Congenital fiber type disproportion--30 years on.
Thirty years ago, M. H. Brooke coined the term "congenital fiber type disproportion" (CFTD) to describe 12 children who had clinical features of a congenital myopathy and relative type 1 fiber hypotrophy on muscle biopsy. It is now clear that this histological pattern can accompany a wide range of neurological disorders, leading to disillusionment with CFTD as a distinct nosological entity. To determine whether the CFTD has clinical utility as a diagnostic entity, we have reviewed the literature for cases of type 1 fiber hypotrophy and have used strict exclusion criteria to identify 67 cases of CFTD. Most patients presented at birth with weakness and hypotonia, had normal intelligence, and followed a static or improving clinical course. In 43% of families, more than 1 individual was affected. Failure to thrive was common and 25% of patients had contractures or spinal deformities. Bulbar weakness and ophthalmoplegia were less common and cardiac involvement was rare. Twenty-five percent followed a severe course and 10% had died at the time of reporting, all from respiratory failure. Ophthalmoplegia and facial and bulbar weakness were significantly associated with a poorer prognosis. The relatively homogeneous phenotype supports the retention of CFTD as a distinct diagnostic entity and familial occurrence suggests a genetic basis. Regarding the diagnosis of CFTD, we found no strong evidence that the minimum difference between type 1 and type 2 fiber sizes should be increased from 12% to 25%. We also list the other reported causes of relative type 1 fiber hypotrophy to aid their exclusion from CFTD.
Institute for Neuromuscular Research, Children's Hospital at Westmead, Discipline of Paediatrics and Child Health, University of Sydney, Sydney, Australia.
Nigel F
NF
Clarke
Kathryn N
KN
North
D017668:Age of Onset; D005260:Female; D030342:Genetic Diseases, Inborn / Q000150:complications / Q000175:diagnosis; D049673:History, 20th Century; D049674:History, 21st Century; D006801:Humans; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000473:pathology*; D009123:Muscle Hypotonia / Q000145:classification / Q000150:complications* / Q000151:congenital; D018908:Muscle Weakness / Q000151:congenital / Q000209:etiology; D009132:Muscles / Q000473:pathology*; D009134:Muscular Atrophy, Spinal / Q000150:complications / Q000473:pathology; D020914:Myopathies, Structural, Congenital / Q000145:classification / Q000175:diagnosis / Q000209:etiology / Q000266:history; D010523:Peripheral Nervous System Diseases / Q000150:complications / Q000473:pathology