Cause
The cause is unknown but allergic and auto-inflammatory mechanisms have been proposed.In a 1957 review of IH, Mattingly did not find evidence that the condition is inherited unlike Reimann who, in 1974, describes the condition as “heritable, non-inflammatory, and afebrile”.More recently, specific association with the Mediterranean fever gene, MEFV, has been proposed. So, with some individuals carrying gene mutations (MEFV and also TRAPS-related genes), the native immune system seems to plays a role in the development of IH, i.e. there is an auto-immune component to the condition. Pathophysiology
Involvement of mast cells has been reported  reflecting a possible immunoallergic aspect to IH. Mattingly suggests that IH may be an unusual variant of rheumatoid arthritis, and some patients may go on to develop RA. Joint damage however does not generally occur and only the synovial membrane is affected by a ‘non-inflammatory oedema’.With regard to the periodic nature of effusions, Reimann theorises that:
“…either an inherent rhythm or a feedback mechanism (Morley, 1970) excites bioclocks in the hypothalamus or in the synovial membrane (Richter, 1960). These Zeitgebers provoke sudden accumulation of plasma in the lining and spaces of joints, tendon and ligament sheaths.”

Diagnosis
There is no specific test for this condition. Diagnosis is based on signs and symptoms, and exclusion of other conditions. Differential diagnoses
Rheumatoid arthritis. Confusion with rheumatoid arthritis may be common even though IH is a non-inflammatory condition without the many signs and symptoms associated with RA. So far, an association with HLA-B27 gene in IH has not been reported.
More aggressive treatments such as synovectomy, achieved using intra-articular agents (chemical or radioactive) can provide good results, with efficacy reported for at least 1 year.Reducing acute joint swelling:
Arthrocentesis (or drainage of joint) may be useful to relieve joint swelling and improve range of motion. Local steroid injections can also reduce fluid accumulation short-term, but do not prevent onset of episodes. These treatments provide temporary relief only. Bed rest, ice packs splints and exercise are ineffective.A single case report of a patient with treatment-refractory IH describes the use of anakinra, an interleukin 1 receptor antagonist. At the first sign of any attack, a single 100 mg dose was given. With this dosing at onset of attacks, each episode of effusion was successfully terminated.Reducing frequency and severity of IH episodes:
Case reports indicate some success using long-term, low-dose colchicine (e.g. 0.5 mg to 1 mg daily). A recent single case report has shown hydroxychloroquine (300 mg daily) to be effective too.Small-sized clinical trials have shown positive results with (1) chemical and (2) radioactive synovectomy. (1) Setti et al. treated 53 patients with rifampicin RV (600 mg intra-articular injections weekly for approximately 6 weeks) with good results at 1 year follow-up. (2) Top and Cross used single doses of intra-articular radioactive gold in 18 patients with persistent effusions of mixed causes including 3 with IH. All 3 patients with IH responded well to treatment at one-year follow-up. Prognosis
Once established, periods of remissions and relapse can persist indefinitely. While IH may remit spontaneously for most people the condition is long-lasting.