Table 3.

Genetic Disorders of Interest in the Differential Diagnosis of Acute Infantile GM2 Activator Deficiency

GeneDiffDx Disorder 1Clinical Features of DiffDx Disorder
Cherry-red macula (≤12 mos)Onset of neurologic regressionOther features / CommentsNot observed in GM2 activator deficiency
ASPA Canavan disease ≤6 mosMacrocephaly, head lag, hypotonia, seizuresLeukoencephalopathy
CLN5
CLN6
CLN8
CTSD
MFSD8
PPT1
TPP1 		Neuronal ceroid lipofuscinoses, infantile & late infantile (OMIM PS256730)≤6 mosVisual deficits, seizuresAbnormal ERG
CTSA Galactosialidosis (OMIM 256540)+<6 mosSeizuresCoarse features, skeletal disease
GALC Krabbe disease ≤6 mosSeizuresLeukodystrophy, peripheral neuropathy, irritability
GBA1 (GBA)Gaucher disease type 2≤6 mosSeizures in some personsOculomotor abnormalities, hypertonia, & opisthotonos; ichthyosiform or collodion skin changes may be seen in persons w/severe involvement.
GFAP Alexander disease, infantile form≤6 mosMacrocephaly, seizuresLeukodystrophy
GLB1 GM1 gangliosidosis type 1 (See GLB1 Disorders.)+≤12 mosSeizuresSkeletal disease
GNPTAB Mucolipidosis II (I-cell disease) (See GNPTAB Disorders.)≤12 mosCoarse facies, hyperplastic gums, skeletal disease; absence of seizures
HEXA Tay-Sachs disease (See HEXA Disorders.)+≤6 mosClinical course nearly identical to GM2 activator deficiency
HEXB Sandhoff disease +≤6 mosClinical course nearly identical to GM2 activator deficiency
NEU1 Sialidosis type II (OMIM 256550)+≤12 mosSeizuresCoarse facies, skeletal abnormalities
SMPD1 Niemann-Pick disease type A (See Acid Sphingomyelinase Deficiency.)+≤12 mosPoor growth, xanthomas, absence of seizures

ERG = electroretinogram

1.

The disorders included in Table 3 are inherited in an autosomal recessive manner, with the exception of Alexander disease, which is inherited in an autosomal dominant manner.

From: GM2 Activator Deficiency

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