Definition
Diseases associated with mutations in PSTPiP1 (Proline-Serine-Threonine Phosphatase-interacting Protein 1) are rare diseases. The gene codes for the PSTPIP1 protein, which is involved in the cytoskeleton of cells.
In the event of a mutation, patients develop an inflammatory disease known as PAID (PSTPiP1 Associated Inflammatory Disease).
It is a rare cosmopolitan disease affecting at least 200 patients worldwide.
Symptoms usually begin in childhood.
Given its rarity, some patients are diagnosed in adulthood.
Genetic
PAID is transmitted in the autosomal dominant mode: therefore usually an affected subject has one of his affected parents.
Clinical
There are several clinical forms of PAID:
-PAPA syndrome (Pyogenic Arthritis, Pyoderma gangrenosum and Acne syndrome) is the most common and the 1st described; it is characterised by recurrent episodes of fever, severe acne, pyoderma gangrenosum (PG) and sterile arthritis in the peripheral joints (knees, ankles and elbows).
Verneuil's disease may be associated, resulting in a syndrome known as PAPASH (Pyoderma gangrenosum, Acne and Suppurative Hidradenitis).
-PAMI syndrome (PSTPIP1-Associated Myeloid-related proteinemia Inflammatory syndrome) is a severe form, which begins early in life at around 2 years of age, and combines a chronic biological inflammatory syndrome with delayed growth and cytopenias. Arthritis and skin involvement are frequent but less systematic than in PAPA syndrome.
Diagnostic
Diagnosis is based on genetic analysis, which involves taking blood samples to search for a pathogenic mutation in the PSTPiP1 gene.
PAID is transmitted in an autosomal dominant fashion, which means that an affected person usually has one affected parent.
The referring physician may suggest that family members be consulted in order to identify other people with the disease.
There is an increase in interleukin 18 in the blood of affected patients, which can be measured by routine blood tests in certain laboratories.
Evolution
The disease usually progresses in flare-ups. If left untreated, destructive joint damage may occur. Renal amyloidosis (RA) may also complicate the disease.
Treatment and follow-up must be coordinated by the expert doctor in collaboration with the general practitioner, paediatrician and certain organ specialists depending on the extent of the disease (rheumatologist, nephrologist, etc.).
Treatment
The treatment is not codified and difficult. Anti-interleukin 1 biotherapies seem effective in severe forms, particularly with arthritis and pyoderma gangrenosum. Treatment of PAMI may require bone marrow allograft.
Follow-up
In the case of disease associated with a confirmed PSTPiP1 mutation, and given the rarity of the disease, follow-up by a doctor with expertise in the disease is advisable.
It seems important to consult your specialist twice a year and to monitor inflammation in the blood by measuring CRP every 6 months. At least once a year, a haemogram should be carried out, and creatinine levels, interleukin 18 and the protein/creatinine ratio checked.