Symptomatic patients with P369S–R408Q mutations: familial Mediterranean fever or mixed auto-inflammatory syndrome?

Abstract

A 51-year-old South African female of Ashkenazi Jewish descent was admitted with acute pleuritic chest pain, shortness of breath, fatigue and fever. She experienced vague abdominal and calf pains for 30 years. Her monozygotic twin was investigated independently for recurrent abdominal pain. Despite initially responding to antibiotics, treating suspected pneumonia, she developed recurrent fevers and pleuritic chest pain. After thorough investigation without significant findings, she re-attended days after discharge with similar symptoms. Familial Mediterranean fever (FMF) was suggested as she met diagnostic criteria and responded to colchicine, though FMF normally presents before 20 years old. Genetic testing showed no pathogenic mutations but heterozygous P369S and R408Q mutations. The significance of these mutations remains unclear, as they are found in asymptomatic patients, suggesting incomplete penetrance. She remains well, with full symptom resolution, but mixed auto-inflammatory syndrome may be a more appropriate diagnosis in symptomatic patients with both P369S and R408Q mutations.

Background

This case proved to be a diagnostic conundrum for various medical teams (rheumatology, respiratory, cardiology and haematology). The patient had a lengthy admission, which was compounded by considerable anxiety, frustration and low mood given the length of stay and diagnostic uncertainty. After reasonable time and treatment given in order to treat infection, her pleuritic chest pain and fevers recurred. Many further investigations were carried out, yielding no significant results. Following re-admission with similar symptoms, familial Mediterranean fever (FMF) was suggested as a possible diagnosis.

FMF is a disease not commonly seen in the UK, though it should be considered in ‘at risk’ populations. While her symptoms were typical of FMF, her age at presentation and lack of pathogenic mutations go against this diagnosis. She was found to have heterozygous P369S and R408Q mutations. These mutations are relatively common in the Ashkenazi Jewish population, though often in asymptomatic patients, so incomplete penetrance has been suggested. This case highlights the difficulty in diagnosing auto-inflammatory conditions and that genetic testing does not necessarily provide a clear-cut outcome.

Case presentation

A 51-year-old South African female of Ashkenazi Jewish descent presented with a 4-week history of fever, pleuritic left-sided chest pain and shortness of breath. During this time, she had received a course of amoxicillin from her general practitioner, which had not helped her symptoms. She had been having intermittent chest pain and fatigue for the previous 18 months. She described intermittent abdominal pains, up to several times per week for some 30 years, and calf pains. She had no lymphadenopathy, no skin/joint abnormalities, no cough and no weight loss.

She had a prior medical history of peptic ulcer disease, depression and was a social smoker. She works in a physically demanding job in retail and lives with her husband and children, who were physically well. She has a monozygotic twin sister, living in Israel, who had a similar history of recurrent abdominal pain. She has no known drug allergies and was taking no medication on admission. Her recent travel history was not significant, though she had visited various African countries some 17 years ago.

On examination, she had reduced air entry in the upper zones and crackles in the left lung base. Initial observations showed respiratory rate 22, oxygen saturations 90% on room air, temperature 39.9°, heart rate 118, blood pressure 106/88. Chest X-ray showed left-sided consolidation. Blood tests revealed elevated C-reactive protein (CRP) 405 mg/dL, raised white cell count, mildly deranged liver function tests and D-Dimer >1000 µg/mL. Her renal profile was normal and urine dipstick was negative. She was diagnosed with left lower lobe community acquired pneumonia, which was confirmed with CT of the thorax. A small pericardial effusion was also noted. Ultrasound scan (USS) thorax showed a small pleural effusion, which was aspirated and found to be an exudative, sterile effusion (pH 7.4, protein 55 g/L, LDH 184 IU/L) after pleural fluid testing.

She developed a normocytic anaemia with low iron, so was started on ferrous sulfate. Her symptoms and biochemical inflammatory picture had largely resolved after 4 days of intravenous antibiotics and she was converted to oral antibiotics with discharge planning.

