Crohn disease is a chronic granulomatous inflammatory bowel disorder that may involve any segment of the gastrointestinal tract.

Extraintestinal manifestations including ocular findings, musculoskeletal pathology, and Mucocutaneous manifestations.Mucocutaneous findings are the most frequent extraintestinal manifestation 22% to 44% of patients present with changes categorized as granulomatous skin disease, oral manifestations, cutaneous changes secondary to nutritional deficiencies, and cutaneous disorders that have been associated with Crohn disease (eg, pyoderma gangrenosum, erythema nodosum, erythema multiforme, and epidermolysis bullosa acquisita).

Perianal, peristomal,and perifistular inflammatory lesions most common cutaneous manifestations lesions Parks et al - the first to describe the presence of sterile, noncaseating, granulomatous lesions of the skin at sites noncontiguous with the gastrointestinal tract in patients with Crohn disease. This entity is known as metastatic Crohn disease (MCD), the name first coined in 1970 by Mountain.

Metastatic Crohn disease is defined as granulomatous lesions of the skin occurring at sites separate from the gastrointestinal tract in patients affected with Crohn disease. In adults, age of onset - 29 to 39 years. Majority of patients have a previous diagnosis of Crohn disease.

Up to one third of MCD patients have active gastrointestinal symptoms. Twenty percent of patients with MCD may present without classical manifestations of Crohn disease. In these patients, Crohn disease manifests in 2 months to 4 years after the initial presentation of MCD.

Cutaneous lesions of MCD may present as papules, plaques, nodules,and ulcerations, which may involve the arms, legs, genitalia, and face. Predilection for the moist environment of skin folds, including submammary and abdominal creases perineal and inguinal regions present as a solitary lesion or occur in multiple sites painless or tender upon palpation.

Left submammary crease ulcer with well-defined border exuding purulent fluid.

In the pediatric population, ages of 10 to 14 50% of these patients having concurrent Crohn disease. In children who present with MCD lesions without Evidence of Crohn disease, subsequent onset of gastrointestinal manifestations occurs from 9 months to 14 years after the initial presentation of MCD.

The genitalia appear to be the most common area of involvement; most common cutaneous manifestation presents as labial, penile, and/or scrotal swelling with or without accompanying erythema. Genital ulcerations have also been reported.

Males = females Although Crohn disease typically affects the terminal ileum more often than the large bowel, cutaneous manifestations of Crohn disease appear to occur more often in patients who have involvement of the colon

Presents as sterile, noncaseating granulomatous inflammation located primarily in the superficial papillary and deep reticular dermis with occasional extension into the subcuticular fat. The granulomas consist of Langerhans giant cells, epithelioid histiocytes, lymphocytes, and occasional plasma cells.

Perivascular granulomatous inflammation surrounding the dermal vessels. Necrobiosis consisting of collagen degeneration accompanied by granulomatous inflammation. Eosinophils may also present.

Low-power image of left submammary crease ulcer withunderlying noncaseating granulomatous inflammation of thepapillary and reticular dermis

Higher magnification of left submammary crease lesion withdeep dermal granulomatous inflammation consisting ofmultinucleated giant cells, epithelioid histiocytes, and alymphocytic infiltrate

Low-power image of an abdominal skin biopsy illustratingdiffuse granulomatous inflammation involving thepapillary and reticular dermis

Labial biopsy showing diffuse inflammation of thepapillary dermis consisting of multinucleated giantcells, epithelioid histiocytes, and a lymphocyticinfiltrate

CROHNS DISEASE MCD Lymphoplasmacytic predominantly diffuse infiltrate in the mucosa pattern commonly seen in the dermis and subcutis. Acute inflammatory cells neutrophils are rarely a may be focally present in feature the crypt lumens (crypt abscess) or in the crypt The presence of granulomas epithelium (cryptitis) Langerhans giant cells are Closely arranged frequently seen along with epithelioid histiocytes and an collections of histiocytes accompanying with no foreign bodygiant lymphoplasmacytic infiltrate cells present.

CROHNS DISEASE MCD Not seen Perivascular granulomatous Skip lesions, neural inflammation and hypertrophy, Paneth cell eosinophils metaplasia, and pyloric gland metaplasia. ulceration of MCD lesions can occur. Lesions of Crohn Metastatic Crohn disease directly disease lesions by involving the skin are definition occur at sites located at sites discontiguous from the continuous with the gastrointestinal tract gastrointestinal tract.

underlying etiology of MCD - unknown. It has been suggested that antigens or immune complexes stemming from the gastrointestinal tract in primary Crohn disease travel through the circulatory system and deposit in the skin, creating perivascular granulomatous features seen on microscopic examination of MCD lesions. Autoimmune cross-reactivity also been suggested The granulomatous inflammation has also been attributed to a type IV hypersensitivity reaction wherein T cells cross-react with skin antigens, resulting in an inflammatory response similar to that seen in the gastrointestinal tract of Crohn disease

Cutaneous sarcoidosis, Erythema nodosum, Pyoderma gangrenosum, Hidradenitis suppurativa, Mycobacterial disease, and Foreign body reaction

Cutaneous sarcoidosis : consists of granulomas located in the skin with minimal lymphocytic infiltrate also termed naked granulomas. This granulomatous inflammation is different from that of MCD, which usually consists of a prominent lymphoplasmacytic infiltrate. Epidermal ulceration is relatively uncommon in cutaneous sarcoidosis.

Erythema nodosum : one of the most common cutaneous manifestations of Crohn disease presents microscopically with granulomatous inflammation involving the septae of the subcutis (ie, septal panniculitis) with a mixed inflammatory infiltrate including neutrophils in the acute phase.

Superficial granulomatous pyoderma : the presence of focal neutrophilic abscesses and pseudoepitheliomatous hyperplasia

Hidradenitis suppurativa : involves suppurative granulomatous inflammation with folliculitis and abscess formation. Although it may involve anatomic sites common to MCD such as the anogenital region with granulomatous lesions, its follicular involvement with keratin plugging and ruptured follicles make its microscopic diagnosis distinct.

For all granulomatous lesions, appropriate ancillary stains for infectious etiology (Gram stain, periodic acid Schiff/Gomori methenamine silver, acid-fast bacilli) & cultures to rule out mycobacterial disease, fungal infection, and other microbial agents Polarizing microscopy may also be utilized to rule out granulomatous lesions of the skin caused by foreign material.

A gastrointestinal workup for inflammatory bowel disease should be considered when MCD is diagnosed without a previous history of Crohn disease

Numerous agents have been used in the literature with varying success, including oral and topical steroids, oral antibiotics, azathioprine, sulfasalazine, 6-mercaptopurine, metronidazole,and infliximab Infliximab appears to show promising results with respect to severe and refractory cases of MCD.

Hyperbaric oxygen has also been utilized in the treatment of MCD Patients appear to have also responded to surgical debridement, especially in cases refractory to medical therapy. Although considered rare, cases involving spontaneous regression of MCD lesions have also been reported

Metastatic Crohn disease is a rare cutaneous manifestation of Crohn disease. It is defined as the presence of noncaseating granulomatous lesions of the skin at sites anatomically separate from the gastrointestinal tract. Adults and children tend to have different clinical presentations. The differential diagnosis of MCD includes infectious and noninfectious entities presenting as granulomatous skin lesions. A variety of therapeutic modalities have been described in the literature, with infliximab and surgery showing the most promise in terms of severe, refractory cases.