NAVLE Integumentary

Feline Diseases of Pads Study Guide

📅 March 28, 2026 ⏱ 25 min read
Feline paw pad diseases (pododermatitis) represent a distinct group of dermatologic conditions that are frequently encountered on the NAVLE. Unlike canine pododermatitis, feline paw pad diseases have unique etiologies and presentations.

Overview and Clinical Importance

Feline paw pad diseases (pododermatitis) represent a distinct group of dermatologic conditions that are frequently encountered on the NAVLE. Unlike canine pododermatitis, feline paw pad diseases have unique etiologies and presentations. The term pododermatitis describes inflammation affecting the paws, including the paw pads, interdigital spaces, and nail folds (paronychia).

The most commonly tested feline paw pad conditions on the NAVLE include: Plasma Cell Pododermatitis (Pillow Foot), Pemphigus Foliaceus, Eosinophilic Granuloma Complex, Feline Lung-Digit Syndrome, and Squamous Cell Carcinoma. Recognition of clinical patterns and understanding of pathophysiology are essential for diagnosis and treatment.

Feature Description
Pads Affected Central metacarpal and metatarsal pads most commonly affected; usually multiple feet involved; rarely single foot
Classic Appearance Soft, spongy, doughy swelling with characteristic "mushy" texture; pads balloon out like pillows
Surface Changes White silvery striae (striations) crossing the pad surface; fine scaling/exfoliation; crosshatched appearance
Color Changes Depigmentation; erythema; violaceous (purplish) discoloration in light-colored pads
Progressive Disease Ulceration (20-35% of cases); bleeding; granulation tissue formation; secondary infection
Pain/Lameness Greater than 70% of cats present with lameness as primary complaint, especially with ulceration; some cats surprisingly asymptomatic

Feline Paw Pad Anatomy Review

Cats have six paw pads per front foot and five per rear foot. The major pads include the central metacarpal/metatarsal pad (largest pad) and the digital pads associated with each digit. Key anatomic features:

  • Epidermis: Thick, keratinized epithelium providing protection and traction
  • Dermis: Contains blood vessels, nerves, and eccrine sweat glands (only location in cats)
  • Subcutis: Fatty cushion providing shock absorption
  • Digital arteries: Terminal branches make pads susceptible to embolic disease
Drug Dosage Notes
Doxycycline (First-line) 10 mg/kg PO q24h Immunomodulatory effects; 35% complete remission, 53% partial improvement; continue until resolution (up to 10 weeks); give with water bolus to prevent esophagitis
Prednisolone 2.2-4.4 mg/kg PO q24h Immunosuppressive; taper after remission achieved; may use alone or with doxycycline
Cyclosporine 7 mg/kg PO q24h Alternative immunomodulatory option; continue until remission then taper
Dexamethasone 0.1-0.2 mg/kg PO q24h Sometimes more effective than prednisolone in cats; taper after improvement
Surgical Excision N/A Reserved for refractory cases; wide excision of affected pads can be curative

Plasma Cell Pododermatitis (Pillow Foot)

Definition and Etiology

Plasma cell pododermatitis (PCP), commonly called pillow foot, is an uncommon immune-mediated condition characterized by plasma cell infiltration of the footpads. The exact etiology remains unknown, but evidence supports an immune-mediated process based on consistent hypergammaglobulinemia, marked tissue plasmacytosis, and response to immunomodulatory therapy.

Associated Conditions

  • FIV positivity: 44-63% of affected cats are FIV-positive
  • FeLV: Less commonly associated
  • Concurrent conditions: Plasmacytic stomatitis, immune-mediated glomerulonephritis, renal amyloidosis
  • Seasonal relapses: May suggest environmental allergen involvement
High-YieldOn the NAVLE, always recommend FIV/FeLV testing for any cat presenting with plasma cell pododermatitis. Approximately 50% of affected cats are FIV-positive!

Signalment

  • No age, breed, or sex predilection (can affect cats from 6 months to 12 years)
  • Some studies suggest male castrated domestic shorthair cats may be overrepresented

Clinical Signs

Diagnosis

Clinical Diagnosis

The classic clinical appearance of bilateral soft, spongy paw pad swelling with striae is often pathognomonic. Multiple feet involvement strongly supports the diagnosis.

Fine Needle Aspirate (FNA)

FNA of affected pads reveals large numbers of plasma cells (ovoid cells with eccentric nucleus and pale perinuclear area corresponding to Golgi apparatus). Mixed inflammatory cells with neutrophils may also be present.

