Floating-Harbor Syndrome

A multiple congenital anomalies/dysmorphic syndrome-intellectual disability that is characterized by facial dysmorphism, short stature with delayed bone age, and expressive language delay.

Epidemiology

Floating-Harbor syndrome prevalence and incidence are unknown. Around 100 cases have been reported in the literature to date.

Clinical description

Facial features include a triangular-shaped face, a prominent bulbous nose with a broad nasal bridge, a wide columella, deep-set eyes with long eyelashes, a wide mouth with a thin upper lip, low-set ears and sometimes broad thumbs and big toes. The speech defect is marked by impairment of expressive language and is often associated with a peculiar hypernasal voice. Stature is usually reported to be below the third percentile and between 2 and 4 SD below the mean. Bone age is always delayed. Other variable manifestations include celiac disease, pseudoarthrosis of the clavicle, intellectual disability, dental anomalies (malocclusion, microdontia, supernumerary upper teeth), a short neck, brachydactyly, and clinodactyly of the 5th finger. Associated genitourinary and cardiac anomalies have been reported in a few cases.

Etiology

The syndrome is associated with heterozygous mutations in exon 33 or mostly in exon 34 of the SRCAP gene (16p11.2), with two recurrent mutations (Arg2444* and Arg2435*). SRCAP encodes an ATPase which is involved in chromatin remodeling and is the cofactor of CREBBP, the gene responsible for Rubinstein-Taybi syndrome.

Diagnostic methods

Diagnosis is based on clinical examination and can be confirmed by genetic testing.

Differential diagnosis

The differential diagnosis should include other dysmorphic syndromes, in particular Rubinstein-Taybi syndrome.

Antenatal diagnosis

Prenatal diagnosis can be considered for families in which the disease-causing mutation has been identified.

Genetic counseling

The majority of reported cases are sporadic, but a few familial cases with autosomal dominant inheritance have been reported.

Management and treatment

Management is only symptomatic. Patients may benefit from developmental and educational programs and should receive regular orthodontic care. Growth hormone therapy may be of benefit in some patients.

Prognosis

Despite the presence of short stature and learning difficulties, in general patients appear to remain in good health and have a good quality of life.