What are the symptoms of familial Mediterranean fever (FMF)?

Symptoms of Familial Mediterranean Fever

Familial Mediterranean fever presents with recurrent attacks of fever and serosal inflammation, most commonly manifesting as abdominal pain, fever, chest pain, and arthritis/arthralgia, with attacks typically lasting less than 72 hours. 1

Core Clinical Manifestations

The hallmark presentation of FMF consists of stereotyped, self-limited inflammatory attacks with the following features:

Primary Attack Symptoms

• Abdominal pain - The most common symptom, occurring in 62-90% of patients 2, 3

  • Presents as acute peritonitis-like pain
  • Can mimic surgical abdomen

• Fever - Present in approximately 66% of patients during attacks 3

  • Important caveat: About 10% of FMF patients have attacks WITHOUT fever 4
  • These afebrile patients tend to have later age of onset and predominant musculoskeletal symptoms
  • Fever may not be documented at clinical presentation even when present during attacks (only 19.6% had documented fever at presentation in one cohort) 2

• Musculoskeletal involvement - Occurs in 75-76% of patients 3

  • Arthralgia and/or arthritis
  • Exercise-induced leg pain
  • Myalgia
  • More prominent in patients with afebrile attacks 4

• Chest pain - Affects 52-66% of patients 3

  • Due to pleuritis or pericarditis
  • Represents serositis of thoracic cavity

Additional Manifestations

• Erysipelas-like rash - Erythematous skin lesions, typically on lower extremities
• Scrotal involvement - In males, due to tunica vaginalis inflammation

Attack Characteristics

Duration: The vast majority of attacks last less than 72 hours 2

• Approximately two-thirds of patients have attacks lasting less than 48 hours
• Only 6% experience attacks longer than 72 hours
• Attacks are recurrent and stereotyped in nature

Pattern: Episodes are self-limited with complete resolution between attacks, accompanied by elevated acute phase reactants during attacks 1

Age of Onset

• Median symptom onset typically occurs around age 4-10 years 3, 4
• Most patients are diagnosed clinically above age 2 years
• Critical exception: FMF can present as early as the neonatal period (first month of life) 5
  • Neonatal cases may present with isolated recurrent fever
  • Often misdiagnosed as late neonatal sepsis or occult bacteremia
  • Earlier onset cases (before age 2) tend to have more severe disease course

Atypical Presentations to Recognize

1. Afebrile FMF (approximately 10% of cases) 4:

   • Later age of onset (median 7 years vs. 4 years)
   • Predominance of musculoskeletal symptoms
   • May be diagnosed earlier due to early referral to rheumatology

2. Isolated fever in infants: Can be the sole presenting symptom, particularly in very young children 5

Laboratory Findings During Attacks

• Increased acute phase response 1
• Elevated inflammatory markers (though serum amyloid A may be normal in 47.5% at initial presentation) 2
• Markers normalize between attacks in well-controlled disease

Long-term Complications if Untreated

AA amyloidosis represents the most severe complication of chronic untreated inflammation 1, though rates vary by population and mutation type. This underscores why recognizing symptoms early is critical for initiating colchicine therapy to prevent this irreversible complication.

Clinical Pearls for Recognition

• Think FMF in patients from Mediterranean ancestry (Turkish, Armenian, Arab, Sephardic Jewish populations) 2, 3
• Parental consanguinity (present in ~25% of cases) and positive family history (present in ~33% of cases) increase suspicion 2
• The triad of recurrent fever + abdominal pain + inflammatory markers in a child from endemic areas should immediately raise FMF as a diagnostic possibility 6
• Don't exclude FMF based on absence of fever alone - consider musculoskeletal-predominant presentations 4