Pyogenic Sterile Arthritis Pyoderma Gangrenosum and Acne Syndrome

PAPA syndrome, PAPAS, Familial recurrent arthritis, FRA, Pyogenic arthritis-pyoderma gangrenosum-acne syndrome

D89.8; M04.8
4A60.Y
C536253
10072222

PAPA syndrome is a rare genetic condition that causes recurring joint inflammation, severe skin ulcers, and acne. It typically begins with joint problems in early childhood and develops skin symptoms during the teenage years.

Table of contents

• What is PAPA Syndrome?
• How Common is the Condition?
• Causes and Inheritance
• Main Symptoms
• Diagnosis
• Treatment Options
• Long-term Outlook

What is PAPA Syndrome?

PAPA syndrome is a rare genetic disorder that primarily affects the joints and skin. The name PAPA is an acronym that stands for Pyogenic Arthritis (joint inflammation), Pyoderma gangrenosum (a type of skin ulcer), and Acne. It is classified as an autoinflammatory disorder, which means the body’s immune system mistakenly causes inflammation in its own tissues without an infection being present.^[1][2]

The condition is characterized by three main features that rarely appear together at the same time in the same person. The arthritis usually appears first during childhood, while the skin problems typically become more prominent during adolescence and continue into adulthood.^[2][3]

How Common is the Condition?

PAPA syndrome is extremely rare. Only 34 patients with this condition have been reported worldwide, from five families in the United States, Italy, the Netherlands, and New Zealand.^[3] However, the actual frequency may be higher because the disease can be difficult to recognize and may be underestimated.^[2]

The syndrome affects males and females equally. The disease usually begins to show symptoms during childhood, although the specific age of onset and severity can vary significantly between individuals.^[2]

Causes and Inheritance

Genetic Basis

PAPA syndrome is caused by changes (mutations) in a gene called PSTPIP1, which was previously known as CD2BP1. This gene provides instructions for making a protein that plays an important role in controlling the body’s inflammatory response. When mutations occur in this gene, the protein’s function changes, leading to excessive inflammation in the joints and skin.^[2][3]

Research has shown that only two specific mutations account for all the known cases of PAPA syndrome. The PSTPIP1 protein has been found to interact with another protein called pyrin, which is involved in a related condition called Familial Mediterranean Fever. Mutated PSTPIP1 proteins show increased binding to pyrin, which may contribute to the disease process.^[3]

How It Is Inherited

PAPA syndrome is inherited in an autosomal dominant pattern. This means that only one copy of the changed gene is needed to cause the condition. Because it is autosomal, the condition is not linked to gender and can affect both males and females equally.^[2][4]

When a parent has PAPA syndrome, there is a 50% chance with each pregnancy that their child will inherit the condition. Usually, one parent shows at least some symptoms of the disease, and affected individuals can be observed across multiple generations in a single family.^[2]

A child has this disease because they inherited the mutation from one of their parents who carries the changed PSTPIP1 gene. The parent with the mutation may or may not show all symptoms of the disease. The disease itself cannot be prevented, but the symptoms can be managed with treatment.^[2]

Main Symptoms

The three main symptoms of PAPA syndrome are arthritis, pyoderma gangrenosum, and cystic acne. It is important to note that rarely are all three features present in the same patient at the same time.^[2][4]

Arthritis

Arthritis is usually the first symptom to appear, typically occurring early in childhood between 1 and 10 years of age. The arthritis in PAPA syndrome has several distinctive characteristics. It usually affects one joint at a time (pauciarticular), commonly involving large joints such as the elbow, knee, or ankle. The affected joint becomes swollen, painful, and red.^[2][4]

The arthritis episodes are sterile, meaning there is no bacterial infection present, even though the clinical appearance strongly resembles septic arthritis (arthritis caused by bacteria in the joint). When fluid is examined from an affected joint, it contains many white blood cells called neutrophils, but cultures show no bacteria. Episodes often occur after minor injuries to the joint, though they can also happen spontaneously.^[2][3]

Without proper treatment, repeated arthritis episodes can cause damage to the cartilage and bone around the joint. In severe cases, multiple joint replacements may be required. However, arthritis symptoms often tend to improve as children grow older.^[2][4]

Pyoderma Gangrenosum

Pyoderma gangrenosum is a serious skin condition that typically appears later than the arthritis. It is characterized by large, painful ulcers with distinctive raised and undermined edges. These ulcers often involve the legs and heal very poorly.^[2][4]

