Hereditary angioedema with a de novo mutation of exon 8 in the C1 inhibitor gene showing recurrent edema of the hands around the peripheral joints - Importance for the differential diagnosis of joint swelling

We describe a patient with hereditary angioedema (HAE), showing recurrent e dema around the peripheral joints. Her symptoms began at the age of 18 with hand swelling distal to the wrist joints. Until she was referred to our ho spital 3 years after her initial symptoms, she was still undiagnosed, altho ugh she was suspected of having rheumatoid arthritis. Laboratory examinatio n showed reduced levels of CH50 and C4 with normal C3 levels. The C1 inhibi tor (Cl-INH) was decreased to 5 mg/ml, with remarkably reduced activity. Al though these findings were compatible with a diagnosis of HAE, there were n o episodes of skin edema in her family. To establish the diagnosis, we carr ied out DNA analysis of the Cl-INH gene, which revealed a newly identified de novo, mutation of G to A at nucleotide 16869 in exon 8. As described in this patient, localized edema around the peripheral joints may be the only manifestation of HAE. HAE should therefore be taken into consideration for the differential diagnosis of joint swelling.