Certain problems are required to be present for diagnosis of FSS. All persons with FSS have the following problems: very small mouth (microstomia), whistling-face appearance (pursed lips), “H” or “V” shaped chin dimple and very obvious crease from the nostril to the corners of the mouth (nasolabial creases). Classically, persons also have Restricted movement in joints (contractures) of two or more body areas, often hands and feet, with fingers and toes frequently overlapping.
Many additional problems have been associated with FSS, especially problems of the face, including: over-crowded teeth (dental crowding), poorly aligned teeth (class II malocclusion), very high roof of the mouth (vaulted or highly arched palate), extra distance between the nose and upper lip (long philtrum), bulging ridges above the eyes (prominent superciliary ridges or frontal bossing), very small tongue (microglossia), drooping eyelids (blepharoptosis), cross-eyed problem (strabismus), extra inner skin-fold of the eye next to the nose (epicanthal folds), down-slanting eyelid folds (palpebral fissures), very small eyelid opening (blepharophimosis), sunken appearance of eyes (enophthalmos), widely spaced eyes (ocular hypertelorism), low set and tilted ears, mild to moderate hearing impairment, under-developed chin (microgenia), under-developed (micrognathia) and recessed (retrognathia) jaw, wide nasal bridge, small nose, under-developed nostrils (hypoplastic alae nasi), long face and flat mid-face (mid-face hypoplasia). Skull bones may come together too early (craniosynostosis) and a small skull (microcephaly).
Hand or Foot deformities may be present on both (bilateral) or only one (unilateral) side. Fingers (phalanges) may be tightly bent (camptodactyly) and pointed outward from the thumb (ulnar deviation or windmill vane appearance). The thumb (pollex) may be tightly bent into the palm (adducted or thumb-in-palm deformity). The wrist often has limited movement and is frequently bent up (dorsoflexed or cock-up deformity). Feet often resemble a golf club (Talipes equinovarus or club foot condition) and may have a rocker bottom appearance (vertical talus), with toes (phalanges) tightly bent (camptodactyly) and turned inward (metatarsus varus). Sometimes there is overriding of fingers or toes shortly after birth that improves spontaneously or with mild therapy.
Different deformities of the back, ribs, and chest have been observed. Many persons with FSS have humpback (kyphosis), swayback (lordosis) or sideways (scoliosis) curves in the back bones. If the abnormalities in the curves of the spine and breastbone are significant, they can restrict internal organs of the chest and abdomen and cause gastrointestinal, lung, and heart problems. In people with FSS, the muscles between the ribs (intercostal muscles) often are non-functional, making breathing and coughing difficult (reduced respiratory effort and tussive ability) and rarely causing harm to the lungs (pulmonary hypertension) and heart (right heart strain and cor pulmonale). Not being able to breathe deeply and cough well also can make it difficult to recover from lower respiratory infections. When present, the combination of severely abnormal curves of the backbone and non-functional muscles between the ribs (intercostal muscles) may result in chronic lung problems (reduced intrathoracic volume, impaired thoracic cage compliance, impaired exercise tolerance, reduced ventilation of oxygen, and restrictive pulmonary disease). Notably, there is no evidence of FSS directly causing lung or heart problems. Some of the indirect or secondary lung and heart problems that persons with FSS may experience because of non-functional muscles between the ribs and possibly other areas of the chest can resolve or have improvement with exercise and medical treatment. Less frequently, some people may have deformities of the ribs and breastbone (sternum) cartilage, causing either a sunken (pectus excavatum) or jutted out (pectus carinatum) appearance of the chest. Rarely, persons may have small openings in the spinal bones (spina bifida occulta).
Persons with FSS often have a short neck that does not move well and may have extra skin, giving a “webbed” appearance (pterygium colli). Hips and knees and, less frequently, shoulders and elbows may have limited movement (contractures) and dislocations. The knee cap (patella) may repeatedly partially dislocate (habitual subluxation). Joints with limited or no movement (contractures) may have decreased or absent reflexes (deep tendon reflexes). Some patients have experienced abdominal hernias (inguinal, epigastric).
Under-development of the jaw (micrognathia) may contribute to swallowing (dysphagia) and breathing problems (lower airway obstruction), but typically, patients have a very small tongue (microglossia), preventing breathing problems caused by the tongue that happen in patients with other conditions involving under-development of the jaw. Mouth breathing is caused by very thin (hypoplastic) nasal cartilages and narrowed nasal passages (nasopharynx). Poor coughing (tussive) ability and swallowing problems (dysphagia) may put the person with FSS at greater risk for airway obstruction and inhalation (aspiration) of food, saliva or vomit into the lungs, which may cause lower respiratory infections (bronchitis and pneumonia). Mouth breathing, which causes inhalation of unconditioned air and potentially aerosol droplets from people with contagious respiratory infections, may further complicate the potential respiratory risk for patients with FSS. Upper respiratory infections may progress more often to bronchitis or pneumonia infections, as well. Mouth breathing, swallowing problems (dysphagia), and the not uncommon need for a high calorie diet can also cause persons with FSS to be more at risk for developing dental cavities (caries). Persons may be more at-risk for middle ear infections, which can lead to hearing loss. Persons with FSS may also experience sinus infections and frontal Headaches more often because of deformities of the skull.
While severe swallowing problems (dysphagia) may reduce eating efficiency—slowing growth in infancy and childhood, swallowing problems (dysphagia) typically improve spontaneously with age. Rarely, dysphagia may not improve. Persons with FSS typically have difficulty creating a suction with the lips and mouth because of ineffective facial muscles. Persons with FSS are typically short and may be thin into early adulthood, while others are normal weight or overweight as adults. There are some reports of persons with FSS experiencing more chronic constipation, vomiting, and gastroesophageal reflux, suggesting that gut (visceral) muscle may be secondarily affected. A few persons with FSS seem to use energy at higher rates and require high calorie foods, but the cause is unknown.
Speech problems (dysphasia), which typically include both a nasal voice (hyponasality) and articulation problems, are caused by multiple structural and functional problems, specifically problems with regional muscles; a very small tongue (microglossia); highly arched roof of the mouth (hard palate); very thin (hypoplastic) nasal cartilages; narrowed nasal passages (nasopharynx); and under-developed facial bones (midface hypoplasia).
Except those who have had severe respiratory complications and not enough oxygen reached the brain, persons with FSS have normal intelligence. Most persons have developmental delays that are caused by physical deformities.
Because of head, neck, throat (pharynx) and mouth problems, it is challenging for healthcare providers to protect the airway of persons with FSS who are unconscious. It is also difficult for healthcare providers to access blood vessels to draw blood or give medicine or fluid. These problems seriously complicate anesthesia, sedation and surgery planning for persons with FSS.