Sweat test is the standard for cystic fibrosis (CF) diagnosis. Conductivity is an alternative method not yet approved, in spite of its good correlation with chloride concentration. The aim was to assess the capacity of sweat conductivity to discriminate between CF and non-CF subjects. Automated measurements of conductivity and chloride concentration were carried out on the same sweat samples from subjects with clinical suspicion of CF. Sweat samples from 3,834 subjects, median age 1.8 years (range 1 month-54 years) were analysed, and those with chloride titration >60 mmol/l were considered as CF patients (n=294). Conductivity median values in CF and non-CF subjects were 111 mmol/l (82-148) and 36 mmol/l (12-89), respectively. The Spearman correlation between chloride titration and conductivity was r=0.60 (P<0.001). The receiver operating characteristics (ROC) curve showed very high agreement between two methods. The best conductivity cut-off value to diagnose CF was > or =90 mmol/l (sensitivity 99.7%, specificity 100%, positive and negative predictive values of 100% and 99.97%, respectively, and kappa=0.998). Likewise, the best conductivity cut-off value to exclude CF was <75 mmol/l. The sweat conductivity method showed good correlation with chloride titration, and accurately discriminated between subjects with and without CF. In accordance with this, CF diagnosis might be confirmed for conductivity values > or =90 mmol/l and excluded for <75 mmol/l. Values between 75 and 89 mmol/l should correspond to an equivocal range. However, more studies are needed to confirm the role of conductivity in definitive CF diagnosis.

We have analyzed 97 CF unrelated Mexican families for mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Our initial screening for 12 selected CFTR mutations led to mutation detection in 56.66% of the tested chromosomes. In patients with at least one unknown mutation after preliminary screening, an extensive analysis of the CFTR gene by single stranded conformation polymorphism (SSCP) or by multiplex heteroduplex (mHET) analysis was performed. A total of 34 different mutations representing 74.58% of the CF chromosomes were identified, including five novel CFTR mutations: W1098C, P750L, 846delT, 4160insGGGG and 297-1G-->A. The level of detection of the CF mutations in Mexico is still lower than that observed in other populations with a relatively low frequency of the deltaF508 mutation, mainly from southern Europe. The CFTR gene analysis described here clearly demonstrated the high heterogeneity of our CF population, which could be explained by the complex ethnic composition of the Mexican population, in particular by the strong impact of the genetic pool from southern European countries.

Patients with interleukin 12 (IL-12)p40 or IL-12 receptor β1 (IL12Rβ1) deficiencies are prone to develop infections caused by mycobacteria and salmonella; other infections have only been rarely observed. In this report we describe 2 unrelated patients with complete autosomal recessive IL12Rβ1 deficiency who suffered from sepsis attributable to Klebsiella pneumoniae. A Mexican boy suffered from disseminated bacilli Calmette-Guérin disease and infections caused by K pneumoniae and Candida albicans and had a fatal outcome. A Turkish girl living in France suffered from disseminated Nocardia nova infection and K pneumoniae sepsis. Therefore, Klebsiella infections should be considered in patients with IL12Rβ1 deficiency. Conversely, IL12Rβ1 deficiency should be considered in patients with unexplained klebsiellosis. CASE REPORTS Patient 1Patient 1 was a mestizo (European/Amerindian) boy born in Veracruz, Mexico, in 2002 to nonrelated parents. His older sibling received bacille Calmette-Guérin (BCG) vaccination at birth without any adverse reaction and remains healthy; in contrast, patient 1 was vaccinated against BCG during his first month of life and developed axillary BCGitis at the age of 8 months. Despite antimycobacterial treatment given at standard doses (including isoniazid [at 9 months], isoniazid plus rifampin [at 6 months], and isoniazid, rifampin, and ethambutol [at 3 months]), lymphadenitis extended to his cervical nodes. During this time, a bone marrow culture was positive for nontyphoidal Salmonella, and he was treated with chloramphenicol. Antimycobacterial treatment for a total of 26 months resulted in intermittent improvements but no cure.At the age of 3½ years, after 6 months without any treatment, he was admitted to the hospital with hepatosplenomegaly and multiple lymphadenitis with failure to thrive; HIV serology results were negative, and results of polymerase chain reaction and serology for Epstein-Barr virus (immunoglobulin G for viral capsid antibody) were positive. A biopsy of the cervical lymph node revealed a loss of lymph node architecture with noncaseating lymphoepithelioid granulomas and numerous Langerhans cells and tested positive for acidfast bacilli. Daily treatment with isoniazid, rifampin, ethambutol, and ciprofloxacin was initiated. Despite this treatment, the patient was readmitted to the hospital 8 months later at the age of 4½ years with fever, weight loss, progressive dyspnea, thrush, generalized lymphadenitis, and the presence of abscesses at the posterior upper thorax wall, on the scapula, and in the lumbar region. The dorsolumbar abscess required surgical debridement, and the culture obtained from the excised material was positive for Mycobacterium bovis, Pedraza et al.

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