Congenital fiber type disproportion with fatal outcome: a case report

Autosomal dominant congenital fibre type disproportion: a clinicopathological and imaging study of a large family

Congenital fibre type disproportion (CFTD) is considered a non-progressive or slowly progressive muscle disease with relative smallness of type 1 fibres on pathological examination. Although generally benign, CFTD has a variable natural course and severe progression has been observed in some patients. The pathogenesis of the disorder is unknown and many authors consider CFTD a syndrome with multiple aetiologies rather than a separate clinical entity. A positive family history has been reported in about 40% of cases, but the inheritance pattern is not clear. Both autosomal recessive and dominant modes of inheritance have been suggested. The present paper describes a large, multigenerational kindred that has an inherited myopathy fulfilling the histological criteria of CFTD, with autosomal dominant transmission and high penetrance. The clinical picture, remarkably similar in all affected family members, started in early infancy with mild limb muscle weakness. There was slow progression of symptoms into adulthood, with moderate to severe, mainly proximal, muscle weakness without loss of ambulation. Muscle biopsy from two affected individuals demonstrated predominance of small type 1 muscle fibres without other significant findings. Nerve conduction studies were normal and needle electromyography showed a myopathic pattern. MRI examination performed on three patients from successive generations showed involvement of proximal limb and paraspinal muscles. The clinical and pathological homogeneity in the present family, together with the lack of additional histological abnormalities after decades of disease progression in two affected individuals, supports this being a distinct myopathy with fibre type disproportion. Whether the disease in this family can be regarded as a form of the congenital myopathy known as CFTD or rather a unique condition sharing histological features with CFTD needs further investigation. This is, to our knowledge, the largest kindred with muscle fibre type disproportion reported to date. Our data confirm autosomal dominant inheritance, and this is the first MRI document of this disorder.

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.

Clinical variability of congenital myopathy with type 1 fiber atrophy: a long-term observation of three cases

The variable clinical courses of three cases of congenital fiber type disproportion (CFTD) over a period of 10 years are presented. All showed improvement in early childhood, but subsequently, varying degrees of deterioration were noted: specifically, marked deterioration in case 2 and decreased muscle strength in case 3. Maximal motor function levels were attained differently among the cases. Histological findings included type 1 fiber hypotrophy and increased internal nuclei in common in all cases. Fine structural changes, such as patchy areas of myofibrillar degeneration, were noted in cases 1 and 2 (second biopsy), and cytoplasmic bodies were seen in case 2 (second biopsy). Myotubes were noted in case 3. The degree of cyto-architectural changes did not correlate with clinical severity. The heterogeneity of CFTD is also discussed.

Congenital fiber type disproportion in an adult: a morphometric and microchemical study

A 20-year-old man with marfanoid habitus had a history of congenital hypotonia and muscle weakness. Muscle biopsy showed extreme fiber type disproportion. There was total absence of Type 2B fibers. The severely hypertrophic Type 2A fibers showed twice the normal concentration of creatine phosphate at rest. These advanced morphometric, histochemical and biochemical changes may be interpreted as compensatory phenomena, which may explain the patient's pronounced functional improvement with advancing age.