Lipoprotein lipase deficiency.KN Shankar, HS Bava, J Shetty, MK Joshi
Department of Paediatrics, Seth G.S. Medical College, Parel, Mumbai.
Correspondence Address: Source of Support: None, Conflict of Interest: None PMID: 0010740731
Source of Support: None, Conflict of Interest: None
A rare case of a 3 month old child with lipoprotein lipase deficiency who presented with bronchopneumonia is reported. After noticing lipaemic serum and lipaemia retinalis, a diagnosis of hyperlipoproteinaemia was considered. Lipoprotein lipase deficiency was confirmed with post heparin lipoprotein lipase enzyme activity estimation.
Keywords: Case Report, Consanguinity, Human, Infant, Lipids, blood,Lipoprotein Lipase, deficiency,Male,
Lipoprotein lipase deficiency is an extremely rare type of hyperlipoproteinaemia characterised by massive accumulation of chylomicrons in plasma. This disorder is often diagnosed accidentally when lipaemic serum is noticed. Lipaemia retinalis or creamy white retinal vessels on fundoscopy is a unique feature of this disorder see [Figure - 1].
A 3 month old boy born of a 3rd degree consanguinous marriage was admitted with a history of fever and non-productive cough for 15 days and breathlessness for 1 day prior to admission. He also had asymptomatic skin lesions noticed since 1 month. He was breastfed with supplemental buffalo milk. An elder sibling and mother were normal.
On examination, the child weighed 5.5 kg and was pale, irritable, febrile and tachypneic. Chest revealed bilateral scattered rales and rhonchi. Small 3-5 mm skin nodules were noticed in clusters over the nape of the neck and also scattered over the body. A clinical diagnosis of bronchopneumonia was made and during blood collection lipaemic serum was noted. Subsequently a typical fundal picture of lipaemia retinalis was noticed.
Investigations revealed Hb of 3.9 g/dl, total count of 13,200 with 82% polymorphs and 18% lymphocytes and a reticulocyte count of 12%. Chest X-ray showed hilar lymphadenopathy and bronchopneumonic changes. Lipid profile in 1/3 dilutions revealed cholesterol of 200 mg/dl and triglycerides of 1212 mg/dl with a cholesterol to triglyceride ratio of 0.16. Serum sodium was low at 123 mEq/1. The lipaemic serum persisted even after keeping the child nil orally for 5 days.
Post heparin lipoprotein lipase activity was 0.117 mEq of free fatty acids/ml/min (N-0.291 + 0.016) and gel electrophoresis demonstrated the presence of apoprotein C II. Skin biopsy revealed cutaneous xanthoma. Secondary hyperlipoproteinaemias due to hypothyroidism, diabetes and lupus were ruled out. As the reticulocyte count was high, Hb electrophoresis was carried out but fetal Hb was only 6.6%.
Infection was controlled with antibiotics and child was kept on a fat free diet. Repeat lipid profile after 15 days revealed cholesterol of 318 mg/dl and triglycerides of 472 mg/dl (undiluted serum). Fundus became normal and the cutaneous xanthomas appeared to be disappearing. Lipid profile of the elder sibling and mother were normal.
Lipoprotein lipase deficiency is an extremely rare autosomal recessive disorder with an incidence of less than one in one million. The enzyme lipoprotein lipase is present on the luminal surface of vascular endothelium and hydrolyses chylomicrons into glycerol and free fatty acids hence chylomicrons massively accumulate in plasma with deficiency. The enzyme activity is assayed after heparin infusion since heparin releases the enzyme from vascular endothelium. Recent research into molecular genetics have identified several point mutations in the lipoprotein lipase gene. A single aminoacid substitution from Glycine to Glutamine at position 142 has been shown to abolish the enzymatic activity of lipoprotein lipase.
The disorder is clinically salient though the enzyme is deficient from birth and most cases are accidently diagnosed. Infection is a common precipitating factor. Clinical manifestations include eruptive cutaneous xanthomas, recurrent bouts of pancreatitis, episodic abdominal pain, lipaemia retinalis and mild hepatosplenomegaly. Accelerated atherosclerosis is not observed.
The main clue to the diagnosis is persistence of lipaemic serum after 12 hours of fasting. Lipid profile shows elevated cholesterol (160-400) and triglycerides (1500-4500) with a cholesterol: triglyceride ratio of less than 0.2. The diagnosis becomes questionable if the ratio is above 0.2 and unlikely if it approaches 0.5. The diagnosis is confirmed by absent or very low lipoprotein lipase activity from post heparin plasma and demonstration of apoprotein C II by gel electrophoresis.
Management is mainly by dietary fat restriction to less than 10 g/day. Increased carbohydrates and proteins are necessary to provide adequate calories. Medium Chain Triglycerides are helpful because their hydrolysis is not dependent on lipoprotein lipase. Fat soluble vitamin supplements are necessary. The therapeutic goal is to maintain triglyceride levels below 1000 mg/dl to eliminate the risk of pancreatitis,.
Mortality is mainly due to pancreatitis. Ultimate prognosis appears to be good if strict dietary fat restriction is maintained and also because accelerated atherosclerosis has never been reported in this class of patients.
Primary hyperlipoproteinaemia has been reported in Indian literature, where the authors have suspected lipoprotein lipase deficiency as the cause. In the present case we have demonstrated this defect by estimating this enzyme and apoprotein C II levels.
We wish to thank Dr. P. M. Pai, Dean, Seth GS Medical College and KEM Hospital, Mumbai and Medical Superintendent, Masina Hospital, Mumbai for permission to publish this case report.
[Figure - 1]