[Laboratory diagnosis of rare diseases]

Inborn errors of metabolism (IEM) are a group of diseases whose diagnosis is usually performed by quantification of several metabolites in biological fluids. The aim of this review is to report the role of the laboratory in IEM diagnosis, highlighting the methods available at present and their advantages and limitations. In conclusion, the huge number of recognized IEMs strongly advises the implementation of new high- output technologies in the laboratories devoted to IEM diagnosis. Although these technologies offer a high diagnostic ability, routine analyses are still very important, as well as consideration of several variables involved in biological sample collection and disease expression that may lead to misdiagnosis of IEMs.

[Proposed protocol for the study of cerebrovascular disease in childhood]

AIM

The etiology of cerebrovascular disease in the paediatric population, remains unknown in up to 40% of the cases ("idiopathic"), but recent advances could improve this percentage. We devised a comprehensive study protocol for such investigation aimed at the identification of potentially modifiable risk factors for paediatric stroke.

PATIENTS AND METHODS

From the 141 patients initially registered in our data base for stroke population (from January 1984 until December 1995), we invited all the patients with idiopathic cerebrovascular disease to complete the study protocol. New cases appeared from January 1996 until July 1999 were also included.

RESULTS

A total of 68 cases were identified. We found an etiology in 38% and in 76% of the cases we found at least one risk factor for stroke. Mild hyperhomocysteinemia was the most frequent risk factor identified (36% of patients versus 5% of controls), one of them an infant with fatal haemorrhagic infarct with classic homocystinuria. 31% of the patients had thrombotic risk factors (protein S, protein C, antithrombine III deficiency, factor V Leiden, etc). 17.6% had unspecific febrile illness at the time of the cerebral infarction and 11.6% had minor head injuries before the stroke.

CONCLUSIONS

The use of the protocol improves the identification of potentially modifiable risk factors for stroke in childhood and may serve as a practical guideline for clinicians. The stroke protocol is as important as management strategies for acute stroke or for recurrence prevention, currently under consideration in the adult population.

[The relationship of lipoprotein(a) to metabolic control in infantile-juvenile diabetes mellitus]

Lipoprotein (a) has become of great interest as a biochemical marker for predicting the risk of developing cardiovascular alterations, with increased levels suggesting patients at a higher risk. We have realized a study of the plasma concentrations of lipoprotein (a) and other constituents of lipoprotein metabolism in children diagnosed with diabetes mellitus type I in relationship to the levels of metabolic control, the time of evolution of the disease and the presence or not of microalbuminuria (albumin in the urine greater than 30 micrograms/min). The study population was comprised of 211 children, between the ages of 3 and 18 years of age, divided into three groups according to the time of evolution of the disease: beginners (n = 15), time of evolution less than or equal to 5 years (n = 99) and more than 5 years (n = 92). All determinations were performed on specimens collected after 10 hours of fasting and before the morning dose of insulin. The following determinations were made: total cholesterol, triglycerides, cHDL, cLDL, cVLDL, Apo AI, Apo B, lipoprotein (a), albumin excretion rate (AER), glucose, fructose, glycosylated hemoglobin and creatinine clearance. We found significant differences between the groups in function of the existence of microalbuminuria and if the time of evolution of the disease exceeded 5 years. In conclusion, it appears that metabolic control does not influence the concentrations of lipoprotein (a), with an increased risk of cardiovascular alterations in those patients with a long disease evolution an those that have microalbuminuria.