Molecular, genetic and epidemiologic studies on selective complete C1q deficiency in Turkey.

Selective complete C1q deficiencies (SCDC1q) of the complement component C1q are rare genetic disorders with high prevalence of lupus-erythematosus-like symptoms and recurrent infections. Among the 41 published cases from 23 families, 10 derive from 6 Turkish families. One particular mutation leading to a stop codon in the C1q A gene was first identified in members of a Gypsy family from the Slovac Republic. Later the same mutation has been found in all cases in four SCDC1q families from Turkey suggesting that one particular defective allele may be present in the populations of Southeastern Europe and Turkey. This study was undertaken to investigate the frequency of C-->T mutation in exon II of C1qA gene in Turkish population by using allele-specific polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism (PCR-RFLP). Among the 1544 patients from 15 pediatric departments and an additional 89 SLE patients of various ages no C1qA gene mutation was found. There were 43 heterozygous and 4 homozygous mutations in 161 family members or relatives investigated from the 4 families known with SCDC1q. Among the 223 inhabitants who were nonrelative to the 3 SCDC1q families living in the same village were screened for mutation and one heterozygous individual was observed. Although this mutant allele appears to be at a low prevalence in the population tested, individuals with recurrent infections or symptoms of lupus erythematosus-like syndrome should be tested for this mutation to rule out this type of C1q deficiency.