Coronal CT paranasal sinuses showing features of allergic fungal rhinosinusitis
MRI features: The high
protein and low water concentration of allergic fungal mucin coupled with high
water content within surrounding oedematous sinus mucosa gives rise to specific
T1 – Involved sinus
cavities demonstrate varying signal intensities. There is enhancement of periphery of the
involved sinuses due to mucosal Oedema
T2 – Hypo intensity
of signal within involved sinuses – due to dehydrated state of mucin
periphery of the involved sinus due to mucosal oedema
Estimation of IgE –
Total IgE values is elevated in AFRS. A
value of more than 1000 IU/ml is an indicator of AFRS activity.
RAST / ELISA Test –
Positive for bipolaris specific IgE and IgG antibodies. These patients show positive evidence of
characteristics of fungal mucin:
The production of
allergic mucin is pathognomonic of AFRS.
Grossly allergic mucin is thick, tenacious and viscous in
consistency. Its color may vary from
brown to dark green. It is only the
mucin rather than sinus mucosa that provides the relevant histological evidence
necessary to make the diagnosis of AFRS.
Examination of nasal mucosa / polypi shows evidence of chronic
inflammation. Eosinophils are also seen
in abundance. Pathologic examination of
these tissues is done to establish that fungal invasion is not present.
Histology of allergic
fungal mucin reveals the characteristic ranching non invasive fungal hyphae
within sheets of eosinophils and Charcot – Layden crystals. Classically H&E stains accentuate the
mucin and cellular components of allergic mucin but fail to stain the fungal
hyphae. Silver stains are specifically
used to stain fungal hyphae. Silver
stains color fungi black / dark brown.
Fungal culture: These tests atmost provide supportive
evidence. Diagnosis of AFRS is not based
on positive fungal cultures from mucin.
Treatment: Still evolving. Previously it used to be radial surgery. Now a combination of conservative surgery in
combination with adjunct medical therapy is becoming popular.
The goal of any
surgical procedure is to eradicate all allergic mucin while providing permanent
drainage and ventilation for the affected tissues.
Even in the best of hands the incidence of
AFRS recidivism is very high when treated with surgery alone. Adjunctive medical therapy should also be
tried to get over this problem. Fungal
immunotherapy and immunomodulation is becoming popular these days.
Role of steroids is
limited only to postpone the surgery.