C1q deficiency

C1q deficiency is a rare disorder associated with recurrent skin lesions, chronic infections, systemic lupus erythematosus (SLE) or SLE-like diseases. It has also been associated with a kidney disease known as mesangial proliferative glomerulonephritis.

C1q is a protein and together with other proteins, C1r and C1s, it forms the C1 complex. This complex is important for the activation of the complement system (a group of proteins that work with the immune system). It also disposes cells that are dead. C1q deficiency presents in 2 different forms, absent C1q protein or abnormal C1q protein.

Lack of production of functional c1q proteins, due to a genetic defect. Virtually 100% of patients with a c1q deficiency will develop a severe systemic lupus erythematosus at an early age. Patients also present with frequent sinopulmonary infections often with streptococcus pneumoniae.

Cause

It can be caused by mutations in the C1QA, C1QB or C1QC genes.

Inheritance

Autosomal recessive inheritance, a 25% chance

It is inherited in an autosomal recessive pattern.

Signs and symptoms

Symptoms include infections (ear infections (otitis media), meningitis, urinary tract infections, oral infections); skin lesions (small blisters (vesicles), dark patches, and atrophic areas) that get worse upon light exposure; cataracts; loss of eyelashes, eyebrows, and scalp hair; blood in urine; and glomerulonephritis. About 93% of cases are associated with systemic lupus erythematosus.

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 5%-29% of people have these symptoms

• Membranoproliferative glomerulonephritis
• Systemic lupus erythematosus

Treatment

Treatment depends on the symptoms. Recently, it was shown that C1q production can be restored by allogeneic hematopoietic stem cell transplantation, a procedure in which a person receives blood-forming stem cells (cells from which all blood cells develop) from a genetically similar, but not identical donor.

NIH genetic and rare disease info

• NIH info on C1q deficiency

C1q deficiency is a rare disease.