An important feature of pyoderma gangrenosum in PAPA syndrome is pathergy, which refers to the tendency of ulcers to develop at sites of minor skin injury. There are reports of lesions appearing at surgical sites, where joint replacements were performed, and at sites where needles were inserted, such as for central venous lines or intravenous drips.^[3][4]

Not all individuals with PAPA syndrome develop pyoderma gangrenosum, as this feature shows variable expression between affected people.^[4]

Acne

Cystic acne usually appears during adolescence and may persist into adulthood. It affects most individuals with PAPA syndrome but varies in severity from person to person. The acne is typically of a severe type with deep, pus-filled cysts that, if left untreated, can result in permanent scarring. The acne commonly involves the face and trunk.^[2][4]

Variable Presentation

The disease is not the same in every person. An individual carrying a mutation in the PSTPIP1 gene may not show all symptoms of the disease or may have only very mild symptoms. This characteristic is called variable penetrance. Additionally, the symptoms may change over time, usually improving as a child grows older. Symptoms are often triggered by minor injuries to the skin or joints.^[2]

Diagnosis

Diagnosing PAPA syndrome can be challenging. There are no single definitive tests, and the diagnosis is often delayed because the condition can resemble other diseases.^[2][4]

When to Consider PAPA Syndrome

Healthcare professionals may consider PAPA syndrome in a child who has repeated episodes of painful inflammatory arthritis that looks like septic arthritis but does not respond to antibiotic treatment. The arthritis and skin problems may not appear at the same time and may not be present in all affected individuals.^[2]

A detailed evaluation of family history is important. Because the disease is autosomal dominant, other family members are likely to show at least some symptoms of the condition.^[2]

Diagnostic Approach

The clinical features combined with a family history of similar symptoms may be sufficient to make a diagnosis. However, genetic testing for mutations in the PSTPIP1 gene may be available at some specialized centers and can confirm the diagnosis.^[4]

When joint fluid is examined during an arthritis episode, it appears purulent (pus-like) with many neutrophils, but cultures are always negative for bacteria. Skin biopsies show prominent inflammation with a predominance of neutrophil white blood cells. In pyoderma gangrenosum lesions, biopsies reveal superficial ulceration along with neutrophilic inflammation.^[3][4]

Conditions That May Resemble PAPA Syndrome

Because PAPA syndrome is rare and its symptoms can look like other conditions, doctors must consider other possible diagnoses. These include juvenile idiopathic arthritis and other periodic fever syndromes. PAPA syndrome is ultimately a diagnosis of exclusion, meaning other possible causes must be ruled out.^[3]

Treatment Options

Treating PAPA syndrome can be challenging. Because the condition is so rare, conducting large clinical trials is difficult, and there is no single “gold standard” treatment. Patients often require aggressive therapy with medications that suppress the immune system.^[3]

Treatment for Acne

The severe cystic acne associated with PAPA syndrome may require oral tetracycline antibiotics or a medication called isotretinoin, which is specifically designed to treat severe acne.^[4]

Treatment for Arthritis and Skin Ulcers

Arthritis and skin lesions sometimes respond to glucocorticoids (steroid medications that reduce inflammation). However, more targeted treatments have shown promising results in recent years.^[3]

Several newer treatments called biological response modifiers have been used successfully. These medications target specific inflammatory proteins in the body. Two main categories have shown good responses in resistant arthritis and pyoderma gangrenosum:^[4]

Tumor necrosis factor (TNF) inhibitors include medications such as infliximab, etanercept, and adalimumab. In one report, the disease went into rapid and sustained remission after treatment with etanercept, a TNF inhibitor.^[3][4]

Interleukin-1 (IL-1) blockers, particularly a medication called anakinra (a recombinant human IL-1 receptor antagonist), have been described as effective therapy to treat disease flares in PAPA syndrome.^[3][7]

These medications have shown success in treating other inflammatory conditions such as rheumatoid arthritis and psoriasis, and they appear to work well for PAPA syndrome too.^[4]

Long-term Outlook

PAPA syndrome is described as a self-limiting disease, meaning that symptoms may improve over time. However, without proper treatment, it can lead to severe joint destruction. The arthritis symptoms often tend to improve as affected individuals grow older, while skin problems may become more prominent during and after adolescence.^[2][3]

With improved treatment options, particularly the newer biological therapies, there is hope that joint damage can be limited in newly diagnosed cases. Early diagnosis and appropriate treatment are important to minimize complications and improve quality of life.^[4]

The disease cannot be prevented because it is inherited, but symptoms can be treated effectively with current therapies. Because PAPA syndrome is not infectious, it cannot be spread from person to person through contact.^[2]