shape/Features

Speech and Language Deficits can include : Receptive and Expressive language delays

Sensory and Processing Disorders can be: Hyper and Hypo Sensory

Floating-Harbor syndrome is a Global Specific Developmental Delay that affects people in various ways. There are many disorders or differences to that of a typically developing person, and as this is a very rare syndrome, any related medical information, is extremely difficult to come by. Any relevant data that we can collect from parents or qualified professionals, helps everyone connected understand how best to help the people affected by Floating Harbor Syndrome (FHS for short).

Please be assured that it is not a case of one size fits all, and you may recognize some disorders and not others. There a vast number of disorders that have been associated with people diagnosed with Floating Harbor Syndrome, however there are many with reports of no association at all. If you think of FHS as a spectrum, where the severity of any disorder can be reported as zero, minimal, moderate, then upwards: there is no set rule that a person should match everything, just because it is listed as a symptom of having FHS.

Everyone affected is different, therefore parents should talk to their children’s physician or medical team about their specific case, associated symptoms and overall prognosis. It is vital however that the FHS child is monitored closely by specialized professionals throughout childhood, and parents are given every opportunity to share the experiences of their child from a parent’s perception. Working together is vital for a positive outcome.

Education for children with FHS is one of the big concerns for parents and the information provided here as a guidance for teachers, should be adhered to as much as possible; this is aimed to help the child have a positive learning experience. Click Here to view. Support on a one-to one basis would be suggested in an Educational environment, with specialized help.

Several factors including the small number of identified cases, the lack of large clinical studies, and the possibility of other genes influencing this disorder, prevent physicians from developing a complete picture of associated symptoms and prognosis. It is therefore important to note the following description of FHS, comes directly from reports from parents, qualified medical professionals and academic journals.

Sensory; High and Low pain threshold, Hypersensitivities to sensory input, Hypo sensitivities to sensory input, Hypersensitivity To Sounds, Hyposensitivity To Sounds, Hyposensitivity To Oral Input and Hypersensitivity To Oral Input. For a breakdown, please follow this link to our Sensory Processing Disorder section.

Speech and Language; Speech and language deficits are common in children with FHS. Expressive language deficits are most common and often most affected. Expressive language is the ability of a person to ‘output’ language or how people express themselves such as through speech or writing. It also encompasses the use of gestures and facial expressions. Some affected children also have receptive language deficits, in which they are unable to understand words and gestures. Affected individuals may have difficulty speaking (dysarthria) and exhibit a distinct, high-pitched nasally voice. In some cases, speech may be absent. Children may be described as having verbal dyspraxia, which refers to the difficulty or inability to coordinate the precise movements required to produce clear speech despite the absence of damage to the nerves or muscles. The severity of expressive and receptive language abnormalities can vary widely.

Physical attributes; Infants and children with FHS have distinctive facial features including a triangularly-shaped face; low-set ears; deep-set eyes with abnormally long eyelashes; thin lips; a broad, linear mouth; a prominent, triangular-shaped nose that is narrow at the root and broadens at the base; the bottom of the sheet of cartilage and bone (nasal septum) that separates the right and left nostrils (columella) may be low-hanging; the nostrils are large; and the groove that runs from the nose to the upper lip (philtrum) is short. These facial characteristics are the most distinctive features of FHS. Although they may change as an affected individual ages, the key features remain constant. In addition to growth deficiencies, children with FHS have a delay in bone aging in the first decade of life, which means that the rate of growth and calcification of the bones is slower than normal.

Affected individuals exhibit various skeletal malformations including short fingers and toes (brachydactyly); broad fingertips that give the appearance of clubbing; short, broad thumbs; and prominent joints. The pinkies may be fixed or ‘locked’ in a bent position (clinodactyly). Some individuals may have abnormalities of the collarbones (clavicles) including underdevelopment (hypoplasia) of the collarbone or the development of a ‘false joint’ (pseudoarthrosis). A false joint is a bony structure that usually develops at the site of a poorly united fracture that allows abnormal movement of the affected bones.

