ISSN 2398-2950      

Skin: panniculitis due to rapidly growing mycobacteria


Synonym(s): RGM, Non-tuberculous mycobacteria, NTM opportunistic


  • In both humans and animals, rapidly-growing mycobacteria (RGM) are strongly linked with localized infections of immunocompetent hosts. They are distributed ubiquitously in nature and can be isolated from soil, dirt and water.
  • RGM include the M. fortuitum group (including M. fortuitumM. peregrinum and the 3rd biovariant complex), the M.chelonae/abscessus group (including M. chelonae and M. abscessus), the M. smegmatis group (including M. smegmatis sensu strictoM. goodii and M. wolinskyi) and a variety of other species including M. phlei and M. thermoresistibile.
  • RGM produce three different syndromes in cats and dogs:
    • Mycobacterial panniculitis.
    • Pyogranulomatous pneumonia.
    • Disseminated systemic disease.
  • Cause: rapidly-growing mycobacteria (RGM) enter skin typically following penetrating injury especially when wound is contaminated by dirt or soil. Organisms gain entry to the lung through aspiration of material, likely with concurrent lipid material (eg paraffin oil given to constipated cats).
  • Signs: circumscribed plaque or nodule apparent at site of injury. The infection then spreads circumferentially into contiguous subcutaneous tissues. Draining sinus tracts develop subsequently.
  • Diagnosis: cytology and histology provide a presumptive diagnosis, definitive diagnosis via culture and/or PCR of fresh biopsy material dissected from skin.
  • Treatment: antimicrobial therapy and surgical resection of affected tissue.
  • Prognosis: good with appropriate therapy.



  • Early in their clinical course, infections can resemble cat fight abscesses Abscess, but without the characteristic fetid odour and turbid pus. Instead, a circumscribed plaque or nodule is apparent at the site of injury. Later, there is progressive thickening of the nearby subcutis to which overlying skin becomes adherent. Affected areas become denuded of hair and numerous punctuate fistulae appear, discharging a watery exudate. Fistulae are intermingled with focal purple depressions, which correspond to thinning of the epidermis over accumulations of pus. The lesion gradually increases in area and depth, and may eventually involve the entire ventral abdomen, adjacent flanks or limbs. If cats are presented promptly for veterinary attention and the lesion confused with an anaerobic cat bite abscess, surgical drainage and administration of a synthetic penicillin is typically followed by wound breakdown and development of a non-healing suppurating tract surrounded by indurated granulation tissue.
  • Some affected cats with severe infections develop systemic signs:
    • Depression, pyrexia, inappetence, loss of weight and reluctance to move.
  • Occasional cats develop the hypercalcemia Hypercalcemia: overview of granulomatous disease, although this is rarely if ever symptomatic. Surprisingly, other cats remain comparatively well despite extensive disease. Usually the problem remains localized to the skin and subcutis. Although adjacent structures such as the abdominal wall can be affected eventually, spread to internal organs or lymph nodes is very unusual.
  • Mycobacterial panniculitis: chronic infection of the subcutis and skin with RGM. Preference of RGM for fat is a key factor in the pathogenesis of these infections and results in a tendency for disease to occur in obese cats and in tissues rich in lipid, such as the subcutaneous panniculus and especially the inguinal fat pad of cats. In Australia the M. smegmatis group accounts for the majority of feline cases. In the USA, M. fortuitum and M. chelonae are more prevalent. 
  • Pyogranulomatous pneumonia: coughing, dyspnea, fever, malaise and often loss of weight due to poor appetite.

Predisposing factors


  • Outdoor access.
  • Obesity Obesity - especially where there is abundant subcutaneous fat.


  • Penetrating injury.


  • The incubation period has not been clearly determined. Disease progression is slow, but progressive and insidious. Spontaneous remission almost never occurs, ie cases tend to progress without veterinary interventions. To cure the patient, intervention is required.


