Complexity in unclassified auto-inflammatory disease: a case report illustrating the potential for disease arising from the allelic burden of multiple variants

A Case of Protracted Febrile Myalgia Syndrome with Atypical Course and Severe Asymmetric Loss of Muscle Strength

Protracted febrile myalgia syndrome (PFMS) is a rare form of familial Mediterranean fever (FMF) characterised by prolonged myalgia. The duration of PFMS is much longer than a typical 2-5-day attack familial Mediterranean fever and lasts for 2-6 weeks until they treated with corticosteroids. Colchicine is not effective for control of PFMS's attacks. The attacks typically resolve with corticosteroid and/or IL-1 receptor blockers. Herein, we present a young adult without typical familial Mediterranean fever clinical features but presenting with atypical course and severe asymmetric muscle strength loss. Thigh magnetic resonance imaging confirmed inflammation and oedema and muscle biopsy showed no pathological findings. Electromyography revealed myopathic findings during attack-period, despite normal results in attack-free study. The patient was treated successfully with anakinra and remarkable rapid recovery in both muscular findings and acute phase reactants were observed. PFMS should be considered even in the absence of apparent FMF attack pattern and in the presence of unexpected severe muscle weakness, especially in areas endemic for FMF and long-lasting myalgia attacks.

Off-label use of canakinumab in pediatric rheumatology and rare diseases

Since the first success of interleukin-1 blockade in cryopyrin-associated periodic syndrome, the use of interleukin-1 inhibitors has expanded to other disorders, including off-label indications. In particular, canakinumab has been employed in an off-label fashion in several diseases such as rare monogenic autoinflammatory diseases and multifactorial autoinflammatory diseases, disclosing an excellent efficacy and good safety profile in pediatric patients unresponsive to standards of care. In addition, hyperferritinemic syndromes and complex disorders, as well as Kawasaki disease, uveitis, and other pediatric rare disorders, represent additional areas where canakinumab efficacy is worth exploring. Altogether, the results summarized below are of paramount importance in pediatric patients where a considerable proportion of treatments are prescribed off-label. This review focuses on the off-label use of canakinumab in pediatric patients affected by systemic immune-mediated diseases.

A 9-Year-Old Patient with Recurrent Fever, Urticarial Rash and Demyelinating Brain Lesions: NLRP3-Autoinflammatory Disease in Ecuador

Autoinflammatory diseases (AIDs) are a relatively new family disorders defined approximately 20 years ago. AIDs are caused by defect(s) or dysregulation of the innate immune system, characterized by recurrent or continuous inflammation and lack of a primary pathogenic role for the adaptive immune system. One AID, NLRP3-associated autoinflammatory disease (NLRP3-AID), involves a clinical presentation since the neonatal period or childhood, with multiple inflammatory recurrent symptoms that appear throughout the patient´s life. We present the first case of NLRP3-AID in Ecuador. The patient presented recurrent fever since 6 months of age associated with urticarial rash, arthralgias, and abdominal pain; recently, he had a seizure at 7 years of age. Brain MRI revealed demyelinating lesions, and genetic testing uncovered a de novo mutation in the NLRP3 gene. The patient had a good clinical response to treatment with canakinumab.

Anti-Myelin Oligodendrocyte Glycoprotein Encephalomyelitis and Extensive Longitudinal Transverse Myelitis Associated with Compound Heterozygous NLRP3 Missense Mutations in a Young Child

Acute disseminated encephalomyelitis in association with extensive longitudinal transverse myelitis is reported in a young child with positive anti-myelin oligodendrocyte glycoprotein (MOG) antibody with heterozygous NLRP3 missense mutations; p.(Arg488Lys) and p.(Ser159Ile). This case may well present an exceptional coincidence, but may describe a yet unrecognized feature of the spectrum of childhood onset cryopyrinopathies that contribute to the understanding of the genetic basis for anti-MOG antibody positive encephalomyelitis. Based on this observation, a larger scale study investigating the role of NLRP3 and other inflammasomes in this entity would provide important pathophysiological insights and potentially novel avenues for treatment.

Colchicine - an effective treatment for children with a clinical diagnosis of autoinflammatory diseases without pathogenic gene variants

BACKGROUND

Autoinflammatory diseases (AID) are rare chronic conditions with high disease burden, affecting children and adults. Clinically and genetically confirmed, AID can be effectively treated with targeted cytokine inhibition. In contrast, for patients with clinical AID symptoms without pathogenic gene variants, no treatment recommendations are available. Colchicine is approved and established as effective, safe and low-cost first-line therapy in Familial Mediterranean Fever. Up to now, efficacy data for colchicine in children with a clinical AID diagnosis without pathogenic gene variants are rare. This pilot study was performed to evaluate the effectiveness of colchicine in children with a clinical diagnosis of AID without pathogenic gene variants.

METHODS

A pilot cohort study of consecutive children with active clinical AID without pathogenic gene variants treated with colchicine monotherapy was performed between 01/2009 and 12/2018. Demographics, clinical and laboratory characteristics were determined serially. Colchicine dosing and safety were documented. Physician estimate of disease activity was captured on visual analogue scales (VAS).

PRIMARY OUTCOME

Complete response (PGA ≤2 plus CRP ≤0.5 mg/dL and/or SAA ≤10 mg/L) at last follow-up.

SECONDARY OUTCOMES

partial/no response, flare characteristics and requirement for rescue therapies.

ANALYSIS

Nonparametric comparison of disease activity measures.

RESULTS

A total of 33 children were included; 39% were female. Median age at colchicine start was 3.8 years, median follow-up was 14.1 months. Clinical AID diagnoses included CAPS (24%), FMF (27%), PFAPA (43%) and unclassified AID (6%). At baseline, overall disease activity was moderate (PGA 4), inflammatory markers were elevated (CRP 12.1 mg/dL; SAA 289.2 mg/L), and 97% reported febrile flares.

OUTCOME

55% achieved complete response, 35% showed partial response and 58% had no febrile flares at last follow-up. Inflammatory markers (SAA: p < 0.0001, CRP: p < 0.005) and disease activity (p < 0.0001) decreased significantly. Overall, 93% of children experienced improvement of flare characteristics.

CONCLUSION

Colchicine was found to be effective and safe in children with a clinical AID diagnosis in the absence of pathogenic gene variants. Colchicine is a low-cost treatment option for non-organ threatening AID.

Successful treatment of refractory hyperferritinemic syndromes with canakinumab: a report of two cases

BACKGROUND

Hyperferritinemic syndromes are systemic inflammatory disorders characterized by a dysfunctional immune response, which leads to excessive activation of the monocyte-macrophage system with hypercytokinemia and may pursue a rapidly fatal course.

CASE PRESENTATION

We describe two patients of 11 and 9 years of age with hyperferritinemic syndromes, one with impending macrophage activation syndrome (MAS) and one with overt MAS, who were refractory or intolerant to conventional therapies, but improved dramatically with canakinumab.

CONCLUSIONS

Our report indicates that canakinumab may be efficacious in the management of hyperferritinemic syndromes, including MAS.