Investigations

Unfortunately, her fevers and chest pain recurred shortly following her initial improvement and her CRP rose from 65 to 250 mg/dL, with radiation of the pain to her left arm. She was considered to have a slowly resolving pneumonia, transferred to the respiratory ward and antibiotics were changed to cover atypical organisms (teicoplanin and ciprofloxacin) after discussion with microbiology. Six blood culture samples had failed to grow any organisms and her pro-calcitonin was unremarkable (0.11 ng/mL). She had also developed abdominal pain and, given her deranged liver function tests, had an USS abdomen, which was normal. She was started on lansoprazole for presumed gastritis.

Her symptoms and fever continued, although intermittently. The length of her admission and uncertainty of diagnosis had affected the patient’s mood and she was started on sertraline. Further investigations were as follows (significant results are in italics):

• Infective

  • Urine pneumococcal/legionella antigen: negative
  • Pleural histology: lymphocytes/macrophages, no malignancy
  • Malaria/HIV/rickettsia/leptospirosis/dengue: negative
  • Lyme/coxiella/hepatitis A,B,C,E: negative
  • Echocardiogram: no signs of endocarditis
  • MRI spine: incidental haemangioma only
  • Bronchoscopy: normal
• Inflammatory

  • Erythrocyte sedimentation rate(ESR): 101 mm/hour
  • Ferritin: 463 ng/mL
  • perinuclear anti-neutrophil cytoplasmic antibodies: positive by fluorescence only (PR3 +myeloperoxidase negative)
  • Anti-DNA/CCP/ANA, rheumatoid factor, electrophoresis, haptoglobin: normal
  • Isolated raised immunoglobulin (Ig) A
  • Magnetic resonance cholangiopancreatography (MRCP): normal
• Malignancy

  • Blood film: Rouleaux
  • Bone marrow biopsy: reactive changes
  • CT abdomen and pelvis: normal

Her symptoms settled, though with intermittent fevers continuing. As significant causes of intermittent fevers had been excluded, she was discharged, 26 days after initial presentation, with oral doxycycline and outpatient respiratory follow-up in 2 weeks.

However, she re-presented to A&E after only 10 days, with further pleuritic chest pain and fever. She had a CT pulmonary angiogram which was negative and discharged shortly after. She was admitted once again, predominantly with chest pain. Troponin was negative and treated for possible pericarditis. She was also started on a beta-blocker and a statin for possible angina. She was transferred to the respiratory ward, given her previous lengthy admission. The following day, 45 days after her first presentation, the diagnosis of FMF was suggested. The diagnosis was made by a doctor trained in Egypt, where the condition is more prevalent in the local population.

Differential diagnosis

• Inflammatory

  • Vasculitis
  • Pericarditis
  • Connective tissue diseases: systemic lupus erythematosus, rheumatoid arthritis
  • Primary amyloidosis
  • Systemic auto-inflammatory disease (SAIDs)

    • Hyperimmunoglobulinaemia D syndrome
    • FMF
    • Adult-onset Still’s disease
• Infective

  • Common: empyema, atypical pneumonia, HIV/hepatitis
  • Less common: TB, lyme disease, malaria/dengue

• Malignancy: lymphoma, leukaemia

• Vascular: pulmonary embolism

Treatment

She was seen on the ward by rheumatology, who reviewed her history. Although she was of Ashkenazi Jewish heritage, her father may have had a Sephardic tanning pattern. Since our patient’s initial admission, her sister had developed eosinophilia and a pericardial effusion. They had both had posterior knee pain in childhood. On examination, our patient had developed some pain in the small joints of the hands and elbows. During her initial admission, she met criteria for both the commonly used diagnostic criteria for FMF (see below).

