Carnitine palmitoyltransferase II deficiency is the most common inherited lipid-metabolism disorder in skeletal muscle.
The adult form causes exercise-induced myalgias, myoglobinuria with rhabdomyolysis and myopathy. Other triggers include fever, illness, and a high-fat dietary load.
Laboratory findings include low serum carnitine levels (both total and free), elevated CK (especially after exercise episodes), and myoglobinuria.
CPT II deficiency has an autosomal recessive inheritance pattern.
Muscle biopsy shows vacuoles on H&E stain and increased granular staining at the periphery of muscle fibers on trichrome stain. Most telling, however, is a positive
Red-oil-O stain (staining for lipids) as shown below.
Images courtesy of Dr. Lei Zhao, Dr. Jerry Wong, and Dr. Peter Pytel at the University of Chicago.