Understanding Nakajo-Nishimura Syndrome

Nakajo-Nishimura Syndrome (NNS) is a very rare, inherited condition that causes episodes of fever and severe inflammation ^[1]. It was first identified in Japan, particularly in the Kansai region, but doctors now recognize it as a global condition with cases reported in other countries, including China and Algeria ^[2][3]. Because it is so rare, there is no exact count of how many people have it worldwide, but it is part of a larger group of related conditions that doctors are learning more about every year ^[4].

For patients and parents, hearing a diagnosis like NNS can be overwhelming. It is important to know that while this is a chronic and progressive condition, researchers have made significant breakthroughs in understanding the underlying biology, leading to the development of new, targeted treatments ^[5][6].

The PRAAS Umbrella

NNS is one of several conditions that fall under a larger “umbrella” known as PRAAS (Proteasome-Associated Autoinflammatory Syndromes) ^[1]. You may also hear names like CANDLE syndrome or JMP syndrome. While these were once thought of as separate diseases, we now know they are all part of the same biological spectrum ^[7].

• CANDLE syndrome: Often features early-onset fevers and skin lesions called panniculitis (inflammation of the fat layer under the skin) ^[8].
• JMP syndrome: Focuses on joint contractures, muscle loss (atrophy), and skin issues ^[1].
• NNS: Frequently includes fevers, a rash that looks like chilblains (pernio-like lesions), and a distinct pattern of fat loss in the face and upper body ^[1].

Why Inflammation Happens: Proteotoxic Stress

The root cause of classic NNS is a mutation in a gene called PSMB8 ^[1]. This gene provides instructions for building part of the immunoproteasome, which processes proteins within the cell ^[9].

In healthy cells, the proteasome breaks down proteins so the cell can function properly. In NNS, the PSMB8 mutation prevents this process from working efficiently ^[10]. When the process fails, it creates proteotoxic stress ^[9]. This stress sends a “danger signal” to the innate immune system, triggering an abnormal release of type I interferon—a powerful chemical that usually fights viruses but, in this case, causes constant, damaging inflammation throughout the body ^[11][9]. This state of constant immune activation is known as an interferonopathy ^[11].

Managing NNS and Emerging Treatments

While traditional treatments like oral corticosteroids often provide limited relief and carry severe side effects, newer “targeted” therapies are changing the outlook for PRAAS ^[4][5].

1. JAK Inhibitors: Drugs like baricitinib, tofacitinib, and ruxolitinib are sometimes used off-label to quiet the interferon signal ^[5]. In studies, some patients have seen improvements in their fevers and skin lesions when using these medications ^[5][6].
2. Monitoring and Safety: These treatments require careful supervision and are not without risk. They produce substantial immune suppression and carry class warnings. Doctors monitor for side effects, such as upper respiratory infections, lipid changes, or specific viral infections like herpes zoster or BK virus ^[5].
3. The Risk of Flares: It is vital to maintain consistent dosing. Research shows that missed doses or reductions in the dose of a JAK inhibitor can lead to a “flare” or a sudden return of symptoms ^[12].
4. Realistic Goals: An international task force emphasizes the need for multidisciplinary care that monitors the skin, joints, liver, and kidneys ^[13][14]. Treatments aim to reduce active inflammation but generally do not reverse established fat loss or joint contractures.

Managing NNS is a long-term journey. By understanding the biological “misfire” happening at the cellular level, you and your medical team can make informed decisions about the best ways to quiet the inflammation and protect your long-term health ^[13].