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ESSENTIAL HYPERTENSION ANDTHIN BASEMENT MEMBRANE DISEASE

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.

INTRODUCTION

Essential Hypertension (EHT) is rare in children.[1,2] The reported prevalence of mild EHT in the paediatric age group is 1-5%.[1] 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.

CASE REPORT

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
Fig.1 Electron Micrograh (X 150000). Basement membane showing
thinning of the lamina densa. Width of the basement membrane is 125 nm.


DISCUSSION

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.[4] 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.[1] Children with EHT have a strong familial predisposition.[3] Other factors such as salt intake, stress, and obesity have been implicated in the development of EHT.[3]

Secondary hypertension is the most common cause of severe hypertension in children.[1] 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.[3] Another unusual feature of our patient is the severity of the HT. HT is usually only moderately elevated in EHT of childhood.[4]

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.[5] It is regarded to be a benign condition and is a cause of familial benign haematuria.[5] 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.[7] The prognosis in cases with TBMD is good except for persistent haematuria, though progression to chronic renal failure has been reported.[7] 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.

ACKNOWLEDGEMENT

The authors thank Dr. RG Shirahatti - Dean, Seth GS Medical College and KEM Hospital for granting permission to publish this article.

REFERENCES


1.Chantler C. Systemic hypertension. In : Anderson RH, Ma carteny FJ, Shinebourne EA, Tynan M (eds). Paediatric Cardiology 1st edn. Edinburg, Churchill Livingstone. 1987; 2 : 1293-1319.

2.Ingelfinger JR. Hypertension. In : Edelmann CM Jr, Bernstein J, Meadow SR, Spitzer A, Travis LB (eds). Paediatric Kidney Disease. 2nd edn, USA; Little, Brown and Company. 1992; II : 1889-1908.

3.Pruitt AW. Systemic hypertension. In : Nelson WE, Behrman RE, Kliegman RM, Arvin AM (eds). Nelson Textbook of Paediatrics. 15th edn., Bangalore; WB Saunders Company (Prism Books Pvt Ltd). 1996; 1368-74.

4.Ghai OP, Tandon R. Disorders of cardiovascular system. In : Ghai OP (ed). Essential Paediatrics, 4th edn., New Delhi, Interprint. 1996; 212-70.

5.Cosio FG, Falkenhain ME, Sedmak DD. Association of thin basement membrane with other glomerulopathies. Kidney Int 1994; 46 : 471-74.

6.Yoshida K, Suzuki J, Suzuki S, Kume K, Suzuki H, Hujiki T. A case of IgA nephropathy in three sisters with thin basement membrane disease. Am J Nephrol 1998; 18 : 422-24.

7.Saito T, Nishi S, Karasawa R, et al. An ultrastructural study of glomerular basement membrane in rheumatoid arthritis patients with urinary abnormalities. Clin Nephrol 1995; 43 : 360-67.

8.Morita M, White RHR, Raafat F, Barnes JM, Standring DM. Glomerular basement membrane thickness in children. A morphometric study. Paediatr Nephrol 1988; 2 : 190-95.

9.Lanteri M, Wilson D, Savige J. Clinical features in two patients with IgA glomerulonephritis and thin-basement-membrane disease. Nephrol Dial Transplant 1996; 11 : 791-93.

10.McCallum D, Smith L, Harley F, Yiu V. IgA nephropathy and thin basement membrane disease in association with Crohn disease. Paediatr Nephrol 1997; 11 : 637-40.


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