Early Developmental; Poor muscle tone is commonly seen in individuals with isodicentric chromosome 15 syndrome and contributes to delayed development and impairment of motor skills, including sitting and walking. In some cases, delayed growth may occur before birth (prenatal growth retardation) resulting in low birth weight. Typically, growth deficiencies become apparent during the first year of life. Affected children may be below average height for their age (short stature), and among the shortest 5 percent of their age group. In some cases, the onset of puberty may occur earlier than normal(Precocious puberty). Males may have undescended testicles (cryptorchidism) and hypospadias, a condition in which the tube that is connected to the bladder and discharges urine from the body (urethra) opens on the underside of the penis instead of the tip.

Additional issues have been reported in individuals with FHS including short bones in the hands (metacarpals); the presence of 11 pairs of ribs instead of 12; malformed (dysplastic) hips; abnormal curvature of the spine (kyphoscoliosis); seizures; backflow or leakage of the contents of the stomach into the oesophagus (gastroesophageal reflux); farsightedness (hyperopia); crossed eyes (strabismus); recurrent middle ear infections (otitis media); and conductive hearing loss.

Conductive hearing loss occurs when there is impaired transmission of sound from the outer or middle ear to the inner ear. The individual will shout and talk loudly. Normal hearing tests are not appropriate to pick up the affected areas, again, inform your physician of the above impaired transmission of sound. In some cases, affected individuals may exhibit kidney abnormalities such as cysts on the kidneys or swelling (distension) of the kidneys due to the abnormal accumulation of urine (hydronephrosis). This develops because of blockage within the urinary tract that prevents urine from being evacuated through the bladder. In some cases, there may be absence of the kidneys (agenesis).

Dental abnormalities are also common with FHS and it is of extreme importance that you should discuss your child’s background before any treatment starts. Dental anomalies may also occur including extra (supernumerary) teeth, delayed loss of primary (“baby”) teeth, abnormally small teeth (microdontia), and malocclusion, a condition in which the upper teeth are improperly positioned in relation to the lower teeth.

Psychological and behavioural issues; Attention hyperactivity, impulsivity, short attention span, anxiety, depression, immaturity, emotional detachment, low self-esteem, Cognitive functioning; Intellectual disability that is typically mild to moderate in degree has been reported.

Other disorders that have been reported in individuals with FHS include Coeliac disease, congenital heart defects, underactivity of the thyroid (hypothyroidism), and, in adulthood, high blood pressure (hypertension) and depression.

 

Genetics: 

Floating-Harbor syndrome is caused by a mutation in the SRCAP gene. Genes provide instructions for creating proteins that play a critical role in many functions of the body. When a mutation of a gene occurs, the protein product may be faulty, inefficient, or absent. Depending upon the functions of the particular protein, this can affect many organ systems of the body.

Investigators have determined that the SRCAP gene is located on the short arm (p) of chromosome 16 (16p11). Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Human body cells normally have 46 chromosomes. Pairs of human chromosomes are numbered from 1 through 22 and the sex chromosomes are designated X and Y. Males have one X and one Y chromosome and females have two X chromosomes. Each chromosome has a short arm designated “p” and a long arm designated “q”. Chromosomes are further sub-divided into many bands that are numbered.

In FHS, mutations in the SRCAP gene often occur as a new (sporadic or de novo) mutation, which means that in nearly all cases the gene mutation has occurred at the time of the formation of the egg or sperm for that child only, and no other family member will be affected. There are no silent carriers of FHS (i.e. if one carries a mutation in SRCAP, he/she will show signs of FHS).

Although most cases are due to sporadic mutations, dominant inheritance (where a trait is transmitted from either an affected mother or father to a child) has been documented in a few families. Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother. Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary for the appearance of the disease. The abnormal gene can be inherited from either parent, or can be the result of a new mutation (gene change) in the affected individual. The risk of passing the abnormal gene from affected parent to offspring is 50% for each pregnancy. The risk is the same for males and females.

The SRCAP gene creates (encodes) a protein that has several functions in the body. This protein is a cofactor (i.e. a substance required for a protein’s biological activity) for the CREB-binding protein (CREBBP). Mutations in the gene that produces CREB-binding protein cause Rubinstein-Taybi syndrome, a rare disorder with many overlapping symptoms to FHS.

We constantly strive to update information as and when it is available, therefore if you have anything to add, please contact us.

 

 

 

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