Histopathology (Definitive)

  • Severe, diffuse dermal and perivascular plasma cell infiltration
  • Mott cells: Plasma cells containing Russell bodies (spherical cytoplasmic inclusion bodies of immunoglobulin)
  • Extension into hypodermal adipose tissue
  • Epidermal changes: acanthosis, erosion, ulceration

Laboratory Findings

  • Hypergammaglobulinemia: Polyclonal gammopathy on serum protein electrophoresis
  • Lymphocytosis or lymphopenia
  • Thrombocytopenia
  • FIV/FeLV testing: Always recommended

Treatment

Prognosis

  • Generally good: Most cats respond to treatment within 1-2 months
  • Spontaneous remission: May occur in some mild cases
  • Relapses possible: Some cats require lifelong therapy
  • Poor prognosis: If concurrent glomerulonephritis or renal amyloidosis present
NAVLE TipWhen you see a cat with soft, spongy, swollen pads affecting multiple feet with silvery striae, think Plasma Cell Pododermatitis first! Remember the mnemonic: "PILLOW = Plasma cells, Immune-mediated, Lymphocytosis, Low platelets, Often FIV+, Watch for glomerulonephritis"
Drug Dosage Notes
Prednisolone (First-line) 2.2-4.4 mg/kg PO q24h Most cats achieve remission with glucocorticoid monotherapy; taper after 2-4 weeks
Dexamethasone 0.1-0.2 mg/kg PO q24h May be more effective than prednisolone in some cats
Chlorambucil 2 mg PO q48h Add if glucocorticoids alone ineffective; steroid-sparing agent
Cyclosporine 7 mg/kg PO q24h Alternative immunosuppressive option
Mycophenolate mofetil 10 mg/kg PO q12h Steroid-sparing agent; monitor for GI effects

Pemphigus Foliaceus

Definition and Pathophysiology

Pemphigus foliaceus (PF) is the most common autoimmune skin disease in cats, accounting for approximately 1% of dermatology cases. It results from autoantibodies targeting desmosomes (intercellular adhesion molecules) between keratinocytes, causing acantholysis (loss of intercellular cohesion) in the superficial epidermis leading to subcorneal pustule formation.

Signalment

  • No age, breed, or sex predisposition
  • Can occur in cats less than 1 year to greater than 16 years
  • Domestic shorthair most commonly affected (due to population prevalence)

Clinical Signs

Lesions typically begin on the face and progress to other sites. Classic distribution includes face, pinnae, and feet/footpads.

Paw Pad Involvement

  • Paronychia: Severe nail fold inflammation with caseous (cheesy) discharge - unique feature in cats
  • Footpad hyperkeratosis: Thickened, scaly pads
  • Crusting and erosions: On and around paw pads
  • Onychodystrophy: Nail abnormalities with nail fold lesions
  • Distribution: Usually bilateral and symmetrical, affecting all four feet

Other Body Site Involvement

  • Face: nose, muzzle, periocular area - pustules and crusts
  • Pinnae: inner surface with crusting
  • Periareolar crusting: Around nipples (characteristic feline finding)
  • Pruritus present in 65-80% of cats

Systemic Signs

More common in cats than dogs: fever, lethargy, anorexia, lymphadenopathy

Diagnosis

Cytology

Sample intact pustules or material from under crusts. Look for acantholytic cells: Rounded keratinocytes with dark cytoplasm and central nuclei resembling "fried eggs" surrounded by nondegenerate neutrophils.

Histopathology (Definitive)

  • Subcorneal or intragranular pustules
  • Acantholytic keratinocytes within pustules
  • Neutrophils (and sometimes eosinophils) in pustules

Treatment

Prognosis

Good: Approximately 90% of cats achieve remission. Most require long-term or lifelong immunosuppressive therapy. Remission typically occurs within 1-2 months. Relapses are common when medication discontinued.

High-YieldOn cytology, look for "fried egg" acantholytic cells surrounded by neutrophils. Pemphigus foliaceus does NOT affect mucosal surfaces (mouth, eyes), unlike deeper forms of pemphigus. Use PREDNISOLONE, not prednisone, in cats due to better bioavailability!
Feature Plasma Cell Pododermatitis Pemphigus Foliaceus Lung-Digit Syndrome Eosinophilic Granuloma
Feet Affected Multiple (usually all 4) Multiple (bilateral symmetric) Single or multiple Usually single foot
Pad Appearance Soft, spongy, pillowy with striae Crusts, hyperkeratosis, paronychia Firm swelling, nail deviation/loss Nodular, raised lesions
Other Body Sites Nose bridge swelling (rare) Face, pinnae, nipples Lung mass (primary tumor) Thighs, lip, oral cavity
Key Diagnostic Finding Plasma cells on FNA; hyperglobulinemia Acantholytic cells; subcorneal pustules P3 osteolysis on radiograph; lung mass Eosinophils on cytology
First-Line Treatment Doxycycline 10 mg/kg Prednisolone 2-4 mg/kg Palliative (grave prognosis) Allergy workup + steroids
Prognosis Good (most respond) Good (90% remission) Grave (mean 58 days) Good if allergy controlled

Feline Lung-Digit Syndrome

Definition and Pathophysiology

Feline lung-digit syndrome (FLDS) describes the unusual metastatic pattern of primary pulmonary tumors (most commonly bronchogenic adenocarcinoma) to the digits. Tumor cells embolize through pulmonary veins, pass through the heart into systemic circulation, and lodge in the distal digital arteries. The digits are preferred sites due to terminal arterial blood supply.

Critical Point: Up to 88% of carcinomas in feline digits are metastatic from a primary pulmonary neoplasm. Approximately 1 in 6 amputated feline digits contain metastatic disease.

