Table 2 Muscle biopsy results of individuals reported with biallelic variants in P4HTM.
Current patient | ||||||
---|---|---|---|---|---|---|
Family 1: P1 | Family 2: P2 | Family 3: P5 | Family 5: P13 | |||
Age (Age deceased) | (7 months) | (5 years) | 18 years | (8 years) | (61 years) | |
Age at muscle biopsy (where specified) | 6 months | 2.5 years | – | 8.5 years | 61 years | |
Muscle biopsy | Histology | Mild myopathic changes Significant abnormal variation in fibre size with type 2 predominance and coexpression of fast and slow myosin isoforms. Many fibres expressing neonatal myosin. | Normal histology | Electron microscopy showing increased mitochondria and some with enlarged and abnormal shapes | Increased variability in muscle fibre diameter, hypertrophied muscle fibres, scattered small atrophic fibres, basophilic muscle fibres | (Autopsy specimen) Unspecific type 2 muscle fibre atrophy and COX-negative fibres |
Respiratory chain enzyme testing | Reduced complex I to <30% of control mean Reduced complex IV to 50% of control mean (marginal) Normal complexes II and III | Reduced complex II + III activity to 31% of control | Reduced complexes I–III to 41% of control Reduced complex IV to 38% of control | NR | NR |