Case report
This case report describes a familial cluster involving a 33-year-old
Iranian woman and her two children, a 13-year-old daughter and an
8-year-old son, who presented with similar clinical manifestations.
The mother was admitted to our medical facility, presenting with a
3-week history of persistent fever and arthralgia affecting both ankles
and knees. Additionally, she exhibited symmetrical, multiple, round,
light pink, tender erythematous nodules with indistinct borders over the
pretibial skin (Figure 1). The patient reported a preceding episode of
respiratory symptoms, including cough, pharyngitis, fever, and
lymphadenopathy, occurring 4 weeks prior to the onset of the skin
lesions. Notably, there was no history of recent medication use, travel,
COVID-19 vaccination, or exposure to individuals with infectious
illnesses prior to the onset of symptoms.
One week after the mother’s respiratory symptoms began, her two children
developed similar respiratory manifestations, including cough,
pharyngitis, and fever. The daughter presented to our medical facility
with a 3-day history of erythematous, tender nodules on her lower
extremities. Physical examination revealed multiple, symmetric,
erythematous, tender nodules measuring roughly 1.5 cm in diameter on the
pretibial aspects of both lower legs. The lesions were similar in
appearance to those observed in her mother’s case. No evidence of motor
deficits or sensory abnormalities was noted, and distal pulses were
palpable and symmetric. The patient reported mild discomfort during the
examination of her ankles and knees. Systemic examinations were
unremarkable, with no signs of mucous membrane involvement or
lymphadenopathy.
The son presented with a 4-day history of similar erythematous, tender
nodules on his lower extremities. Physical examination findings were
comparable to those of his mother and sister, with multiple, symmetric,
erythematous, tender nodules measuring approximately 1 cm in diameter on
the pretibial aspects of both lower legs. No motor deficits, sensory
abnormalities, or impairment of distal pulses were noted. The patient
reported mild discomfort during the examination of his ankles and knees.
Systemic examinations were unremarkable, with no evidence of mucous
membrane involvement or lymphadenopathy.
Laboratory investigations were conducted for all three patients,
including complete blood counts, renal and hepatic function tests,
antistreptolysin O (ASO) titers, erythrocyte sedimentation rates (ESR),
and C-reactive protein (CRP) levels. The mother’s white blood cell count
was elevated at 11,000 cells/μL, consistent with leukocytosis. Her ASO
titer was significantly increased at 333 IU/mL, suggestive of a recent
streptococcal infection. The daughter’s white blood cell count was
mildly elevated at 9,500 cells/μL, and her initial ASO titer was
significantly elevated at 1067.6 IU/mL. A repeat test yielded a result
of 327 IU/mL, still above the normal upper limit. The son’s initial ASO
titer was within the normal range at 31.2 IU/mL; however, due to
persistent symptoms, a repeat test was performed, revealing an elevated
value of 100 IU/mL. All three patients had mildly elevated ESR and CRP
levels, indicating the presence of underlying inflammation. Renal and
hepatic function tests were within normal limits for all patients.
Imaging studies, including chest radiographs, were performed for all
three patients and showed no abnormalities. Polymerase chain reaction
(PCR) tests for COVID-19 were also conducted, and the results were
negative.
The constellation of clinical findings, including the characteristic
erythematous nodules on the lower extremities and the preceding
respiratory symptoms, along with the laboratory abnormalities,
particularly the elevated ASO titers and inflammatory markers, strongly
support the diagnosis of EN secondary to a recent streptococcal
infection in this familial cluster. The temporal relationship between
the mother’s and her children’s respiratory symptoms and subsequent
development of erythematous nodules suggests a shared environmental
exposure to the streptococcal pathogen.