Clinical Guidance

To date no genotype-phenotype correlations are known.

Source: GeneReviews — "STAC3 Disorder"

Diagnostic Criteria

Formal diagnostic criteria for STAC3 disorder have not been established.

Suggestive Findings

STAC3 disorder (also known as Native American myopathy) should be suspected in individuals with the following clinical and laboratory findings.

Clinical findings

• Congenital myopathy

• Congenital weakness

• Myopathic facies, characterized by ptosis, inability to raise corners of mouth, and (in some individuals) hollowed-out cheeks from loss of facial musculature, which may cause an open-mouthed expressionless appearance with downturned corners of the mouth. Over time, the face often becomes long and narrow.

• Musculoskeletal anomalies

Source: GeneReviews — "STAC3 Disorder"

Differential Diagnosis

Table 3. Disorders with Facial Weakness and Hypotonia to Consider in the Differential Diagnosis of STAC3 Disorder

Management Guidelines

Evaluations Following Initial Diagnosis To establish the extent of disease and needs in an individual diagnosed with STAC3 disorder, the evaluations summarized (if not performed as part of the evaluation that led to the diagnosis) are recommended. Table 4. Recommended Evaluations Following Initial Diagnosis in Individuals with STAC3 Disorder

Source: GeneReviews — "STAC3 Disorder"

Clinical Guidance

Persons with STAC3 disorder are at increased risk for malignant hyperthermia (MH) crises when exposed to certain agents used with general anesthesia – most commonly volatile anesthetic gases (including halothane, isoflurane, and sevoflurane) and depolarizing muscle relaxants (e.g., succinylcholine and decamethonium). It is imperative that persons with STAC3 disorder discuss their diagnosis with anesthesiologists and treating physicians prior to surgical procedures to ensure that appropriate anesthetics are chosen to reduce the risk of MH.

Source: GeneReviews — "STAC3 Disorder"

Therapies Under Investigation

Search ClinicalTrials.gov in the US and EU Clinical Trials Register in Europe for access to information on clinical studies for a wide range of diseases and conditions. Note: There may not be clinical trials for this disorder.

Source: GeneReviews — "STAC3 Disorder"

Surveillance Guidelines

Table 6.

Recommended Surveillance for Individuals with STAC3 Disorder

System/Concern | Evaluation | Recommended Frequency

Growth

| PCP should monitor growth incl weight, height, head circumference. | At each visit

Neuromuscular

| Multidisciplinary neuromuscular clinic monitoring of:

• Respiratory status, speech development, swallowing function

• Musculoskeletal complications (e.g., scoliosis /or joint contractures)

| • Infants age 12 mos: every 3-4 mos

• Older children adults: every 6-12 mos

Cleft palate

| Multidisciplinary craniofacial team:

• Equipment techniques for feeding infants w/cleft palate

• Surgical repair timing type of procedure determined by team

• Anesthesiologist should be aware of risk of MH.

• Audiologic eval as part of craniofacial team as needed

| • Infants: visit frequency determined by feeding respiratory issues

• Children: varies depending on comorbidities; at least annually

Feeding

| Multidisciplinary craniofacial team in conjunction w/PCP:

• Measure growth parameters.

• Evaluate nutritional status safety of oral intake.

• Consider clinical feeding eval /or video fluoroscopic swallow study.

| At each visit

Respiratory

| Pulmonologist:

• Assessment of pulmonary status pulmonary function testing

• Polysomnography

• Evaluate for signs of ascending or descending aspiration.

| Clinical eval at least annually but likely more often during infancy or when any signs of respiratory insufficiency, aspiration, /or sleep apnea develop

Speech

| Multidisciplinary craniofacial team:

Source: GeneReviews — "STAC3 Disorder"