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Panniculitis 747

Panniculitis
VetBooks.ir Initial Database Diseases and Disorders

with accompanying constitutional signs such
BASIC INFORMATION
as lethargy, anorexia, and pyrexia • Cytologic examination; to identify infectious
Definition organisms, if present
Inflammation of the subcutaneous adipose tissue PHYSICAL EXAM FINDINGS ○ Gram-positive, branching, filamentous
(i.e., panniculitis) is different from cellulitis, • Lesions typically involve the trunk and may organisms: Actinomyces sp (nonacid-fast);
which is an acute, diffuse, and suppurative be single or multifocal. Nocardia sp (partially acid-fast)
inflammation of loose connective tissue, • Subcutaneous nodules/swellings may become ○ Diff-Quik: fungi possible (systemic
particularly the deep subcutaneous tissues, and cystic-like and painful, especially before mycoses)
sometimes muscle, most commonly resulting rupturing or developing draining tracts. ○ Acid-fast bacilli: atypical mycobacteria,
from infection of a wound, ulcer, or other skin • Skin superficial to nodules may be atrophic. feline Mycobacterium lepraemurium
lesion. Panniculitis is not a definitive diagnosis • Panniculitis and subsequent fat necrosis ○ Organisms may be seen within foamy
but rather an inflammatory condition with are characterized by an oily yellow-brown macrophages.
numerous causes. to blood-tinged discharge. • Full-thickness skin (epidermis plus subcu-
• Lesions often heal with crusting, pigmenta- taneous fat) biopsy; panniculus must be
Epidemiology tion, and scarring. included; consider double-punch technique.
SPECIES, AGE, SEX Histopathologic analysis:
Uncommon in dogs and cats Etiology and Pathophysiology ○ Qualify cellular infiltrate (neutrophilic, eosin-
• Panniculitis is caused by inflammation and/ ophilic, granulomatous, pyogranulomatous).
GENETICS, BREED PREDISPOSITION or infection of the panniculus (subcutaneous ○ Identify infectious organisms (special
Sterile nodular panniculitis: dachshunds, collies, fat) with subsequent oxidative damage to the stains).
and miniature poodles lipocytes. ○ Severity of lesions (necrosis, fibrosis,
• Result: release of free lipids into subcutis, vasculitis)
RISK FACTORS resulting in fat saponification with further
• Outdoor pets (penetrating foreign body, bite worsening of inflammation and granuloma- Advanced or Confirmatory Testing
wound): infectious panniculitis tous reactions. • Clinicians should aseptically submit part
• Obesity: mycobacteriosis of a biopsy specimen for tissue maceration
• Immunocompromised cat (e.g., feline leuke- DIAGNOSIS and culture and possibly polymerase chain
mia virus [FeLV], feline immunodeficiency reaction (PCR) (tissue or swabs).
virus [FIV]) or dog (e.g., iatrogenic hyperad- Diagnostic Overview ○ Consult laboratory for suspected
renocorticism): greater risk of dissemination Panniculitis has several causes but is initially organism(s), preference of culture media,
of infectious organisms suspected based on physical finding of subcu- incubation times, and necessary precau-
• Unbalanced diets low in antioxidants (e.g., taneous swellings/nodules (pseudotumor) that tions for lab personnel.
low levels of vitamin E) may or may not be painful or have developed ○ Bacterial culture and sensitivity testing
• Recurrent pancreatitis: panniculitis and draining tracts. Biopsies for histopathologic ○ Rapid-growing, atypical mycobacterial
steatitis (inflammation of body fat) evaluation and culture (bacterial and fungal) culture
• Pancreatitis or pancreatic carcinomas: are required for diagnosis. Idiopathic sterile ○ Fungal culture (not usually for sys-
mineralizing fat necrosis/panniculitis nodular panniculitis is diagnosed with 1) sup- temic mycoses; other tests are safer to
portive histopathologic findings, 2) exclusion of personnel)
CONTAGION AND ZOONOSIS an infectious cause, and 3) failure to identify ○ PCR for mycoses and leishmania
• Dermatophytic granulomatous panniculitis: other known causes of panniculitis. • Serologic evaluation: systemic mycoses
Microsporum canis and Trichophyton menta- • Direct fluorescent antibody testing for
grophytes are potentially contagious to other Differential Diagnosis Sporothrix antigen
animals and are zoonotic. Inflammatory: • Abdominal ultrasound: pancreatic diseases
• Sporotrichosis: risk of cat-to-human trans- • Infectious: abscess, bacterial/botryomycosis, may be a contributing factor (rare).
mission is extremely high; dog-to-human actinomycosis, nocardiosis, atypical myco-
transmission has not been reported. bacteriosis, feline leprosy, Bartonella spp TREATMENT
• Blastomycosis, coccidioidomycosis, histo- (bacillary angiomatosis), dermatophytic
plasmosis: risk of zoonosis by aerosol from pseudomycetoma, subcutaneous and systemic Treatment Overview
culture plates; in-house culture is always mycoses, oomycoses, leishmaniasis Because panniculitis has a variety of causes,
contraindicated. • Noninfectious: trauma (including surgical selection and duration of treatment depend
sites), foreign body (e.g., suture), ruptured on identification of the specific cause.
GEOGRAPHY AND SEASONALITY follicular cyst, insect bite, vitamin E defi-
Sporotrichosis has a worldwide distribution but ciency, pancreatitis/pancreatic carcinoma, Acute General Treatment
may occur in regional outbreaks (e.g., Brazil). injection-site reaction (e.g., repository • Surgical excision of solitary lesions for
glucocorticoids, rabies vaccination), sterile diagnosis and possibly cure
ASSOCIATED DISORDERS vasculitis, lupus erythematosus, drug • Appropriate antifungal, antibacterial, anti-
Interscapular panniculitis may be a precursor reaction, feline cutaneous lymphocytosis, mycobacterial, or antiprotozoal treatment if
of injection-site sarcoma in cats. calcinosis cutis, idiopathy (sterile nodular indicated
panniculitis)
Clinical Presentation Neoplastic: Chronic Treatment
HISTORY, CHIEF COMPLAINT • Benign: follicular tumors, lipoma Sterile panniculitis (e.g., rabies vaccine–induced,
Acute to chronic onset of single or multiple sub- • Malignant: mast cell tumor, cutaneous lym- systemic lupus erythematosus, vasculitis, sterile
cutaneous nodules or draining tracts, potentially phoma, malignant histiocytosis, liposarcoma nodular):

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