Background: Congenital fiber-type disproportion (CFTD) was first described by Brooke in 1973. CFTD does not seem to be a single pathological entity. Clinical manifestations of CFTD range from mild hypotonia of the
lower limbs to severe respiratory disturbances leading to premature death. The paper presents two children hospitalized due to muscle weakness, facial hypokinesia, rhinolalia, hyperlordosis and inability to close the eyes tightly.
Case Report: Two described children were examined neurologically and the following tests were performed: biochemical analysis of blood, muscle enzyme assay, urinalysis, electromyography and a neuromuscular conduction
test. The quadriceps muscle was biopsied for histological and histochemical examination. The following histochemical stainings were performed: Mallory’s trichrome, succinate dehydrogenase, diaphorase, alkaline and acid ATP-ases, PAS-diastase (glycogen) and Oil red O (lipid). Morphometric analysis was performed by means of a VIDS IV (AMS Cambridge) computerized video image analyzer. Laboratory tests and electromyographic and ultrastructural evaluation of muscle did not reveal any abnormalities. Based on the results of histoenzymatic and morphometric analysis of muscle, we diagnosed mild and progressive variants of congenital fiber-type disproportion (CFTD).
Conclusions: Despite the histopathological, histoenzymatic and ultrastructural images in CFTD myopathy, clinical manifestations may be diametrically different.

Keywords: congenital fiber-type disproportion, myopathy, childhood