- Glomerulonephritis (HP:0000099): Inflammation of the renal glomeruli. Evidence: TAS. (OMIM:614380)
- Cutaneous photosensitivity (HP:0000992): An increased sensitivity of the skin to light. Photosensitivity may result in a rash upon exposure to the sun (which is known as photodermatosis). Photosensitivity can be diagnosed by phototests in which light is shone on small areas of skin. Evidence: TAS. (OMIM:614380)
- Reduced circulating CH50 activity (HP:0025434): A diminished activity of the classical complement pathway as measured by the assay for 50% haemolytic complement (CH50) activity of serum. Evidence: TAS. (OMIM:614380)
- Purpura (HP:0000979): Purpura (from Latin: purpura, meaning purple) is the appearance of red or purple discolorations on the skin that do not blanch on applying pressure. They are caused by bleeding underneath the skin. This term refers to an abnormally increased susceptibility to developing purpura. Purpura are larger than petechiae. Evidence: TAS. (OMIM:614380)
- Autosomal recessive inheritance (HP:0000007): A mode of inheritance that is observed for traits related to a gene encoded on one of the autosomes (i.e., the human chromosomes 1-22) in which a trait manifests in individuals with two pathogenic alleles, either homozygotes (two copies of the same mutant allele) or compound heterozygotes (whereby each copy of a gene has a distinct mutant allele). Evidence: TAS. (OMIM:614380)
- Systemic lupus erythematosus (HP:0002725): A chronic, relapsing, inflammatory, and often febrile multisystemic disorder of connective tissue, characterized principally by involvement of the skin, joints, kidneys, and serosal membranes. Evidence: TAS. (OMIM:614380)
- Decreased circulating complement C4 concentration (HP:0045042): Concentration of the complement component C4 in the blood circulation below the lower limit of normal. Evidence: TAS. (OMIM:614380)
- Vasculitis (HP:0002633): Inflammation of blood vessel. Evidence: TAS. (OMIM:614380)
These phenotypes are associated with the disease complement component 4a deficiency (OMIM:614380).