infusion.
Discussion: This case enhances our current understanding of interfer-
onopathies. Although the phenotype and course of the disease is com-
patible with SAVI3, genetic testing is negative to date. Presently there
are eleven heterozygous gain-of-function (GoF) variants for SAVI4. With
JAK inhibition as the most successful therapeutic option to date5. Our
case possibly represents an as yet unreported genetic variant, further
studies are awaited.This case enhances our current understanding of
interferonopathies. Although the phenotype and course of the disease
is compatible with SAVI3, genetic testing is negative to date. Presently
there are eleven heterozygous gain-of-function (GoF) variants for
SAVI4. With JAK inhibition as the most successful therapeutic option to
date5. Our case possibly represents an as yet unreported genetic var-
iant, further studies are awaited.This case enhances our current under-
standing of interferonopathies. Although the phenotype and course of
the disease is compatible with SAVI3, genetic testing is negative to
date. Presently there are eleven heterozygous gain-of-function (GoF)
variants for SAVI4. With JAK inhibition as the most successful therapeu-
tic option to date5. Our case possibly represents an as yet unreported
genetic variant, further studies are awaited.
Key learning points:
• Early suspicion for an interferonopathy in very young infants with

interstitial lung disease
• Expanding the potentially new genetic variants of this condition
• Challenge of treatment management

Abstract citation ID: rkae117.026
OA26 ATYPICAL MULTISYSTEM INFLAMMATION RELATED TO
INFECTION OR JUST PLAIN OLD POLYARTERITIS NODOSA?

Enas Alyaldin1, Peter Bale2

1Mid and South Essex NHS Foundation Trust, Basildon, United
Kingdom, and 2Cambridge University Hospital NHS Foundation
Trust, Cambridge, United Kingdom

Introduction: We present the case of a 5-year-old boy with episodes
of pyrexia of unknown origin associated with polyarthritis, central neu-
roinflammation and mucocutaneous manifestations. His skin biopsy
demonstrated a nodular vasculitis which could be consistent with poly-
arteritis nodosa. Interestingly though, he had additional atypical rashes,
ocular inflammation and evidence of acute and past streptococcal
infection and his fever and CRP normalised prior to corticosteroid initia-
tion.
Case description: A five-year-old British African male presented with
five-week history of persistent fever, headaches, joint pain and bilateral
eye pain. He was transferred to a tertiary paediatric infectious disease’s
unit due to unrelenting fever with no fixed pattern, despite nine days of
broad-spectrum intravenous antibiotics. He was diagnosed with neu-
roinflammation of uncertain aetiology, evidenced by leptomeningeal
enhancement and bilateral papillitis on brain MRI. CSF microbiology
and autoimmune profiles were negative. There was no evidence of pri-
mary malignancy. The fever resolved with pulsed IV methylpredniso-
lone and the child was discharged home on a weaning regime of oral
prednisolone. After stopping steroid treatment, he represented with
high-grade fever, limping, anterior uveitis and new-onset non tender
cutaneous lesions, plaques over eyelids and cheek and annular lesions
over arms, legs and buttocks. Repeat MRI of the brain and spine
showed resolution of previous neuroinflammation.
Blood tests revealed raised ANA, IgG and ASOT titre, and his throat
swab was positive for Group A Streptococcus. He completed 10 days
of intravenous antibiotics and oral high dose ibuprofen (10 mg/kg TDS).
On review by tertiary paediatric rheumatology, he was identified to
have pleomorphic skin rash and subcutaneous nodules. Skin and deep
tissue biopsy confirmed lobular and septal panniculitis with necrotising
vasculitis, consistent with a nodular vasculitis. Treatment with high-
dose steroid and mycophenolate mofetil (MMF) was initiated, but his
CRP and fever had resolved prior to his first dose. He experienced
improvement in systemic symptoms and arthritis; however, skin lesions
persisted, with appearance of new lesions and hyperpigmentation, on
reduction of steroid dose. His course was complicated by acute vari-
cella infection, requiring oral aciclovir. Further treatment trials included
topical tacrolimus and topical corticosteroids for his skin lesions. At
one biopsy site, he experienced significant delay in wound healing. The
genetic panel for primary immunodeficiency panel (R15) demonstrated
no pathological variants.
Discussion: This case report highlights that, whilst the biopsy may be
consistent with nodular vasculitis, such as PAN, the clinical

