Infantile muscle phosphorylase-b-kinase deficiency. A case report.

A Turkish girl is described who showed a severe floppy infant syndrome and respiratory failure at birth. She suffered upper respiratory tract infections and pneumonia. She was ventilated and had hypercapnoea secondary to bradypnoea. Biochemical analysis of skeletal muscle revealed a slightly increased glycogen content, and enzymatic analysis revealed a muscle phosphorylase-b-kinase deficiency. The infant succumbed after 140 days due to persistent apnoea and asystole. Isolated muscle phosphorylase-b-kinase deficiency should be considered as a possible diagnosis in floppy infants.