King-Denborough syndrome: contracture testing and literature review.

The King-Denborough syndrome (KDS) is characterized by dysmorphic features, myopathy, and malignant hyperthermia (MH). Physiologic contracture testing for MH susceptibility has not been reported in KDS. A young boy with KDS underwent muscle biopsy evaluation at age 3 years that documented an abnormal contracture response to halothane, indicating MH susceptibility. Histopathology demonstrated small type II fibers associated with type I hypertrophy. Contracture testing of muscle obtained from the patient's mother was positive, while a sibling's test was negative. This case is the first to demonstrate susceptibility to MH with KDS by using physiologic contracture testing. The presence of positive MH results in both the patient and his mother suggest one of the following: (1) KDS may be part of the spectrum of autosomal dominantly inherited MH; (2) the locus for MH and for KDS may be linked closely and inherited concurrently, or; (3) the association of MH and KDS may be coincidental.