manifestations are not perfectly aligned. Discussion within the rheuma-
tology community would support optimal patient care.
Childhood-onset Polyarteritis Nodosa (c-PAN) is a rare systemic vas-
culitis. Although the aetiology is unknown, associations with infections
like group A streptococcus and hepatitis B suggest a postinfectious
autoimmune response. There are no clear genetic links to PAN, but
PAN-like vasculitis is part of reported monogenic autoinflammatory
conditions.
Key atypical features in this case include uveitis at presentation, non-
specific central neuroinflammation, unusual cutaneous lesion morphol-
ogy, improvement of acute phase reactants before immunomodulatory
treatment, and delayed biopsy wound healing. While ocular findings in
PAN may include episcleritis, scleritis, keratitis, retinal vascular occlu-
sions, and ocular ischemic syndrome, uveitis has not been reported in
c-PAN.
The patient also showed nonspecific inflammatory changes on initial
MRI. Neurological involvement in c-PAN typically includes cerebrovas-
cular accidents, cranial nerve palsies, and mononeuritis multiplex, with
meningeal involvement being less common (reported 4% in a study of
69 children). Additionally, the patient experienced delayed wound heal-
ing following the biopsy, which is undocumented in c-PAN, but may be
related to immune modulating treatment.
A positive streptococcal throat swab could suggest an immune reac-
tion as part of bacterial tonsilitis, or Acute Rheumatic Fever. However,
he did not meet Jones Criteria, there was no response to prolonged
antibiotics and the chronic remitting nature made these less likely.
An autoinflammatory disorder, Deficiency of Adenosine Deaminase 2
(DADA2), was also considered but he had no evidence of livedo race-
mosa, strokes and no CECR1 mutation was identified.
Our case has been discussed within a multidisciplinary team and we
speculate that it could represent a previously undefined immune sensi-
tivity within the autoimmune, autoinflammatory and immune deficiency
spectrum giving an exaggerated response to infection.
Key learning points:
• This case presents a significant diagnostic challenge due to its

atypical clinical features and inconclusive extensive investigations,
including immunologic testing, tissue biopsy, and genetic analysis.

• While the patient’s symptoms improved with high-dose steroids
and MMF, the recurrence of symptoms upon tapering steroids
underscores the persistent inflammatory nature of the disease.

• The detection of group A Streptococcus in the patient’s throat swab
suggests a potential postinfectious autoimmune trigger, highlight-
ing the role infections can play in the pathogenesis of vasculitis. The
negative results from the R15 Primary Immunodeficiency panel sug-
gest that more advanced genetic and immunologic testing may be
beneficial.

• We invite discussion on whether additional genetic or immunologic
testing could optimise this patient’s care and contribute to the
broader understanding of atypical vasculitis syndromes.

Abstract citation ID: rkae117.027

children. Our patient had a peripheral arterial thrombus with no risk fac-
tors apart from a background of recurrent Henoch-Schönlein Purpura
(HSP). He had no history of trauma. Thrombosis as a complication of
HSP is extremely rare with onlyeight case reports so far in children and
among those eight, there is only one resembling our case with an arte-
rial thrombus. We considered other causes of thrombosis and
screened our patient for thrombophilia, infection and malignancy.
Case description: Our patient, a 12-year-old boy with a background
of recurrent HSP for the last two years, presented with a rash on the left
2nd toe followed by blackish discolouration of the distal part of the
same toe, a few days later.
His initial presentation with purpuric rash, arthralgia, and abdominal
pain was diagnosed as HSP and he required no intervention required
for this. He continued to have regular flares of his HSP every six weeks,
and these were self-limiting. His last flare was in February 2024.
In April 2024, his feet appeared dusky and mottled. He presented to his
local hospital with a rash on the tip of his left 2nd toe which turned gan-
grenous. He was otherwise systemically well. He was initially treated
with antibiotics and acyclovir as a swab from the lesions grew

i18 https://academic.oup.com/rheumap

ORAL ABSTRACT PRESENTATIONS