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The myopathology of floppy and hypotonic infants in Singapore
Mapalagama K Premasiri1, Yoke-Sun Lee
1Department of Pathology, National University of Singapore.
Insights
Spinal muscular atrophy and congenital muscular dystrophy are leading causes of floppy infants in Singapore. Many cases showed no significant pathology, requiring further investigation into infant hypotonia.
Area of Science:
- Neurology
- Pediatrics
- Pathology
Background:
- Floppy or hypotonic infants present a diagnostic challenge.
- Identifying the underlying muscle disease is crucial for management.
Purpose of the Study:
- To determine the types and frequency of muscle diseases in hypotonic infants in Singapore.
- To analyze muscle biopsy findings in a cohort of floppy infants.
Main Methods:
- Retrospective review of 80 muscle biopsies from infants with floppy/hypotonic presentation.
- Biopsies were performed between 1978 and 2000.
- Analysis included light microscopy, histochemistry, and ultrastructural examination.
Main Results:
- Spinal muscular atrophy was the most common diagnosis (33%).
- Congenital muscular dystrophy occurred in 13% of cases.
- Congenital myopathies and metabolic myopathies (e.g., Pompe disease) were also identified.
- A significant proportion (29%) of biopsies showed no significant pathological findings.
Conclusions:
- A diverse range of muscle pathologies contribute to infant hypotonia.
- Spinal muscular atrophy and congenital muscular dystrophy are key diagnoses.
- The high rate of unclassified pathology necessitates further research into the etiology of floppy infants.
Aims:
This study attempts to determine the type and relative frequency of muscle diseases contributing to floppy and hypotonic infants in Singapore.
Methods:
Eighty consecutive muscle biopsies in the Department of Pathology, National University of Singapore, in the period 1978-2000, in which a clinical diagnosis of floppy or hypotonic infant was made, were reviewed.
Results:
The commonest cause of severe hypotonia in infancy was spinal muscular atrophy, which accounted for 33% of cases followed by congenital muscular dystrophy (13%). Eight cases (10%) of infantile type II glycogenosis (Pompe's disease) were encountered. There were seven cases of congenital myopathy, of which four were centronuclear myopathy, and one each of central core myopathy, nemaline myopathy and congenital fibre type disproportion. One case of centronuclear myopathy was associated with type I fibre smallness. Type II atrophy, which is generally considered a non-specific change, was encountered in five cases. Of interest is the relatively large number of muscle biopsies (29%) in which no significant pathological features were encountered at the light microscopic, histochemical as well as ultra-structural level.
Conclusions:
The study has revealed a great variety of pathology affecting the muscle of children presenting as floppy infants or with hypotonia. The muscle diseases included spinal muscular atrophy, congenital muscular dystrophies, congenital myopathies and metabolic myopathies. However, 23 (29%) cases showed no significant pathology. For this group of floppy and hypotonic infants further studies are needed.
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