Answer:
Dear
Larry,
Because
of the variation in clinical presentation and a lack of a specific
diagnostic finding on histopathology, a uniformly accepted definition
of parapsoriasis remains lacking.
There
are 2 general forms: a small plaque type, which is usually benign,
and a large plaque type, which is a precursor of cutaneous T-cell
lymphoma (CTCL).
Treatment
of small plaque parapsoriasis is unnecessary but can include emollients,
topical tar preparations or corticosteroids, and/or phototherapy.
Treatment
of large plaque parapsoriasis is phototherapy or topical corticosteroids.
The duration
of parapsoriasis can be variable. Small plaque disease lasts several
months to years and can spontaneously resolve. Large plaque disease
is chronic, and treatment is recommended
because it may prevent progression to CTCL.
No definitive
studies have been published regarding therapy of parapsoriasis. When
treated, most patients are initiated empirically on topical steroids
or phototherapy. Typically, patients will have partial responses and/or
relapse off any therapy.
A rational
therapeutic strategyfor parapsoriasis is lacking because there are
no longitudinal studies that correlate treatment response and impact
on progression to CTCL.
Bexarotene,
a resinoid, a subclass of retinoids that binds preferentially to nuclear
retinoic X receptors (RXR), has therapeutic activity in CTCL.
Bexarotene
1% gel has been approved for treatment of CTCL and found to have up
to a 63% response rate in Stage Ia to IIa CTCL.
Psoralen
and long-wave ultraviolet light A (PUVA) shows promise in managing
and eliminating large plaque parapsoriasis. The therapy is most effective
in conjunction with radiation during the earliest stages of disease.
A study
conducted by the Department of Dermatology, Sahlgrenska University
Hospital in Göteborg, Sweden, found that PUVA combined with limited
radiation generated remission in 22 of the 24 patients involved in
the study.
The patients
who had only LPP (Large plaque parapsoriasis) that hadn't progressed
to skin cancer maintained remission for at least 18 years with one
treatment.
Those
who had developed mycosis fungoides (first-stage CTCL) required multiple
treatments, but their disease didn't progress and remission lasted
three to 18 years. Two patients with advanced CTCL died during the
study.
Side
effects of PUVA include nausea, vomiting, itching and skin irritation
at the treatment site.
Narrow
band (311 nm) ultraviolet B (NB-UVB) phytotherapy are safe and effective
to manage SPP (Small plaque (digitate) parapsoriasis). Researchers
at the Department of Dermatology, University of Munich, Germany, used
NB-UVB to treat 16 patients with SPP in 1996.
Initial
remission lasted approximately 29 weeks, but after an average of 32
treatments, all patients had full remission.
NB-UVB
has fewer side effects than PUVA and is the preferred method for treating
SPP (Small plaque (digitate) parapsoriasis) when steroids prove ineffective
or there are multiple lesions
