Degenerative Mucinotic Mural Folliculitis (DMMF) is a rare, poorly understood syndrome in cats, defined as an inflammatory reaction pattern. It is characterized by inflammation of the hair follicle, atrophy degeneration and mucin production. The inflammatory reaction, takes place on the follicle wall, primarily affecting the external sheath of the hair above the follicular isthmus. However it can also affect the infundibulum or the bulbar portion of the hair follicle.
Literature (incl. case studies) regarding feline DMMF is sparse. It can be briefly summarized as follows: All described cases are in middle aged to older cats, the majority of which are male, with no information on breed predisposition. The most characteristic features are: Alopecia of the face, head and neck and in a later stage affecting the body and limbs. Pruritus, if present, is mild to very intense. The diagnosis is confirmed by biopsy and subsequent histopathological examination.
Mila is an approximately 1,4 years old spayed female cat. She used to be a stray cat, until a lady, regularly
feeding her, noted dramatic changes to the cat’s fur. The lady temporarily adopted the cat and took her to several veterinarians. The lady provided shelter to about 20 other cats. According to the owner all cats were treated monthly with Broadline (Merial).
Picture 1.1, 1.2 Mila before the onset of her skin problem
First signs were: hypotrichosis of the face (pic. 2.1) and subsequent minor hypotrichosis of the distal parts of the limbs (pic. 2.2)
The cat’s skin condition gradually worsened. She showed progressive hypotrichosis, and alopecia, with severe pruritus. She was seen by a veterinarian and treated with Synulox (Zoetis) orally for 20 days, which reduced the inflammatory signs. Later she was seen by another veterinarian and underwent the following treatments (in a period of 3-4 months):
Pulse therapy (7 days of medication, 7 day break etc.) with oral itraconazole 5mg/kg q24h. Without good response.
Purina Pro Plan veterinary diets HA Hypoallergenic, for two months.
Ivermectin 0.3mg/kg q24h orally for 10 days.
According to the owner, the cat’s skin condition worsened. Described signs included: Pruritus, hypotrichosis, alopecia, skin hyperpigmentation and presence of scales and crusts.
The cat was admitted to our hospital for a second opinion. As as side note: Once admitted to our clinic, the lady signed the cat over to a local charity Redom.
The cat presented with the following signs:
- Symmetrical alopecia of the face and head. The skin had a thickened and swollen appearance.
- Severe pruritus (9/10 – 10/10)
- Hypotrichosis and alopecia of the entire body.
- Hyperpigmentation, scales and crusts covering the dorsum.
- Very passive and apathetic.
- According to the owner the animal is not feeling well, has an increased water intake and softer stools, with more frequent defecation than usual.
Differential diagnoses (several)
Feline atopic syndrome (allergies)
Feline sebaceous adenitis
Degenerative mucinous mural folliculitis
FIV / FeLV
Thymoma-associated exfoliative dermatitis in cats
The cat was hospitalized for further diagnostics and treatment was started, while waiting for the results of histopathology.
Results of clincial exam and diagnostic tests:
Skin scrape, hair plaque, tape strip: All negative for Demodex and Notoedres mites.
Tape strip cytology: Epithelial cells, but no neutrophils or Malassezia.
The ears have brown ear wax; Cytology – only epithelial cells, no Malassezia and no Otodectes cynotis.
CBC: WBC HH 58.24×109/L(5-19,5); NEU 25×109/L(2-12,5); LYM 16×109/ L; MONO 7,21 x109/L (0,15-1,7); EOS 8,58×109/L (0,1-0,79); BASO 0,13 x 109/L (0-0,1).
Blood Biochemistry: All parameters within normal range.
TT4= 18 nmol/l (10-80).
Urine: pH 7; PRO 30 mg/dl; GLU, KETO, UBG, BIL and BLOOD negative. No sediment.
Abdominal Ultrasound: Except for slightly enlarged inguinal lymph nodes, the other abdominal organs were unremarkable.
Chest radiographs: Bronchial pattern, possible cause could be lung worms. (Picture 4)
Fecal flotation: Negative
PCR (antigen) Assays: FCoV, FIV, FeLV, Toxoplasma gondii and Giardia ALL negative.
Skin biopsy: Histopathology results below.
Lymph node biopsy: Histopathology results below.
Picture 5 (5.1-5.4): The cat is licking and biting her legs and tail, as well as scratching her neck.
