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European Journal of General Medicine
Medical Investigations Society
ISSN: 1304-3897
Vol. 2, Num. 1, 2005, pp. 39-40
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European Journal of General Medicine, Vol. 2, No. 1, 2005, pp. 39-40
POLYCYSTIC KIDNEY DISEASE WITH HIGHLY ELEVATED γ-GLUTAMYL
TRANSPEPTIDASE
İlker Taşçı1, Fatih Bulucu1,
Mehmet Refik Mas1, Samet Verim2
Gülhane School of Medicine, Departments of Internal Medicine1 and
Radiology2 Ankara, Turkey
Correspondence: Dr. Ilker Tasçı Asker Hastanesi,
Tatvan 13200, Bitlis, Turkey Phone : +90 532 2861897 Fax :
+90 434 8273426 E-mail :ilkertasci@yahoo.com
Code Number: gm05009
Patients with polycystic kidney disease (PKD) may be asymptomatic
until the later ages owing to the underlying disorder. A renal proximal tubule
associated
enzyme, γ-glutamyl transpeptidase (γ-GT),
was reported to be normal in PKD. We report an elderly case with highly elevated γ-GT
with no other potential source.
Key words: Polycystic kidney disease, gamma glutamyl transpeptidase,
elderly
INTRODUCTION
Polycystic kidney disease (PKD) is characterized by the growth of multiple
cysts in the kidneys. Autosomal dominant, the most common form that develops
between the ages of 30 and 40, and autosomal recessive PKD, which begins early
in life, are the inherited types (1).
γ-glutamyl transpeptidase (γ-GT) is a membrane-bound enzyme that
is an integral part of the γ-glutamyl cycle functioning in the degradation
and neo-synthesis of glutathione in the kidney (2,3). It is primarily synthesized
in the brush border membrane of proximal tubules (4), but is present in cell
membranes in pancreas, liver, spleen, heart, brain, seminal vesicles and endothelium
(5-7).
CASE
A-74 year old man was admitted to our hospital with a clinical picture of fatigue
and vertigo for 20 days. In his history, there was only rarely seen dark urine.
He had no history of alcohol use, chronic hepatic or renal disease, and drug
intake. The physical examination was normal. CBC and CRP were normal, erythrocyte
sedimentation rate was 33 mm/hour, and RF was negative. Serial urine analyses
were normal. In detailed blood chemistry, the only abnormal finding was γ-GT
of 334 U/L (normal range 7-50 U/L), which persisted over the following days.
Liver function tests, cholestatic markers and renal function tests were normal
(AST: 25 U/L, ALT: 32 U/L, ALP: 225 U/L, Total Blb: 1,0 mg/dL, Urea: 25 mg/dL,
Cr: 1,1 mg/dL). Estimated GFR was 65 ml/min. In abdominal ultrasonography the
only pathological finding was enlargement and multiple cysts in both kidneys.
Thoracoabdominopelvic CT showed only polycystic renal disease with no enlargement
in intra or extrahepatic bile ducts. Cranial CT revealed only slight age related
changes. The patient was treated for his vertigo and improved satisfactorily
before discharge. In outpatient follow-up, there was no decline in serum γ-GT
levels in the following months (666, 276 and 336 U/L).
DISCUSSION
The cysts in polycystic kidney disease originate as expansions of renal tubules.
Cysts arise in every tubule segments in autosomal dominant type whereas they
are derived from collecting tubules in autosomal recessive type (8). Although γ-GT
synthesis occurs mainly in the kidneys, elevated γ-GT is interestingly
not common in patients with cystic renal disease. The reason for this is not
so clear but it may theoretically be related to the pathophysiological mechanisms
that cysts derived from tubules rapidly close off from the original nephron
after formation, but retain their functional capacity and show similarity with
hepatic cysts (9). No significant difference was found in serum and urine γ-GT
activity in 32 patients with PKD when compared to patients with renal plus
hepatic cysts and healthy controls (10). For our patient, who had no symptom
even until he was 74 years old, we have found no pathology in the liver, intestine,
pancreas etc. that might possibly be source of elevated γ-GT. Such an
increase in γ-GT in an accidentally diagnosed PKD patient may suggests
that the cysts not always close off from the nephron and subsequently may drain
into venous system, though it is quite hard to get any direct evidence. Finally,
renal cystic disease may be a reason of elevated γ-GT levels of unknown
origin, and if the liver and the biliary tree are normal, should clinically
be suspected more frequently.
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