20 10.20.
Diagnosis
over the patient’s medical records, as
was her practice, to try to get a sense of
what might be going on. In reviewing
the man’s chart, she noticed that in addi-
tion to eos in his skin, the patient had
an overabundance of eos in his blood
— more than three times the number
normally seen in circulating blood. Aller-
gies didn’t cause those kinds of numbers.
What, then, could cause that kind of cell
to proliferate?
Generally, the No. 1 job of eos in
the body is to fi ght off parasites. In the
United States, one of the most common
parasites is toxocara, which is transmit-
ted from the feces of infected dogs and
cats. Strongyloides, another parasite, has
been found in people who have spent
time in tropical or subtropical regions
where it is endemic. Both can cause a
rash like this, so either was possible.
More concerning in a patient at this
age was a malignancy or a syndrome of
hypereosinophilia — a disorder in which
this type of white blood cell begins to
proliferate wildly.
↓
Beware Dogs and Cats
She saw the man early the next day. He
was chatty, but even as he told his story,
he could not stop scratching. It turned
out that he had had a cat that was old and
sick, and his half brother had two dogs
and four cats that he’d recently spent
time with. So toxocariasis certainly was
possible. He had visited the Caribbean
many times — though not recently. Still,
that meant strongyloidiasis was also a
potential culprit. Besides the itch and
the sleep deprivation it caused, he had
no other complaints.
On examination, the man’s body was
covered with well-defi ned red infl amed
patches on his chest, back, buttocks
and thighs that were crisscrossed with
scratch marks. In some areas the skin
was thick, leathery and lumpy from the
rash and the skin’s response to per-
sistent scratching or rubbing. Other
areas were covered with tiny fl akes of
scaling skin.
When the patient was dressed, Iam-
matteo returned to the examination
room. She didn’t think this was an aller-
gy, she told him. But it could be a para-
site. She thought it was more likely toxo-
cara, given his recent exposures to dogs
and cats. Toxocara is a type of parasite
called a nematode or roundworm. It lives
in the gastrointestinal tract of dogs and
cats. Until the end of the 20th century,
visceral toxocariasis could be diagnosed
only by the symptoms it caused when it
invaded the organs of the body — the
liver, the lungs, the brain or the eyes.
These were serious infections — causing
everything from wheezing and shortness
of breath to blindness or, rarely, death. It
wasn’t until a diagnostic blood test was
developed that other manifestations of
the disease were identifi ed. In what’s
called common toxocariasis, patients
have gastrointestinal symptoms as well
as an itchy rash. In covert toxocariasis,
the only symptom is an itchy rash. These
infections often resolve on their own
over time, but they can also be treated
with a medicine. This patient could have
covert toxocariasis.↓
Narrowing Things Down
Iammatteo said she would test for both
toxocariasis and strongyloidiasis. She
would also refer him to a hematologist
to look for a malignancy or other trigger
that might have caused his overprolifer-
ation of white blood cells. There were
other causes of his rash and eosinophil-
ia, but these were the most likely and a
good place to start.
A few days later, she got a possi-
ble answer and called the patient. Youprobably have toxocariasis, she told him.
The blood test came back positive, but
she explained there was a caveat. The
test measures whether the immune sys-
tem has responded to this particular par-
asite — ever. The fact that it was positive
meant that the patient had been exposed
to the parasite, but it couldn’t determine
when the exposure occurred. Toxocara
infections are most common in children.
But the test will still be positive even if
the infection is long gone. The only way
to know for certain that the toxocara
was causing the itch, she told him, was
to treat him and see how he responded.
She referred him to an infectious-disease
doctor who prescribed the recommend-
ed fi ve days of Albendazole.
Because he couldn’t know for sure if
this was the right diagnosis, the patient
kept his appointment with the hematol-
ogist. That doctor sent off more blood to
look for signs that the overabundance of
these cells could be caused by an eosin-
ophil gone wild.↓
Relief at Last
But well before those tests results came
back negative, the patient felt that he
had his answer. Within days of com-
pleting his treatment with Albendazole,
the itching resolved. And by the time
he went back to see Iammatteo two
weeks later, even the rash had mostly
disappeared.
Why had Iammatteo been able to
figure this out when other doctors
couldn’t? the patient asked when he saw
her for a follow-up visit. She explained
that she’d gone to Albert Einstein Col-
lege of Medicine in the Bronx, and one
professor there was an expert in parasi-
tology. She took her class, and what she
learned stuck with her. Diff erent med-
ical schools have diff erent strengths,
she told me later. Parasites were one
of theirs.
And, she added, doctors are taught
that toxocara infection is rare. But now
she’s not so sure. Since making this
patient’s diagnosis last spring, she told
me she has diagnosed nearly a dozen
cases of toxocariasis in patients whom
she might not have thought to test for
the parasite if not for this older man and
his rash. ‘‘I know I’ve been successfully
diagnosing more of it because it’s on
my mind.’’Photo illustration by Ina JangLisa Sanders, M.D.,
is a contributing
writer for the magazine.
Her latest book,
‘‘Diagnosis: Solving the
Most Baffl ing Medical
Mysteries,’’ was published
by Crown in August.
If you have a solved case
to share with Dr.
Sanders, write her at
Lisa.Sandersmd@
gmail.com.