The detailed clinical features and progress of a child with homozygous 22(I) collagen deficiency are described. Clinically, the disease presents as severe progressive Sillence type IlI osteogenesis imperfecta. The main biochemical defect is the synthesis of an abnormal pro 22(I) chain which does not associate with pro a I(I) chains and therefore is not incorporated into triple helical trimers of type I procollagen which can be used to assemble collagen fibres.

No abstract

Since early infancy, a 15-year-old girl had suffered from an apparently static neuromuscular disorder that chiefly afflicted her proximal muscles but did not spare her distal ones. Her CPK values had repeatedly been mildly elevated and her electromyogram had been considered "myopathic". There were no similar neuromuscular disorders in the family. Quadriceps muscle biopsy showed a type I myofiber predominance of 96%, this girl's muscle disease represented "congenital myopathy with cytoplasmic bodies" as cytoplasmic bodies were recently reported in other sporadic and hereditary neuromuscular disorders of unknown origin.

In a group of 9 healthy newborns, spontaneous activity of different muscles was studied for 6 or 8 hours by means of surface electromyography on the 5th or 6th day of life. According to the local nursing routine the infants were placed in alternating left and right side positions. Averaged EMG activities were analysed with respect to behavioural states and observed postural behaviour. An improved recording technique and the logarithmic presentation of averaged EMG activities allowed the study of characteristics of tonic activity in state 1. The chin muscles showed the most specific EMG pattern in state 1. Chin muscle quiescence was observed during only 15% of that state. Lack of tonic activity was observed more in the beginning than at the end, but never in the middle of state 1. By visual analysis of 41 patterns of averaged EMG activities from the chin muscle it was found that increases of tonic activity only happen stepwise following concomitant phasic activities. Relaxation of tonic activity is either asymptotic or abrupt or by steps. The latter two are especially characteristic for the transition to state 2. Long periods of sustained tonic activity and low motility were characteristic for a long lasting state 1. The interval between the beginning of state 1 and the first increase of tonic activity varied more than the interval between the end of state 1 and the final drop of tonic activity back to the noise level. Other muscles showed less tonic activity in state 1: the neck area (sterncleidomastoid muscle 48% of state 1 time, trapezius m. 32%) was followed by the muscles of the forearm (extensor carpi m. 18%, flexor carpi m. 16%). These muscles also lead the rank order of the modulation of tonic activity. Tonic activity sustained for more than 30 sec. was not observed in state 2, except during transitions. In state 2 as in state 1 the muscles from chin, neck and upper extremities were more active than the muscles from the lower extremities. Durations of activities ranged from 28% (chin) to 13% (ant. tibialis) of state 2 time. No dominance of flexor muscles, which might account for the observed flexed posture, was found. Systematically changed side positions during the recording had no consistent effect on either motility or presence of tonic activity when corresponding muscles from the upper- and the lower-lying body side were compared during state 1. Likewise in state 2 no consistent effect on the total duration of phasic activity was observed. The results are discussed in relation to other known state dependent motor phenomena. It is suggested that sustained tonic activity results from an increased gain of the gamma-loop which may also contribute to the regularity of respiration. Differences between muscles probably reflect maturational and functional differences.

Biopsies from various skeletal muscles were taken post mortem from infants with conceptional ages between 25 and 40 weeks. Cryostat sections were analysed quantitatively. The growth of the mean fibre diameter follows an exponential curve, which is mainly due to an initial predominance of type II-fibres. Before the 34th week of gestation only isolated large "Wohlfart"-fibres show type I staining characteristics. A great number of smaller type I-fibres appear suddenly around the 34th week. Their percentage of the total fibre population increases linearly to 40% at term. The development of the "tonic" type I-fibres correlates with certain aspects of gross motor development. The importance of normal data in the diagnosis of certain congenital myopathies is emphasized.