DISCUSSION
Pyoderma gangrenosum is a rare inflammatory skin disorder occurring most
commonly between 20-50 years of age11 with females
comprising of 59–76% of cases.12 PG is clinically
classified into 4 types, i.e., ulcerative, bullous, pustular and
vegetative types. Ulcerative PG is the most common type that is
characterized by appearance of small follicular pustules appear
initially that rapidly forms abscess and ulcerates. These ulcers enlarge
rapidly to form irregular ulcers undermined edge, raised edematous and
violaceous borders with necrotic tissues and scanty discharge on floor.
The most frequently involved site of PG is the lower legs; however, any
other sites can also be involved. 11
PG is associated with other diseases in 33–50% of
cases.1,2 The most frequent disease associations
include Inflammatory Bowel Disease (IBD) present in 20–30% of cases.
Rheumatoid arthritis and other seronegative arthritis’s occur in about
10% of cases, hematological malignancy or monoclonal gammopathy in
approximately 5% and other visceral malignancies in
5%.7,11 The association of pyoderma gangrenosum with
psoriasis and psoriatic arthritis has been found to be approximately
10%.7
Palmoplantar pustulosis is a chronic inflammatory dermatosis
characterized by erythematous and scaly plaques studded with sterile
pustules on the palms and/or soles. It occurs most commonly between the
ages of 30 and 50 years 12with a female predominance
ratio of 5:1.13 The associated nail changes are seen in 30-76% of cases
of PPP. The most common finding are onycholysis, followed by pitting and
destruction of the nail. The other nail changes include scale, subungual
hyperkeratosis, subungual pustulation, indention, transverse and
longitudinal ridging, curvature abnormalities, discoloration, splinter
hemorrhage, and thickening of the nail.14 In our
patient yellowish discoloration, distal onycholysis and a few pits were
found in all most all nail plates of bilateral hands and feet and
subungual hyperkeratosis in the great toes.
Palmoplantar pustulosis is most commonly associated with psoriasis and
or psoriatic arthritis in 24-84.21% of cases followed by autoimmune
thyroid disease in 20-40% of cases and it is the commonest cutaneous
manifestation of SAPHO syndrome (synovitis, acne, pustulosis,
hyperostosis and osteitis).3,15 Approximately 10% of
patients with palmoplantar pustulosis suffer from osteoarticular
symptoms, termed pustulotic arthro-osteitis (PAO), which most commonly
affects the stern costoclavicular joints, followed by the spine and
sacroiliac joints.10
The pathogenesis of both palmoplantar pustulosis remains unclear but
they are considered as a spectrum of common disorder involving several
common cytokines such as tumor necrosis factor-a (TNF-α), interleukin
(IL)-17 and (IL)-23 and share a common histological feature of
neutrophilic infiltration.3,4,5 Recent studies have
demonstrated that TNF-a, IL-17 and IL-23 are increased in lesional skin
of PG.4,5,6 Upregulation of TNF-a, IL-17 and IL-23 also have been
observed in PPP skin samples. In 2014, Ohtsuka and Yamamoto observed
IL-17-positive lymphocytes in both of the biopsy samples obtained from a
leg ulcer and plantar pustule.10 These findings
suggest that the T-helper (Th) 17-associated cytokines may play crucial
roles in both PG and PPP. Many patients with PG as well as PPP responded
well to biologic agents such as anti-TNF-a and anti-IL-12/23p40
antibodies.16,17
Although association between plaque psoriasis and psoriatic arthritis is
observed, co-existence of PG and Palmoplantar pustular psoriasis (PPP)
is rarely reported in literature. Occurrence of multiple
autoinflammatory diseases simultaneously in one patient has been the
subject of several reports. This phenomenon may result from similar
etiologic pathways involved in the development of the autoinflammatory
conditions. Similarly, coexistence of PG and PPP may be implicated by
similar etiopathogenesis of both conditions. Only five cases have been
reported till date in Japanese population and our is the 6th case in the
literature and first case report from Nepal. The genetic predisposition
may influence the susceptibility of PG and PPP; however, the genetic
background of PPP is complex. There may be some ethnic association and
may be similarities between Japanese and ours case, but we were not able
to do the genetic study. Certain stimuli are required to provoke PG. In
all 5 reported cases, PPP was preceded 1month to 30 years to give rise
to the onset of PG lesion.10 In our case also, the lesions of PPP
developed 4months prior to the development of PG lesion. PPP may be a
triggering factor for PG and active lesions of PPP is needed for the
occurrence of PG. Like in our case, PPP and PG recurred after the
stopping of the oral prednisolone.
The first line of treatment of PG is systemic corticosteroids. However,
for the refractory cases, other immunosuppressive and immunomodulatory
drugs, such as cyclosporine, azathioprine, methotrexate, thalidomide,
tacrolimus, mycophenolate mofetil, and recently biologics are also used.
Methotrexate has been found to reduce the neutrophil chemotaxis,
suggesting a role for its use in pyoderma gangrenosum. However no
therapeutic standards have been established for controlling PPP. Various
treatments including methotrexate have been used to treat. The patient’s
condition may be well controlled with low-dose regimen of methotrexate.
It may be effective in the treatment of nail complications, reduce the
serious adverse effects of corticosteroid, cheaper than retinoid and
azathioprine. Therefore, we gave in our patient a short duration of oral
prednisolone and maintained with the low dose of methotrexate with good
response to prevent the recurrence of the conditions and hoping to get a
good response in nail changes of PPP.
In conclusion, PG and PPP share the common pathogenesis with
histological features, common age group and female preponderance suggest
a common etiological link. Further research is required to ensure the
etiological relationship between PG and PPP.
Acknowledgments :
The authors would like to acknowledge Dr. Muna Bista who reviewed
manuscript for intellectual content and aided in submission of Journal.
Conflict of interest : none
Funding Source : none