19-month-old patient with hypotonia

Index patient presenting with hypotonia, a developmental delay, at the age of 19 months. Bilateral humerus fractures at birth should be noted. He had a previous diagnosis of osteogenesis imperfecta. He had a facial weakness, myopathic face, and involvement of neck flexor muscles with head-lag, and his maximum motor capacity is to sit without support. He is unable to stand on his feet. The following are pictures of the patient: (a) patient at the age of 4 years unable to walk; (b) muscle biopsy at the age of 19 months, demonstrating myopathic changes with increased fatty and fibrous tissue infiltration (HE); (c) central cores (NADH); and (d) index patient carrying a recessive RYR1 mutation; his father carrying a dominant RYR1-malignant hyperthermia susceptibility mutation. (Courtesy of Dr. Goknur Haliloglu.)