Intravenous fluids: Ringer’s lactate solution 10 ml/h for 5 days. Antibiotics: Ceftriaxone 30 mg/kg IV q12h and Enrofloxacin 5 mg/kg SC q24h for 14days each. Anti-parasitic: Fenbendazole 50 mg/kg PO q24h for 5 days. Antihistamine: Diphenhydramine 1,5 mg/kg SC q24h for 2 weeks. Continuation of Purina Pro Plan veterinary diets HA Hypoallergenic and supplementing this with 4 drops YuMEGA cat (omega-3, -6, -9 fatty acids) once daily. A single application of dexamethasone 0,25 mg/kg SC, resulted in a major reduction of the pruritus!
The CBC was repeated the next day, but did not show significant changes. However the CBC 48h after hospitalization did: WBC HH 44.8×109/L(5-19,5); NEU 19,5 x109/L (2-12,5); LYM 14,12 x109/L; MONO 1,96 x109/L (0,07-1,36); EOS 9,12 x109/L (0,06- 1,93); BASO 0,05 x109/L (0-0,1).
Clinically no evidence of polydipsia!
The charity agreed on taking biopsies (and subsequent histopathology) of the skin, spleen and enlarged lymph node.
Results – Histopathology
Spleen and inguinal lymphnode biopsy
(Dimitra Psalla, DVM, PhD)
Spleen: Multifocally white pulp is composed of atypical round cells with distinct cell borders, scant to moderate amphophilic cytoplasm, round to ovoid nuclei with finely stippled chromatin and one large basophilic nucleolus. There is moderate pleomorphism and mitoses average 1 per HPF. Multifocally red pulp is infiltrated by small numbers of neutrophils.
Inguinal lymphnode: Focal presence of atypical cells similar to those described above. Lymphnode is infiltrated by few neutrophils.
Diagnosis :Spleen and inguinal lymphnode: Infiltration by atypical round cells (accompanied by neutrophilic inflammation)
Comments: The diagnosis of lymphoma cannot be confirmed since the distribution of the atypical cells is limited on the white pulp and the pleomorphism is not high. This population could reflect a hyperplastic conditionas well.
Skin Biopsies – face, lateral body and dorsum
(Dimitra Psalla, DVM, PhD)
There is moderate irregular acanthosis that extends to follicular infundibula and is accompanied by mild spongiosis. Follicular isthmuses are severely infiltrated by the lymphocytes, histiocytes, neutrophils, and few eosinophils and multinucleated giant cells and the inflammatory infiltration is extending to the infundibulum. Parts of the follicular wall are widened due to accumulation of mucin (clear/basophilic spaces). Follicular atrophy is moderate to severe; normal anagen hair follicles are interspersed, particularly in less inflamed lesions. Moderate numbers of lymphocytes, histiocytes, neutrophils, and plasma cells surround hair follicles and infiltrate the superficial dermis. The histopathological features are similar in all the examined samples.
Diagnosis and Comments : The histopathological findings are compatible with the “Degenerative mucinotic mural folliculitis in cats”.
Picture 6 (6.1-6.3 pictures) Dimitra Psalla, DVM, PhD
Severely infiltrated Follicular isthmuses by the lymphocytes, histiocytes, neutrophils, and few eosinophils and multinucleated giant cells. Inflammatory infiltration is extending to the infundibulum. Accumulation of mucin. Follicular atrophy is moderate to severe. Moderate numbers of lymphocytes, histiocytes, neutrophils, and plasma cells surround hair follicles and infiltrate the superficial dermis.
Therapy continuation following the histopathology results:
The cat was started on oral prednisolone 3 mg/kg q24.Tapering off the prednisolone after 75% of the skin lesions had resolved and switching to cyclosporine, to avoid longer term adverse effects of corticosteroid treatment.
Picture 7(7.1-7.3 pictures) – One week after the start of prednisolone.
Supportive therapy included: Once weekly bathing with Clorexyderm ICF shampoo (4% chlorhexidine); Ectoparasite treatment with Stronghold plus (Zoetis) every 4 weeks; Purina Pro Plan veterinary diets HA Hypoallergenic and supplementing this with 4 drops YuMEGA cat once daily.
To stop the cat from reaching her skin and further self-mutilation, caused by the severe pruritus she was experiencing, she was dressed in a suit. She readily excepted the suit and wore it without any problem.
