Pediatrics Answers 429consistent with either of those in that there is sensory preservation. A deep
muscle biopsy (b)is considered in cases of persistent, progressive muscle
weakness that would not be indicated with this history. It is most helpful in
diagnosing severe inflammatory or autoimmune myopathies. Hypokalemia
(c)can be associated with weakness, but is global and not localized to
lower extremities as in this case, so electrolytes are not likely to be helpful
in coming to a diagnosis. The edrophonium challenge (e)is a test used to
diagnose myasthenia gravis, an autoimmune condition in which antibodies
block the receptor for acetylcholine on the synaptic junction causing easy
fatigability. Deep tendon reflexes are typically preserved. Edrophonium
blocks the breakdown of acetylcholinesterase which can temporarily resolve
the symptoms and is diagnostic for this condition.
386.The answer is c.(Fleischer and Ludwig, pp 775-776, 840.)This is a
classic case of infant botulismcharacterized by generalized weakness,
pupillary unresponsiveness, and hypoventilation. Patients often present
with an initial complaint of constipation. They are noted to have a particu-
larly weak cry. The condition is caused by release of the botulinum toxin
from Clostridium botulinum. The toxin prevents release of acetylcholine
from the neuromuscular junction. Older children present with complaints
of diplopia, dysarthria, and dysphagia. Young infants are particularly sus-
ceptible from ingestion of honey,which can harbor C botulinumspores.
The pH in infant’s stomachs does not destroy the spores. Therefore, honey
is not recommended for any infant under 1 year of age.
This is not a case of spinal muscular atrophy (ie, Werdnig-Hoffman dis-
ease) (a),which is an autosomal recessive disorder characterized by muscle
weakness that can affect every aspect of eating, breathing, and moving and
will often be apparent from very early on—even before the age of this child.
Brain tumors (b)can cause some of these symptoms, but would not typi-
cally present with generalized weakness and poorly responsive pupils. This
child doesn’t show particular signs of increased intracranial pressure like
vomiting or persistent irritability. Similarly, this patient is not showing signs
of meningitis (d).She is afebrile and is not irritable. Organophosphate poi-
soning(e)causes increased muscarinic and nicotinic tone from the inhibi-
tion of acetylcholinesterase. The symptoms may be similar to this patient
with drooling and weakness. In addition diarrhea, autonomic dysfunction,
and CNS disturbances are common. This condition is unlikely in a nonmo-
bile infant and exposures are uncommon in this setting.