Sialidosis

At a glance

Agenetic neurodegenerative disease (oligosaccharidosis) caused by a deficiency in α-N-acetyl neuraminidase (or sialidase) leading to excessive tissue sialyloligosaccharides (sialylated oligosaccharides) in nerve cells.

Synonyms

Cherry-Red-Spot-Myoclonus Syndrome; Mucolipidosis Type I; Sialidase Deficiency; Glycoprotein Neuraminidase Deficiency; NEUG Deficiency; Lipomucopolysaccharidosis.

Classification

It is divided into two clinical types:

• Sialidosis Type I: Cherry-Red-Spot, Myoclonus Syndrome (less severe)

• Sialidosis Type II: Mucolipidosis Type I; Sialidase Deficiency; Glycoprotein Neuraminidase Deficiency; NEUG Deficiency; Lipomucopolysaccharidosis. (congenital and infantile forms)

Incidence

Genetic disorder with a 2.5:1 male preponderance. The majority of Type I patients have been Italian.

Genetic inheritance

Autosomal recessive.

Pathophysiology

The lysosomal sialidase gene (NEU1) has been mapped to chromosome 6 (6p21.3). The enzyme lysosomal neuraminidase (sialidase) normally removes the terminal sialyl linkages of several oligosaccharides and glycoproteins. Its deficiency results in excessive accumulation of complex sugars rich in sialic acid.

Diagnosis

Excessive urinary oligosaccharides can be demonstrated. Definitive diagnosis is based on sialidase activity present in tissue samples (eg, fibroblasts, white blood cells [WBCs]). Prenatal diagnosis (amniotic fluid cells) is possible.

Clinical aspects

Clinically, sialidosis can have four forms, which consists of:

• Type I (Mild Form): Presents with a cherry-red spot (macula) and myoclonus phenotype that is usually associated with isolated neuraminidase deficiency. Nystagmus, ataxia, and seizures are reported. Usually second decade of life.

• Type II (Severe Form): Abnormal somatic features including coarse faces, broad nasal root, thick lips, deafness, delayed bone age, pectus carinatum, scoliosis, short rib cage, and dysostosis multiplex. Other clinical features include lipidosis, sulfatidosis, macular pigmentary abnormality, movement disorder, dwarfism, speech defect, splenomegaly and storage liver disease.

• Congenital Form: Results in hydrops fetalis, hepatomegaly, and premature death.

• Infantile Form: Resembles Hurler Syndrome.

Precautions before anesthesia

Chest radiographs and resting oxygen saturation must be obtained in view of frequent respiratory infections/obstructive sleep apnea. Abnormal airway with macroglossia, thickened mucosal folds in oro- and naso-pharynx, together with skeletal deformities. Liver function tests and coagulation profiles if hepatomegaly is present.

Anesthetic considerations

Airway management will be a major challenge with or without endotracheal intubation. Loss of muscle tone after general anesthesia induction results in upper airway obstruction. It is recommended to have a laryngeal mask airway available in case of failure to ventilate with face mask or intubate the trachea. Patient positioning in the presence of contractures can be difficult. Chronic pulmonary infections and kyphoscoliosis can lead to postoperative respiratory failure.

Pharmacological implications

Avoid the use of muscle relaxants if possible until the trachea is intubated ...