ESSENTIAL HYPERTENSION ANDTHIN BASEMENT
MILIND S TULLU*, MADHUMITA TRIPATHI**, SHAILA R KHUBCHANDANI+,JAISHREE R KAMAT***,
RAJWANTI K VASWANI****
*Lecturer; **Resident Medical Officer; ***Professor and Head of Department;
****Associate Professor, Department of Paediatrics Seth GS Medical College
and KEM Hospital, Parel, Mumbai 400 012, Maharashtra, India. +Consultant Histopathologist,
Department of Histopathology and Electron Microscopy, Jaslok Hospital and
Research Centre, 15, Dr. G Deshmukh Marg, Mumbai 400 026, Maharashtra, India.
Essential hypertension is uncommon in
childhood. A one-and-half-year-old female child was detected to have hypertension.
Detailed investigations failed to detect any secondary cause for the hypertension.
The kidney biopsy of the child showed thin basement membrane on electron microscopic
examination. The child has been diagnosed as a case of essential hypertension
associated with thin basement membrane disease.
Essential Hypertension (EHT) is rare in children.[1,2] The
reported prevalence of mild EHT in the paediatric age group is 1-5%.
Thin Basement Membrane Disease (TBMD) is also a rare entity. Though TBMD has
been reported to co-exist with other glomerular abnormalities or as an isolated
anomaly, its significance in causing a renal disease is not known. We report
an interesting case of EHT in a toddler who also had TBMD on renal biopsy.
A one-and-half-year-old female child born of a non-consangineous marriage was
brought to our hospital in January 2000 with the history of puffiness of face,
oedema feet and oliguria. There was no history of haematuria, vomiting, headache,
convulsion, or drug ingestion. There was no family history of hypertension (HT).
On general examination, the child had normal heart rate and respiratory rate.
She had elevated blood pressure (146/90 mm Hg in both the upper limbs). The
blood pressure in the lower limbs was 10 mm higher than the upper limbs. She
had periorbital oedema and oedema of the feet. The fundus examination did not
show hypertensive changes. Rest of the systemic examination was normal.
Investigations revealed normal haemogram, renal chemistry, liver function tests
(including serum protein level), and complement (C3) levels. The urine examination
did not reveal proteinuria or haematuria and the urine culture was negative.
The ultrasonography of the abdomen was normal and ANA and anti-dsDNA tests were
negative. Her HT responded to frusemide therapy.
The child was readmitted in March 2000 with similar complaints including HT
which was treated by adding nifedipine to frusemide. An intravenous urography
and the micturating cystourethrography was normal. No abnormality was detected
on the abdominal aortogram with bilateral renal angiogram. The kidney biopsy
showed a normal histology on light microscopic examination and thin basement
membrane disease on the electron microscopic (EM) examination, the width of
the basement membrane being 125 nm (Fig. 1). On EM examination, features of
Alportís syndrome (like splitting and Ďbasket-weav ingí appearance of the glomerular
basement membrane) were absent. Repeated urine examinations failed to document
any haematuria or proteinuria. The parentís urine did not reveal haematuria.
The DMSA and DTPA renal scans, electrocardiogram, and colour doppler study of
the heart were normal. The urine vanillylmandelic acid (VMA) level was insignificantly
elevated (patientís value : 15.1 mg/gm creatinine; normal : 1-10 mg/gm creatinine).
A repeat VMA level after one month was normal (patientís value : 1 mg/24 hrs;
normal : 1-8 mg/24 hrs). CT scan of the abdomen revealed normal adrenal glands.
The urinary metanephrine level was also normal (patientís value : 0.11 mg/24
hrs; normal : upto 0.9 mg/24 hrs). Since May 2000 to date, a third antihypertensive
(prazosin) has controlled the HT.
|Fig.1 Electron Micrograh (X 150000).
Basement membane showing
thinning of the lamina densa. Width of the basement membrane is 125 nm.
Essential Hypertension (EHT) is more common in adolescents than in younger children.[2,3]
Children destined to develop EHT as adults belong to the group which is around
90th percentile or above as indicated by tracking studies.
While a value exceeding the 95th percentile for an adolescent may be regarded
as abnormal (> 140/90 mm Hg), a reading of systolic and/or diastolic blood
pressure higher by at least 15 mm Hg persistently above the 95th percentile
categorizes a child as severe HT. Children with EHT have
a strong familial predisposition. Other factors such as
salt intake, stress, and obesity have been implicated in the development of
Secondary hypertension is the most common cause of severe hypertension in children.
These secondary causes (like renal, vascular and endocrine causes) have to be
ruled out to label a patient as having EHT. The investigations done for chronic
renal disorders (pyelonephritis, glomerulonephritis), structural renal disorders,
vesicoureteral reflux, systemic lupus erythematosus, coarctation of aorta, renal
arterial lesions and phaeochromocytoma were normal in our patient. She had HT
without any apparent cause and therefore has been labelled as EHT. However,
despite detailed investigations, her oedema cannot be accounted for. It is uncommon
to make a diagnosis of EHT in children younger than 10 years of age.
Another unusual feature of our patient is the severity of the HT. HT is usually
only moderately elevated in EHT of childhood.
Thin glomerular basement membrane nephropathy or thin basement membrane disease
(TBMD) is an autosomal dominant disease characterized by the presence of abnormal
thinning of the glomerular basement membrane. It is regarded
to be a benign condition and is a cause of familial benign haematuria.
We could not document haematuria in our patient or her parents. Thin glomerular
basement membrane is present in 5-10% of normal kidneys (from transplant donors).[5-7]
It is also seen in other hereditary renal diseases like the Alportís syndrome,
IgA nephropathy, mesangial proliferative glomerulonephritis, and in patients
with acquired glomerular diseases.[5,6,8,9] Clinical features
and EM examination of the kidney biopsy ruled out the presence of these renal
disorders in our patient. The diagnosis of TBMD is based on the demonstration
of average width of the glomerular basement membrane of less than 200-250 nm.[5,6]
Interestingly, thinning of the basement membrane has also been observed in patients
with rheumatoid arthritis on gold sodium thiomalate therapy.
The prognosis in cases with TBMD is good except for persistent haematuria, though
progression to chronic renal failure has been reported.
McCallum et al have reported a female child with TBMD, IgA nephropathy, and
Crohnís disease and a male child with TBMD and Crohnís disease.10 The presence
of TBMD in our patient may just be an incidental finding and not an aetiological
one. This case has been reported for the uncommon association of EHT and TBMD.
The authors thank Dr. RG Shirahatti - Dean, Seth GS Medical College and KEM
Hospital for granting permission to publish this article.
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