She was started 500 μg colchicine twice daily for her presumed diagnosis of an unspecified form of periodic auto-inflammatory fever, though vasculitis remained a differential. She had improvement of her symptoms over the next few days and was successfully discharged from hospital, with follow-up by rheumatology in clinic.

Outcome and follow-up

Around a month after discharge, the patient had run out of colchicine 48 hours prior to her rheumatology clinic appointment. In this context, she developed relapsing arthralgia, breathlessness and fatigue within 24 hours of stopping the drug. Her symptoms resolved and were well controlled when colchicine was restarted in rheumatology clinic.

She was referred to the Periodic Fever Clinic at the National Amyloidosis Centre (NAC) in London. She had serial serum amyloid-A protein levels on colchicine, but was not willing to stop colchicine to test for relapse, as suggested in clinic. Results ranged from 10 to 24 mg/L (see table 1), where normal levels are <10 mg/L in 96% of the population, over the course of a few months. These results were the results correlated to her symptoms or flares.

Table 1.

SAA and CRP results on colchicine

Date	13/11/17	07/12/17	15/12/17	29/12/17	24/01/18	05/02/18	24/05/18
CRP (mg/dL)	2	1	2	2	12	3	2
SAA (mg/L)	11.2	12.3	12.1	14.4	23.4	12.6	11.1

CRP, C-reactive protein; SAA, serum amyloid-A.

FMF genetic testing showed no pathogenic mutations but heterozygous P369S/R408Q mutations on exon 3 of the MEFV gene. The significance of these genetic mutations with regards to FMF is currently unknown, as many patients have mutations without symptoms, suggesting incomplete penetrance. She remains well symptom controlled on colchicine and opted to be seen locally only, instead of attending NAC in London, due to moving house and various other stressors. Her monozygotic twin was also found to be positive for P369S.

Discussion

SAIDs, of which FMF is one, represent a broad spectrum of conditions with overlapping features which can present at a variety of ages. For example, Muckle Wells syndrome presents in infancy, whereas Schnitzler syndrome typically starts at 35–50 years of age.^{1 2} Of these, FMF is the only one with an increased incidence in Jewish populations, though typically non-Ashkenazis, as well as other ethnicities.¹ The Auto-inflammatory Alliance SAID database provides a useful source for comparing these conditions.³

FMF is most common in non-Ashkenazi Jews, Armenians, Arabs and Turks, though it has been seen in many countries and described in Italians.^{1 4} This explains the relevance of the patient’s possible Sephardic heritage. At least 80% of patients experience arthralgia, abdominal pain, constipation, nausea and vomiting, fever or myalgia and the majority have their first experience by 20 years of age.⁵ However, many systems can be affected including cardiopulmonary, cutaneous, abdominal, lymphatic and joints.¹ Blood results will often show raised CRP and ESR with leucocytosis and raised fibrinogen during flares, which can last for 12–72 hours.¹

FMF is typically caused by an autosomal recessive abnormality in the MEFV gene, on chromosome 16p13.3, though other genetic inheritance patterns exist. The P369S/R408Q mutation in exon 3 of the MEFV gene, as demonstrated in this case, has been shown to be associated with an incomplete FMF phenotype and, less frequently, a typical FMF phenotype.⁶ Homozygote P369S can be seen in asymptomatic Ashkenazi Jews and, indeed, was found in 2% Ashkenazi Jews in the USA in one study.⁷ This suggests that this mutation has incomplete penetrance. In a different study, P369S/R408Q mutation was carried in 1.9% of the control population.⁷ By comparison, although it was present in 3.7% of the FMF population, there was no significant difference between the groups. They found that patients with the mutation did not have typical FMF features, including response to colchicine. Considering this asymptomatic population with these mutation, this raises the possibility that there may be additional, unknown, genes contributing towards the pathogenesis of FMF. Furthermore, our patient’s symptoms developed at older age than is typical of FMF. There are cases of late-onset FMF described,⁸ which raises the possibility that there may be environmental triggers contributing towards the development of FMF.