This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login


This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login


This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login


This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Horne K S & Kunkle G A (2009) Clinical outcome of cutaneous rapidly growing mycobacterial infections in cats in the south-eastern United States: a review of 10 cases (1996-2006). J Feline Med Surg 11 (8), 627-632 PubMed.
  • Jassies-van der Lee A, Houwers D J, Meertens N et al (2009) Localised pyogranulomatous dermatitis due to Mycobacterium abscessus in a cat: a case report. Vet J 179 (2), 304-306 PubMed.
  • Malik R, Shaw S E, Griffin C et al (2004) Infections of the subcutis and skin of dogs caused by rapidly growing mycobacteria. JSAP 45 (10), 485-494 PubMed.
  • Brown-Elliot B A, Wallace R J Jr. (2002) Clinical and taxonomic status of pathogenic nonpigmented or late-pigmenting rapidly growing mycobacteria. Clin Microbiol Rev 15 (4), 716-746 PubMed.
  • Brown-Elliot B A, Wallace R J Jr., Crist C J et al (2002) Comparison of in vitro activities of gatifloxacin and ciprofloxacin against four taxa of rapidly growing mycobacteria. Antimicrob Agents Chemo 46 (10), 3283-3285 PubMed
  • Jang S S, Hirsh D C (2002) Rapidly growing members of the genus Mycobacterium affecting dogs and cats. JAAHA 38 (3), 217-220 PubMed.
  • Hunt G B, Tisdall P L, Liptak J M et al (2001) Skin-fold advancement flaps for closing large proximal limb and trunk defects in dogs and cats. Vet Surg 30 (5), 440-448 PubMed
  • Malik R, Wigney D I, Dawson D et al (2000) Infection of the subcutis and skin of cats with rapidly growing mycobacteria: a review of microbiological and clinical findings. J Fel Med Surg (1), 35-48 PubMed
  • Irwin P J, Whithear K, Lavelle R B et al (2000) Acute bronchopneumonia associated with Mycobacterium fortuitum in a dog. Aust Vet J 78 (4), 254-257 PubMed
  • Melendez L D, Twedt D C, Wright M (2000) Suspected doxycycline-induced esophagitis with esophageal stricture formation in three cats. Fel Pract 28 (2), 10-12 VetMedResource
  • Foster S F, Martin P, Davis W et al (1999) Chronic pneumonia caused by Mycobacterium thermoresistible in a cat. Journal of Small Animal Practice 40 (9), 433-438 Wiley Online Library
  • Grooters A M, Couto C G, Andrews J M et al (1995) Systemic Mycobacterium smegmatis infection in a dog. J Am Vet Med Assoc 206 (2), 200-202 PubMed.  
  • Hunt G B (1995) Skin-fold advancement flaps for closing large sternal and inguinal wounds in cats and dogs. Vet Surg 24 (2), 172-175 PubMed.
  • Hoffner S, Klintz L, Olsson-Liljequist B et al (1994) Evaluation of Etest for rapid susceptibility testing of Mycobacterium chelonae and M fortuitum. J Clin Microbiol 32 (8), 1846-1849 PubMed
  • Lewis D T, Hodgin E C, Foil C S et al (1994) Experimental reproduction of feline Mycobacterium fortuitum panniculitis. Vet Dermatol (4), 189-195 VetMedResource
  • Malik R, Hunt G B, Goldsmid S E et al (1994) Diagnosis and treatment of pyogranulomatous panniculitis due to Mycobacterium smegmatis in cats. J Sm Anim Pract 35 (10), 524-530 VetMedResource
  • Michaud A J (1994) The use of clofazimine as treatment for Mycobacterium fortuitum in a cat. Fel Pract 22 (3), 7-9 VetMedResource
  • Wylie K B, Lewis D D, Pechman R D et al (1993) Hypertrophic osteopathy associated with Mycobacterium fortuitum pneumonia in a dog. J Am Vet Med Assoc 202 (12), 1986-1988 PubMed.
  • Plaus W J, Hermann G (1991) The surgical management of superficial infections caused by atypical mycobacteria. Surgery 110 (1), 99-103 PubMed.
  • Thomson J R, Mollison N, Matthews K P (1988) An investigation of mastitis due to S agalactiae, S uberis and M smegmatis in a dairy herd. Vet Rec 122 (12), 271-274 PubMed
  • Turnwald G H, Pechman R D, Turk J R et al (1988) Survival of a dog with pneumonia caused by Mycobacterium fortuitum. J Am Vet Med Assoc 192 (1), 64-66 PubMed.  
  • Gross T L, Connelly M R (1983) Nontuberculous mycobacterial skin infections in two dogs. Vet Pathol 20 (1), 117-119 PubMed
  • Kunkle G A, Gulbas N K, Fakok V et al (1983) Rapidly growing mycobacteria as a cause of cutaneous granulomas: report of five cases. J Am Anim Hosp Assoc 19 (4), 513-521 VetMedResource

Other sources of information

  • Malik R, Martin P, Wigney D & Foster S (2006) Infections caused by rapidly growing mycobacteria. In: Infectious diseases of the Dog & Cat. 3rd edn. Greene C E (ed), W B Saunders CO., Philadelphia, PA. pp 480-488.
  • Wilkinson G T, Mason K V (1991) Chapter 19: Clinical Aspects of Mycobacterial Infections of the Skin. August, JR, ed. In: Consultations in Feline Internal Medicine.WB Saunders, Philadelphia, pp 129-136.

Can’t find what you’re looking for?

We have an ever growing content library on Vetlexicon so if you ever find we haven't covered something that you need please fill in the form below and let us know!


To show you are not a Bot please can you enter the number showing adjacent to this field

 Security code