PEDIATRICS Vol. 108 No. 5 November 2001, p. e95
Received Apr 10, 2001; accepted Jun 20, 2001.
, and
From the Departments of * Neurology and Neurological Sciences
and We report a case of congenital hypomyelination
neuropathy presenting at birth. The infant had generalized hypotonia
and weakness. There was decreased respiratory effort along with a right
phrenic nerve and left vocal cord paralyses. Tongue fasciculations were present. Deep tendon reflexes were absent in the upper extremities and
hypoactive (1+) in the lower extremities. Magnetic resonance imaging of
the head revealed no intracranial abnormalities, including normal
cerebral myelination. Nerve conduction study showed absence of motor
and sensory action potentials in the hands when the nerves in the upper
limbs were stimulated. A motor response could be elicited only in the
proximal leg muscles. Needle electromyography study was normal in the
proximal limb muscles, but showed active denervation in the distal
muscles of the arm and leg. These findings were thought to be
consistent with a length-dependent sensorimotor peripheral
polyneuropathy of axonal type with greater denervation of the distal
muscles. A biopsy of the quadriceps muscle showed mild variability in
fiber diameter, but no group typing or group atrophy. The muscle fibers
showed no intrinsic abnormalities. Biopsy of the sural nerve showed
scattered axons with very thin myelin sheaths. There was also a nearly
complete loss of large diameter myelinated fibers. No onion bulb
formations were noted. These findings were thought to be consistent
with congenital hypomyelination neuropathy with a component of
axonopathy. DNA analysis for identification of previously characterized
mutations in the genes MPZ, PMP22, and EGR2 was negative.
Several attempts at extubation failed and the infant became
increasingly ventilator-dependent with increasing episodes of desaturation and hypercapnea. He also developed increasing weakness and
decreased movement of all extremities. He underwent surgery at 2 months
of age for placement of a gastrostomy tube and a tracheostomy. He was
discharged from the hospital on a ventilator at 6 months of age. The
infant was 13 months old at the time of submission of this report.
Although he appears cognitively normal, he remains profoundly hypotonic
and is on a home ventilator. There was no evidence of progressive
weakness.
Congenital hypomyelination neuropathy is a rare form of neonatal
neuropathy that should be considered in the differential diagnosis of a
newborn with profound hypotonia and weakness. It appears to be a
heterogeneous disorder with some of the cases being caused by specific
genetic mutations.
Pediatrics, Stanford University School of Medicine, Lucile
Packard Children's Hospital at Stanford, Stanford, California.
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