Clinical Guidance
Acute infantile GM2 activator deficiency is a neurodegenerative disorder in which infants, who are generally normal at birth, have progressive weakness and slowing of developmental progress between ages four and 12 months. An ensuing developmental plateau is followed by progressively rapid developmental regression. By the second year of life decerebrate posturing, difficulty in swallowing, and worsening seizures lead to an unresponsive vegetative state. Death usually occurs between ages two and three years. To date, 13 individuals have been reported with acute infantile GM2 activator deficiency [, , , , , , , , , , , ]. The following description of the phenotypic features associated with acute infantile GM2 activator deficiency is based on these reports. Table 2. Acute Infantile GM2 Activator Deficiency: Frequency of Select Features
Feature | # of Personsw/Feature | Comment |
|---|
Developmental delay | 13 | — |
Cherry-red macula | 13 | — |
Hypotonia | 12 | Tone not specifically discussed in 13th case is likely present in all affected persons. While axial tone is universally , limb tone may be or . |
Seizures | 9 | — |
Exaggerated startle response | 8 | — |
Hyperreflexia | 4 | Hyperreflexia was present in all reports in which reflexes were specifically discussed. |
Hepatomegaly | 2 | Affected infants are generally normal at birth. Progressive weakness, exaggerated startle, and slowing of developmental progress is typically noted between ages four to 12 months. |
Source: GeneReviews — "GM2 Activator Deficiency"
