Coffin-Siris syndrome is a congenital condition that occurs as a result of a new or an inherited genetic mutation that follows an autosomal dominant pattern. Some of the features commonly associated with this condition include intellectual disability, developmental challenges, dysmorphic facial structures, and hypoplastic fingernails or toenails of the fifth digits.
Coffin-Siris syndrome (CSS) is an uncommon congenital disease that affects many systems in the body. It presents with a wide range of clinical features.
CSS can be caused by heterozygous genetic mutations in any of the genes that have been linked to the condition. Examples include the genes ARID1B (AT-rich interactive domain-containing protein 1B), and SMARCA4 (SWI/SNF related, matrix associated, actin dependent regulator of chromatin, subfamily a, member 4) . Although some mutations are inherited (according to an autosomal dominant pattern), many cases of CSS occur de novo .
Regularly reported features include intellectual and developmental impairment with varying severity, dysmorphic facial features, and dysplastic nails on the fifth digit. These are considered the major features of CSS. Typical CSS facies exhibit a wide mouth and nasal bridge, everted lips, downward slanting eyes, and thick eyebrows. The more frequently observed minor features of CSS include failure to thrive, short stature, microcephaly, and sparse scalp hair. In contrast, there may be excessive hair growth, usually involving the torso, face and upper limbs.
In the central nervous system (CNS), manifestations of CSS include seizures, Dandy-Walker malformation, hypotonia, and other anatomical abnormalities. Furthermore, patients diagnosed with CSS are also prone to abnormalities in other systems, such as the cardiovascular system (CVS). A few of the known CVS manifestations are exemplified by tetralogy of Fallot (ToF), atrial septal defect (ASD) or ventricular septal defect (VSD) . CSS may cause hearing problems, as well as visual impairment. Ocular abnormalities include cataracts and strabismus.
Various other minor features have been described, such as single palmar creases, low set ears, renal malformations, and gastrointestinal and skeletal abnormalities  . The latter may appear as spinal abnormalities such as scoliosis, often seen during childhood.
Individuals affected by CSS have a higher incidence of infections, compared with the general population, due to a higher susceptibility. Infections can occur in numerous parts of the body, including the respiratory and urogenital systems  .
Coffin-Siris syndrome may be diagnosed clinically through the assessment of presenting signs and symptoms. Although the type of feature presenting, whether major or minor, is important when considering the diagnosis of CCS, there is no set of standard diagnostic criteria for the condition . Hypoplasia or aplasia of the fifth digit nail and distal phalanx may be absent, and is not necessary for the diagnosis of CSS to be made. Genetic testing is used to confirm the diagnosis; however, prenatal detection of the condition is limited by the presence of spontaneous cases .