Mendelian Susceptibility to Mycobacterial Disease (MSMD): Clinical, Immunological, and Genetic Features of 22 Patients from 15 Moroccan Kindreds.

PURPOSE: The first molecular evidence of a monogenic predisposition to mycobacteria came from the study of Mendelian susceptibility to mycobacterial disease (MSMD). We aimed to study this Mendelian susceptibility to mycobacterial diseases in Moroccan kindreds through clinical, immunological, and genetic analysis. METHODS: Patients presented with clinical features of MSMD were recruited into this study. We used whole blood samples from patients and age-matched healthy controls. To measure IL-12 and IFN-γ production, samples were activated by BCG plus recombinant human IFN-γ or recombinant human IL-12. Immunological assessments and genetic analysis were also done for patients and their relatives. RESULTS: Our study involved 22 cases from 15 unrelated Moroccan kindreds. The average age at diagnosis is 4 years. Fourteen patients (64%) were born to consanguineous parents. All patients were vaccinated with the BCG vaccine, and twelve of them (55%) developed locoregional or disseminated BCG infections. The other symptomatic patients had severe tuberculosis and/or recurrent salmonellosis. Genetic mutations were identified on the following genes: IL12RB1 in 8 patients, STAT1 in 7 patients; SPPL2A, IFNGR1, and TYK2 in two patients each; and TBX21 in one patient, with different modes of inheritance. All identified mutations/variants altered production or response to IFN-γ or both. CONCLUSION: Severe forms of tuberculosis and complications of BCG vaccination may imply a genetic predisposition present in the Moroccan population. In the presence of these infections, systematic genetic studies became necessary. BCG vaccination is contraindicated in MSMD patients and should be delayed in newborn siblings until the exclusion of a genetic predisposition to mycobacteria.

An autosomal dominant major gene confers predisposition to pulmonary tuberculosis in adults.

The molecular basis of genetic predisposition to pulmonary tuberculosis in adults remains largely elusive. Few candidate genes have consistently been implicated in tuberculosis susceptibility, and no conclusive linkage was found in two previous genome-wide screens. We report here a genome-wide linkage study in a total sample of 96 Moroccan multiplex families, including 227 siblings with microbiologically and radiologically proven pulmonary tuberculosis. A genome-wide scan conducted in half the sample (48 families) identified five regions providing suggestive evidence (logarithm of the odds [LOD] score >1.17; P < 0.01) for linkage. These regions were then fine-mapped in the total sample of 96 families. A single region of chromosome 8q12-q13 was significantly linked to tuberculosis (LOD score = 3.49; P = 3 x 10(-5)), indicating the presence of a major tuberculosis susceptibility gene. Linkage was stronger (LOD score = 3.94; P = 10(-5)) in the subsample of 39 families in which one parent was also affected by tuberculosis, whereas it was much lower (LOD score = 0.79) in the 57 remaining families without affected parents, supporting a dominant mode of inheritance of the major susceptibility locus. These results provide direct molecular evidence that human pulmonary tuberculosis has a strong genetic basis, and indicate that the genetic component involves at least one major locus with a dominant susceptibility allele.

B/T mixed phenotype acute leukemia with high hyperdiploidy and lineage switch to B-cell acute leukemia.

Acute leukemias are often of myeloid or lymphoid origin. However, some acute leukemias revealed an undefined differentiation into a single lineage. Mixed phenotype acute leukemia (MPAL) is an uncommon diagnosis were blasts can share B/T/myeloid phenotype. Here, we report a rare case of a 17-year-old Moroccan female diagnosed with B/T mixed phenotype acute leukemia and a high hyperdiploid karyotype who relapsed after one year of complete remission with a lineage switch to B-cell acute lymphoblastic leukemia. This case report corroborates the disclosed findings about the high occurence of abnormal karyotypes and poor prognosis of MPAL.