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At a glance

It is a syndrome characterized by laryngotracheal stenosis, mental retardation, short stature, maxillary hypoplasia, prognathism, severe midface hypoplasia, short palpebral fissures, short philtrum, microstomia, generalized muscle hypertrophy, decreased joint mobility, cryptorchidism, cardiac anomaly, and sensorineural deafness. The cardiovascular anomaly include congenital heart defects, long- and short-stenotic stenosis of the aorta and peripheral arteries, pericardial effusion, constrictive pericarditis, restrictive cardiomyopathy, and hypertension. The involvement of the respiratory system shows choanal stenosis, laryngotracheal narrowing, obstructive airway disease, and restrictive pulmonary disease. A pyloric stenosis is often seen and surely a reason for early surgery. The onset of the disease is at infancy or early childhood.

Synonyms

Growth-Mental Deficiency Syndrome of Myhre; Laryngotracheal Stenosis Arthropathy Prognathism Short Stature Syndrome; LAPS Syndrome.

History

It was first described by Selma A. Myhre, an American pediatrician, in 1981.

Incidence

The exact incidence remains unknown. There are only 60 cases reported in the medical literature.

Genetic inheritance

It is believed inherited as an autosomal dominant pattern. All probands with Myhre Syndrome reported to date have the disorder as a result of a de novo SMAD4 pathogenic variant.

Clinical aspects

Maxillary hypoplasia, prognathism, midface hypoplasia, and thick calvaria represent the most characteristic features. Patients affected may also present a laryngotracheal stenosis significant enough to cause severe airway issues and become life-threatening with age. There are short palpebral fissures and blepharophimosis at the physical examination. Large nose with prominent root and short philtrum is present, with a small mouth and thin upper lip. The thorax has large flat vertebrae with large pedicles. Other bone abnormalities include hypoplastic iliac wings, brachydactyly, and limited joint mobility of short tubular bones. Muscles are hypertrophied. Abnormal EEG and congenital heart defects. Cryptorchidism. Prenatal and postnatal growth deficiencies are seen in association with mental retardation. Early-onset mixed conductive and sensory-type deafness occurs. Radiologically, several particularities are reported and include thickened calvaria, broad ribs, hypoplastic iliac wings, shortened long and tubular bones, and large, flattened vertebrae with large pedicles.

Precautions before anesthesia

It is highly recommended to assess the craniofacial features, especially the severity of the maxillary and midface hypoplasia. The presence of prognathism is not a guarantee to an easy direct laryngoscopy and tracheal intubation. Furthermore, the possibility of mild-to-severe laryngotracheal stenosis (the mild one being the most susceptible to affect tracheal intubation as the diagnostic will be more difficult to establish) must be assessed before anesthesia. Evaluation of the cardiac functions and potential anomalies must be assessed. A consultation to a cardiologist might be necessary.

Anesthetic considerations

Requires complete assessment of the neurologic and psychomotor development, family history, and previous problems. The cardiac system should be investigated because of the potential association of congenital ...

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