Picture 8(8.1-8.3 pictures) – Two weeks after the start of prednisolone.
Fur started regrowing on her head, body and legs.
There was a significant reduction in skin hyperpigmentation, scaling and crusting on the dorsum.
Gradually the pruritus decreased and the cat became more friendly, more active and was no longer apathetic.
After 3 weeks the prednisolone was tapered off gradually to an anti-inflammatory dose. (The oral prednisolone was decreased with 0.5 mg/kg every 5days, reaching 0,5 mg/kg q24h and finally after 5 days set on 0,5 mg/kg q48h).
Once the prednisolone dosage of 0,5 mg/kg q48h was reached, the cat was started on cyclosporine (suspension) 5mg/kg PO q24h simultaneously, for a duration of 10 days. Then the prednisolone was discontinued and the cyclosporine dosage increased to 7 mg/kg PO q24h.
Picture 9(9.1-9.5 pics.)Four weeks after the start of prednisolone.
Mila is much livelier and her fur is regrowing. However there are moments she is intensively licking herself, causing new skin lesions.
Picture 10(10.1-10.3 pics.)Two weeks after start of cyclosporin.
Mila while on cyclosporine – visibly improved. No more alopecia, no longer itchy and no new skin lesions.
Picture 11(11.1-11.6 pics.)Three weeks after start of cyclosporin.
Mila was feeling much better and was discharged after 12 weeks of inpatient care. She was now being cared for in a single-cat foster home. After discharging Mila she was monitored and followed up closely.
Mila was discharged and after two weeks came for her first check-up.
Picture 12 (12.1-12.4 pics.) Mila 2 weeks after discharging.
The cat progressed steadily, with normal fur regrowth on head, body, legs and tail. The skin of the dorsum was still very scaly.
The following supportive therapy was continued and slightly modified: Weekly washing with Clorexyderm 4% shampoo (ICF) , directly followed by washing with Allermyl (Virbac) shampoo. Topical treatment with Dermoscent Spot-on once weekly was added to the treatment protocol. Feeding Purina Pro Plan veterinary diets HA Hypoallergenic, but no longer supplementing with YuMEGA cat.
Picture 13(13.1-13.2 pics.) Mila in her foster home. Mila 8 weeks after discharging
The supportive therapy was continued and oral cyclosporine was reduced to 5 mg/kg q48h for another 2 months.
Her skin and coat were looking great and she was no longer itchy. She became active, friendly and very social.
Case Follow- up
Seven months after her last check-up Mila presented with dyspnoe. Diagnostics showed thoracic effusion and severe anemia. Thoracentesis was performed and she had several blood transfusions. However she didn’t improve. Feline Infectious Peritonitis was suspected. Eventually the decision was made to euthanize her.
I am particularly grateful for the cooperation with Dr. Rania Farmaki, Dp.ECVD, DVM and Dr. Dimitra Psalla, DVM, PhD. They provided me with invaluable advice and supported me throughout this difficult but interesting case. I would also like to thank the local charity Redom for their excellent care, trust and financial support. Finally, I wish to thank all my colleagues from the Central Veterinary Clinic in Sofia (Bulgaria) for their assistance.
Degenerative mucinotic mural folliculitis in cats- Gross TL, Olivry T, Vitale CB, Power HT. Vet Dermatol. 2001;12(5):279-8
Lymphocytic mural folliculitis and pancreatic carcinoma in a cat Remo Lobetti (Journal of Feline Medicine and Surgery 2015, 17 (6): 548-50)
Thymoma associated with exfoliative dermatitis in a cat. Jacqueline Vallim Jacobina Cavalcanti1, Mariana Pereira Moura1 and Fabio Oliveira Monteiro2 (Journal of Feline Medicine and Surgery 2014, Vol. 16(12) 1020– 1023)
First Case of Degenerative Mucinotic Mural Folliculitis in Brazil- Reginaldo Pereira de Sousa Filho, Veronica Machado Rolim, Keytyanne de Oliveira Sampaio, David Driemeier, Marina Gabriela Monteiro Carvalho Mori da Cunha, Fernanda Vieira Amorim da Costa
An anatomical classification of folliculitis-Gross LG, Stannard AA, Yager JA. Veterinary Dermatology. 1997;8147-156.