A 22-year-old male patient complained about a history of painless recurrent swelling of both knees for 17 years. He was susceptible to upper respiratory tract infections since 3 years old. He was diagnosed as having aseptic synovitis at 5 years old and treated with prednisolone for 3 months. However, the joint swelling progressively aggravated. Six years ago, he received arthroscopic synovectomy with complete resolution of the clinical symptoms. The pathology of synovial biopsy showed chronic hyperplasia synovitis with fatty infiltration. Four years ago, the symptom of joint swelling relapsed. The painless swelling of both knees was persistent, without deformity of joints. He then came to our hospital for further diagnosis and treatment.
The physical examination revealed that both knees were swelling without tenderness. Fluctuation and patellar tap test was positive. The magnetic resonance imaging (MRI) of the knees showed massive effusion associated with multiple frond like synovial thickening of high signal intensity in sagittal T1 weighted image especially in the suprapatellar region (Figure 1). Fat suppressed proton density images (Figure 1) revealed complete suppression of signal intensity of villous projections in suprapatellar region. Synovial biopsy guided by the ultrasound was performed and the histopathologic examination revealed a fibroadipose synovial membrane with small vascular proliferation and a small amount of lymphocytes and mononuclear cells infiltration (Figure 2). The diagnosis of LA was made according to the features of MRI and synovial pathology.
The laboratory tests including autoantibodies, HIV, HBsAg, HCV-Ab, and syphilis antibody were normal. Cytologic and biochemical examinations of synovial fluid were normal. Synovial fluid culture showed no growth of pathogen. The lymphocyte culture and interferon determination and synovial fluid analysis for acid-fast bacilli were negative which excluded the tuberculosis infection. There were no history or clinical and pathological findings which were suggestive of infectious arthritis. However, the ESR was 90 mm/h (0-15 mm/h) and CRP was 1.3 mg/dL (0-0.8 mg/dL). The blood routine showed neutropenia and immunoglobulin test revealed deficiency of IgG (0.34 g/L, normal range 6.94-16.18 g/L) and IgA (0.07 g/L, normal range 0.7-3.8 g/L) with high level of IgM (23 g/L, normal range 0.6-2.3 g/L). Bone marrow examination was normal. He was suspected to have hyperimmunoglobulin M syndrome (HIGM). Gene test was performed to confirm the type of HIGM. It revealed a deletion of cytidylic acid residue in exon 5 region at position 520 (c.520delC) which led to a shift in the encoding of the reading frame from position 174 (p.Gln174fs). Premature termination occurred in 190 amino acids (numbering according to Hollenbaugh et al.; Figure 3(a)). The patient's mother carried the same mutation (Figure 3(b)). Therefore, the diagnosis of X-linked HIMG was made. Informed consent for sequence analysis was obtained from the patient and his mother.
Interestingly, splenic hemangioma (5.8*5.0 cm) was found by the contrast abdominal CT scan. He had no symptoms. There was no surgical indication of the vascular tumor. We suggested he follow up closely with regular ultrasound examination once a year.
The patients received synovectomy operation and were given regular IVIG therapy with 15 g * 3 days (total dose of 600 mg/kg, 75 kg) every month. No relapse of LA or infection occurred during one-year follow-up period.