Jh. Slingsby et al., HOMOZYGOUS HEREDITARY CLQ DEFICIENCY AND SYSTEMIC LUPUS-ERYTHEMATOSUS- A NEW FAMILY AND THE MOLECULAR-BASIS OF CLQ DEFICIENCY IN 3 FAMILIES, Arthritis and rheumatism, 39(4), 1996, pp. 663-670
Objective. To describe a new kindred with Clq deficiency and to identi
fy the molecular lesions responsible for complete functional Clq defic
iency in this and 2 other previously described kindreds. Methods. The
A-, B-, and C-chain genes of C1q were amplified by polymerase chain re
action, cloned, and sequenced. The DNA sequence was checked for mutati
ons. Results. Patient 1 had a homozygous G-to-A change at codon 6 of t
he C chain, causing an amino acid change from Gly to Arg. Patient 2 ha
d a homozygous deletion of a C nucleotide at codon 43 of the C-chain,
causing a frame shift, leading to a premature stop codon at codon 108,
Patient 3 had a homozygous C-to-T mutation at amino acid position 41
of the C chain, resulting in a premature stop codon. Conclusion. In th
e homozygous state, the mutations are sufficient to cause complete def
iciency of Clq. The mutation in patient 1 has been previously reported
in a patient of different ethnic origin, A survey of a series of 158
DNA samples from patients with systemic lupus erythematosus showed no
other examples of this mutant allele.