As such, they concluded that symptomatic patients with the P369S/R408Q mutation should be considered to have mixed auto-inflammatory syndrome.

There are two different diagnostic criteria that can be used for FMF: the Tel-Hashomer criteria⁹ and the Livneh criteria.¹⁰ The Tel-Hashomer criteria diagnose FMF on the basis of two or more major criteria or one major plus two minor symptoms (see table 2). The Livneh criteria require one or more major criteria, or one minor criterion plus five or more supportive criteria, or one minor criterion plus the first five supportive criteria (see box 1). This female fulfils both diagnostic criteria for FMF, with criteria that she meets highlighted in italics.

Table 2.

The Tel-Hashomer criteria (those met by this patient are in italics)⁹

Major criteria	Minor criteria
Recurrent febrile episodes (pleuritis, peritonitis, synovitis)	Recurrent febrile episodes
Amyloidosis of AA type without predisposing disease	Erysipelas-like erythema
Favourable response to regular colchicine treatment	FMF in a first degree relative

FMF, familial Mediterranean fever.

Box 1. Livneh criteria (those met by this patient are in italics)¹⁰ .

Major criteria

Typical attacks:

1. Peritonitis

2. Pleuritis (unilateral) or pericarditis

3. Monoarthritis (hip, knee, ankle)

4. Fever alone

Minor criteria:

1. Incomplete attacks involving either the abdomen, chest or joints

2. Exertional leg pain

3. Favourable response to colchicine

Supportive criteria:

1. Family history of FMF

2. Appropriate ethnic origin

3. Age <20 years at disease onset

4. Features of attacks:

   1. Severe, requiring bed rest

   2. Spontaneous remission

   3. Symptom-free interval

   4. Transient inflammatory response with one or more abnormal test result(s) for either white blood count, erythrocyte sedimentation rate, serum amyloid A and/or fibrinogen

5. Episodic proteinuria/haematuria

6. Unproductive laparotomy or removal of white appendix

7. Consanguinity of parents

Colchicine is the mainstay of treatment as prophylaxis for flares. It acts as an anti-inflammatory agent by preventing the activation of neutrophils and leukotrienes, and by binding beta-tubulin to prevent spindle formation.¹¹ This can prevent flares and reduces risk of progression to AA amyloidosis. Over 50% of patients can develop secondary amyloidosis if untreated, demonstrating the importance of timely and closely monitored treatment.¹²

Given that our patient meets the diagnostic criteria, yet has presented at an atypical age and has no pathogenic mutations, there remains doubt as to the precise diagnosis. Considering this, mixed auto-inflammatory syndrome may be the more appropriate diagnosis.

Patient’s perspective.

Looking back at the unpleasant experience of being ill and not knowing the source of my condition made for a daunting time in hospital. The outstanding treatment I received from the doctors and staff at the Royal Lancaster Infirmary was truly amazing, not only were they so accommodating, but crucially they extensively tested every avenue known without hesitation. For which I thank them immeasurably, especially the doctor who raised the possibility of familial Mediterranean fever, having worked with this condition in patients back in his native Egypt.

I am so very, very grateful that this condition has been confirmed as it too has now given my biologically identical twin sister a potentially pain-free life having recently started on colchicine due to my diagnosis.

The diagnosis (in my case) of familial Mediterranean fever has potentially saved my twin sister’s life and mine, to which I am eternally grateful.

Learning points.

• To take a thorough history in patients with fever of unknown origin and include systemic auto-inflammatory disease as a less common differential in susceptible patients.

• To be aware of useful resources and appropriate referral centres for systemic auto-inflammatory diseases.

• To consider colchicine in patients with recurrent sterile fevers, while conducting appropriate investigations, in order to prevent amyloidosis.

• Genetic testing does not necessarily give the diagnosis—both clinical and genetic components of diagnosis are important in familial Mediterranean fever, as the role of the P369S/R408Q mutation in FMF remains unclear.