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