Signalment

  • Age: Older cats (mean 12 years, range 2-20 years)
  • No consistent breed or sex predilection

Clinical Signs

Digital Lesions

  • Swelling: Firm swelling of distal digit(s)
  • Ulceration: Digital skin or nail bed ulceration
  • Purulent discharge: Serosanguineous or purulent discharge from nail bed
  • Nail changes: Fixed exsheathment, deviation, or loss of nail
  • Lameness: Often the primary presenting complaint
  • Distribution: Weight-bearing digits most commonly affected; multiple digits and multiple paws; dewclaws never affected

Respiratory Signs

CRITICAL: Most cats with FLDS do NOT present with respiratory signs! Only 25-50% of cats with pulmonary neoplasia show respiratory signs. Digital lesions often precede respiratory signs by weeks to months.

Systemic Signs

Lethargy, depression, anorexia, weight loss, diarrhea, vomiting

Diagnosis

Digital Radiographs

Classic findings: Osteolysis of P3 (distal phalanx), often extending to P2 with trans-articular invasion. Periosteal proliferation may also be present. This radiographic pattern should immediately raise suspicion for FLDS.

Thoracic Radiographs

MANDATORY before any digital surgery. Usually reveals pulmonary mass(es) - often solitary, nodular, located in caudal lung lobes. May see pleural effusion, enlarged tracheobronchial lymph nodes.

Histopathology

Biopsy of digit reveals metastatic adenocarcinoma with characteristic features: acinar/tubular structures, ciliated columnar epithelium, goblet cells, PAS-positive material. TTF-1 (thyroid transcription factor-1) immunohistochemistry positive confirms pulmonary origin.

Treatment and Prognosis

Prognosis is GRAVE. Mean survival time is 58 days after diagnosis; median 67 days. No effective treatment has been demonstrated.

  • Digit amputation: Not curative; further metastases rapidly develop
  • Lung lobectomy: Only if solitary mass with no visible metastases; median survival 698 days for well-differentiated tumors, 75 days for poorly-differentiated
  • Palliative care: NSAIDs (piroxicam 0.3 mg/kg PO q24h), buprenorphine, tramadol for pain management
NAVLE TipCRITICAL EXAM POINT: Any older cat presenting with digital swelling and lameness needs THORACIC RADIOGRAPHS before any digital surgery! Approximately 90% of digital carcinomas in cats are metastatic from the lung. Remember: "FLDS = Find Lung tumor, Save unnecessary Surgery." The classic presentation is an elderly cat with painfully swollen toe(s) and NO respiratory signs.

Eosinophilic Granuloma Complex (Paw Pad Involvement)

Definition and Pathophysiology

Eosinophilic granuloma (EG) is one of three components of the Feline Eosinophilic Granuloma Complex (FEGC), along with eosinophilic plaque and indolent (rodent) ulcer. EG represents a cutaneous reaction pattern, not a final diagnosis. The underlying cause is usually hypersensitivity to fleas, environmental allergens, or food allergens. Eosinophils release inflammatory chemicals causing collagen damage.

Clinical Signs - Footpad Involvement

  • Nodular proliferations: Raised, firm nodules on footpads
  • Ulceration: Nodules often ulcerate from weight-bearing pressure
  • Usually single foot: Unlike plasma cell pododermatitis which affects multiple feet
  • Lameness: Due to pad lesions
  • Pruritus or pain: Variable

Classic EG Lesions Elsewhere

Linear lesions on caudal thighs; swollen chin/lower lip; oral lesions on tongue or palate; raised yellowish-pink plaques

Diagnosis

Cytology

FNA or impression smears show predominantly eosinophilic infiltrate with mixed inflammatory cells

Histopathology

  • Superficial to deep perivascular dermatitis with eosinophilia
  • Collagen degeneration (collagenolysis)
  • Eosinophilic microvesicles and microabscesses

Treatment

  • Address underlying cause: Flea control, food elimination diet, allergy workup
  • Glucocorticoids: Prednisolone 1-2 mg/kg PO q24h until remission, then taper
  • Cyclosporine: 7 mg/kg PO q24h for refractory cases
  • Spontaneous remission: May occur in some cases
High-YieldEosinophilic granuloma on footpads usually affects only ONE foot, whereas plasma cell pododermatitis affects MULTIPLE feet. Always rule out underlying allergies. Remember: EG is a reaction pattern, not a diagnosis - find the underlying cause!

Differential Diagnosis Comparison

Mnemonic: "PADS" for Feline Paw Pad Diseases

  • P = Plasma cell pododermatitis (Pillow foot - soft, spongy, multiple feet)
  • A = Autoimmune pemphigus (Acantholytic cells, paronychia, face involvement)
  • D = Digital metastasis (Deadly lung-digit syndrome, older cats, thoracic rads mandatory)
  • S = Sensitivity/allergy (Eosinophilic granuloma, usually single foot)

Quick Recall: Number of Feet Affected

  • Multiple feet = Plasma cell pododermatitis or Pemphigus foliaceus
  • Single foot = Eosinophilic granuloma, foreign body, bacterial/fungal granuloma, neoplasia

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