AJR 2004; 182:830-831
© American Roentgen Ray Society
Pulmonary and Lower Extremity Vascular Lesions in a Patient with Homocystinuria: Radiologic Findings
Eijun Sueyoshi,
Ichiro Sakamoto,
Kazuto Ashizawa and
Kuniaki Hayashi
Nagasaki University School of Medicine Nagasaki 852-8501,
Japan
Homocysteine is an important contributing factor in thrombus formation,
vascular injury, and vascular disease
[1–3].
Herein, we report the radiologic findings of homocysteine-induced pulmonary
and lower extremity vascular disease.
A 21-year-old man was admitted to our hospital with a 3-year history of
intermittent claudication. Arteriography of the lower extremities showed
stenosis of both external iliac arteries
(Fig. 4A). Venography of the
lower extremities showed thrombus in the left popliteal vein and development
of collateral vessels (Fig.
4B). Initially, the patient was treated with urokinase and
antiplatelet agents. Thirteen days after admission, he complained of chest
pain and dyspnea. A pulmonary perfusion scintigram revealed multiple perfusion
defects in both lungs, and the diagnosis of pulmonary embolism was made. After
treatment with urokinase and antiplatelet agents, the symptoms of pulmonary
embolism gradually subsided.
In view of the patient's young age, hypercoagulability, and clinical
history, homocystinuria was strongly suspected. A nitroprusside urine test was
positive, and the blood and urine examinations showed elevation of
homocysteine level. Enzyme assay revealed that percutaneously obtained liver
cells had a low activity of cystathionine ß-synthase. However, after
addition of vitamin B6, the activity of cystathionine
ß-synthase recovered. The diagnosis of homocystinuria was thus
confirmed.
After the patient underwent treatment with vitamin B6, his
coagulability and homocysteine level of blood and urine returned to normal.
The patient was discharged and treated with a supplement of vitamin
B6 as an outpatient. He had remained symptom-free after discharge,
and follow-up arteriography and venography of the lower extremities showed no
abnormality. However, imaging studies of the lung showed a gradual increase in
size of segmental branches of the pulmonary arteries (Figs.
4C and
4D). Pulmonary
ventilation–perfusion scintigrams showed multiple newly developed
mismatched defects in both lungs. Fortunately, there have been no symptoms
related to chronic pulmonary embolism. His pulmonary arterial systolic
pressure has slightly increased, but remained below 90 mm Hg during the
follow-up period. The patient is still doing well after 25 years of
follow-up.
Homocystinuria should be considered in patients in their third decade or
younger who develop arterial and venous thrombotic events
[1]. In our patient, various
vascular diseases such as stenosis of both external iliac arteries, thrombosis
of the left popliteal vein, chronic pulmonary embolism, and aneurysmal
dilatation of the pulmonary arteries were present. There are several
mechanisms through which homocystinuria is thought to cause vascular disease.
Abnormalities of platelets, vascular endothelium, soluble factors involved in
blood coagulation, or possibly even lipoproteins may be contributory.
Homocysteine also has cytotoxic effects on vascular endothelium with resultant
intimal thickening, lipid-laden macrophages, and smooth-muscle cell
proliferation [1,
3].
In our patient, coagulability and the homocysteine level of blood and urine
returned to normal limits after treatment with vitamin B6. However,
the pulmonary arteries gradually increased in size during the follow-up
period. Pulmonary endothelial damage by homocysteine is thought to have
initially caused pulmonary thrombosis, which induced pulmonary hypertension at
an early stage. After that, pulmonary hypertension might have formed
additional vascular damage. Both increasing pressure and pulmonary endothelial
damage may have contributed to progressive dilatation of pulmonary arteries
[4]. Therefore, careful
follow-up studies are needed, even if thrombotic symptoms and laboratory data
are unremarkable after medical treatment.
References
- Lobo CA, Millward SF. Homocystinuria: a cause of hypercoagulability
that may be unrecognized. J Vasc Interv Radiol1998; 9:971
–975[Medline]
- Rodgers GM, Chandler WL. Laboratory and clinical aspects of
inherited thrombotic disorders. Am J Hematol1992; 41:113
–122[Medline]
- Rees MM, Rodgers GM. Homocysteinemia: association of a metabolic
disorder with vascular disease and thrombosis. Thromb
Res 1993;71:337
–359[Medline]
- Bartter T, Irwin RS, Nash G. Aneurysms of the pulmonary arteries.
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