A Muscle Disorder as Presenting Symptom in a Child with Mucolipidosis IV

Abstract

Psychomotor retardation and hypotonia were found in a 11/2 year old girl with bilateral corneal opacities. Very high levels of enzymes of muscular origin together with abnormal electromyograms and muscle biopsy lead at the time to the diagnosis of an unspecified muscle disorder. Twelve years later mucolipidosis IV (ML IV) was diagnosed in this child. She was then very retarded, ocular and neurologic deterioration were evident and enzyme levels were still very high.
Only few patients affected with ML IV have been reported and all but one were very young; therefore it is important to add observations on the progression of the disease and on unusual clinical features like muscle involvement.

Mucolipidosis type IV (MLIV) is a lysosomal storage disorder which was first described in 1974 (3). The main clinical symptoms are early corneal clouding and psychomotor retardation without visceral involvement or skeletal changes. The disease is rare, inherited as an autosomal recessive disorder and has been mainly described among Jews of Ashkenazi origin (Berman et al 1974, Goutieres et al 1981, Kenyon et al 1979, Kohn et al 1977, Merin et al 1975, Newell et al 1975, Tellez-Nagel et al 1976). The diagnosis is established by the demonstration of granular and lamellar storage material by electron microscopic studies of several tissues including the conjunctiva. Recently Bach et al demonstrated that mucopolysaccharides and gangliosides accumulate in the tissue as a consequence of a partial deficiency of a soluble ganglioside sialidase which is the specific enzymatic defect in the disease (Bach et al 1979).
In the following we describe a girl in whom the presenting symptoms in infancy led to the diagnosis of a primary muscle disorder and in whom MLIV was diagnosed at the age of 13 years.

Key words

Mucolipidosis IV - Muscle hypotonia - Ganglioside sialidase deficiency