A 26-year-old man had proximal weakness in the shoulder and the pelvic girdle since infancy. His sister, aged 16 years, presented a similar phenotype with more pronounced pelvic weakness. His muscle biopsy showed dense non-reducing inclusions which had a lamellar pattern at the ultrastructural level. These structures showed the typical features of fingerprint inclusions which were widely distributed in the fibers. Several central cores and other structural changes such as Z-line streaming were also observed. In view of the central cores, the male patient was investigated for malignant hyperthermia susceptibility. After exposure to halothane or caffeine, unusual intense contractures were observed on fiber preparations. The coexistence of central cores associated with fingerprint inclusions is suggestive of mixed congenital myopathy, which is in our case associated with malignant hyperthermia susceptibility.