Subcutaneous granuloma annulare (SGA) is a rare skin condition that has overlapping features with rheumatoid nodules due to similar clinical and histological features. A 42-year-old female with a history of celiac disease and a family history of rheumatoid arthritis developed progressively painful nodules on her right hand. She was initially thought to have rheumatoid arthritis, but her serological markers were negative, and an incisional biopsy revealed palisaded granulomas with central mucin and necrobiotic collagen that led to a diagnosis of SGA. Differentiating between these two conditions is important because rheumatoid nodules require immunosuppressive therapy due to systemic inflammation, while SGA is a self-limiting benign condition. This case highlights the need for a biopsy of atypical subcutaneous nodules and the importance of combining clinical, pathological, and interdisciplinary expertise to ensure accurate diagnosis and the best patient care.

Pancreatic panniculitis is a rare cutaneous manifestation of pancreatic disease, most commonly occurring in patients with acute or chronic pancreatitis or pancreatic neoplasms. In most reported cases, pancreatic pathology is recognized before or concurrent with the onset of skin lesions; less commonly, panniculitis precedes the diagnosis. Histology demonstrates a lobular panniculitis with saponified fat necrosis and anucleate "ghost" adipocytes, findings that are pathognomonic. Clinically, pancreatic panniculitis presents as tender subcutaneous nodules, most often on the lower extremities, and may be accompanied by systemic manifestations such as fever and inflammatory arthritis. We report 2 cases of pancreatic panniculitis occurring in patients without abdominal pain.

Blastomycosis is a dimorphic fungal infection caused by Blastomyces dermatitidis and related species, classically presenting with pulmonary and cutaneous involvement. Musculoskeletal manifestations, particularly monoarthritis, are rare and diagnostically challenging. We present the case of a previously healthy 41-year-old man who developed nodular skin lesions, cough, pulmonary nodules and persistent left knee arthritis, initially thought to be due to pseudogout. The diagnosis of disseminated fungal infection was suggested by CT scan, skin biopsy, and confirmatory fungal culture that grew Blastomyces dermatitidis. This case highlights the atypical pattern of joint involvement, the need to expand the differentials as dictated by clinical signs, the role of multidisciplinary collaboration, and the diagnostic utility of skin biopsy and fungal culture.

Dupuytren's disease is a fibroproliferative disorder of the palmer fascia (PF) characterised by flexion contractures in the hand. Dupuytren's disease can be treated surgically, but disease recurrence rates are high, potentially due to continual production of matrisomal proteins. Here, metabolic labelling and proteomics identified differences in the new synthesis and composition of matrisomal proteins between Dupuytren's tissue and normal PF. Dupuytren's tissue actively synthesised type I collagen, fibronectin (FN1), matrix metalloproteinases-2 and -3 (MMP2, MMP3) and tissue inhibitor of metalloproteinases 2 (TIMP2). Both tissues actively synthesised insulin-like growth factor binding protein 7 (IGFBP7). Label-free analysis implicated the transforming growth factor-β (TGFβ) pathway in the matrisomal profile of Dupuytren's tissue. The effect of TGFβ isoforms on COL1 mRNA expression was first tested in cultured young and aged equine tenocytes. COL1A1 mRNA responded to treatment with all TGFβ isoforms and was more highly expressed in cells from aged samples. In aged human cells, COL1A1 and COL1A2 mRNA was higher in cells derived from Dupuytren's tissue than normal PF and in response to TGFβ1, but no changes in COL1A1 or COL1A2 CpG methylation were detected. TGFβ1 treatment only resulted in increased type I collagen protein accumulation in the media of Dupuytren's nodule cells. In three-dimensional cultures, COL1A1 mRNA was lower in normal PF than in Dupuytren's cells, but TGFβ1 treatment only increased type I collagen accumulation in the media of normal PF cultures, and TGFβ1 inhibition did not alter new collagen protein synthesis. TGFβ1 inhibition in Dupuytren's tissue explants did not alter the proportion of homotrimeric type I collagen, nor was this changed in skin or tendon of the tight-skin (TSK) mouse, a naturally occurring model of indirect TGFβ1 activation. Therefore, the role of TGFβ in Dupuytren's disease may be predominantly related to myofibroblast phenoconversion and contractility rather than directly altering collagen protein synthesis. © 2026 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

A 58-year-old man presented with an enlarging painful ulcer on his left medial knee. He had a history of psoriatic arthritis, treated with methotrexate and adalimumab for the last 5 years. He had travelled to over 20 countries in the past 2 years, and his hobbies included scuba diving and seawater/freshwater swimming. He recalled freshwater swimming in a cave lake in Brazil 1 year prior. Subsequently, he developed small erythematous papules on each knee with rapid resolution on the right knee. The left knee lesion slowly enlarged, and he sought medical attention in Ireland 9 months later. He received antibiotics and topical steroids, and was switched from adalimumab to infliximab for a presumed diagnosis of pyoderma gangrenosum. The lesion's growth accelerated over 8 weeks, leading to an acute presentation to the Emergency Department with severe pain and limited mobility. On examination, he had a 20 × 10 cm erosive plaque on his left knee with an exudative base and a ragged erythematous edge. He also had a 2.5 × 2 cm ulcerative lesion on his right flank and a hyperpigmented patch on his right knee. He denied fevers or systemic symptoms. Interferon-γ release assay was positive. A skin biopsy from the left leg demonstrated ulceration, mixed inflammation and underlying dermal necrosis. Necrotizing granulomas were seen, and both auramine and Ziehl-Neelsen stains were positive for abundant acid-fast bacilli. Skin biopsy from the right flank showed similar findings. A mycobacterial culture was incubated at 30°C and after 4 weeks, Mycobacterium marinum was identified. Mycobacterium marinum is a free-living, slow-growing, nontuberculous mycobacterium found in cold and warm fresh and saltwater environments. It can cause a tuberculosis-like disease in fish and can opportunistically infect humans when injured skin is exposed to a contaminated aqueous environment. The typical presentation is a 'fish tank granuloma': nodules, plaques or ulcerated lesions that spread in a sporotrichoid pattern along lines of lymphatics, commonly on the upper limb. This case represents a highly unusual cutaneous M. marinum presentation, with noncontiguous ulcerative lesions in an immunocompromised host. The diagnostic delay highlights the challenges of recognizing atypical nontuberculous mycobacterial infections, particularly in patients who are immunosuppressed.

Lofgren syndrome is an acute and pathognomonic form of sarcoidosis characterized by fever, hilar lymphadenopathy, arthritis, and erythema nodosum (EN). We report a 35-year-old female patient from Ethiopia who presented with a 4-day history of arthritis involving bilateral ankles, knees, and wrists associated with fever and skin lesions typical of EN. Chest imaging (X-ray and computed tomography (CT) scan) revealed bilateral hilar and mediastinal lymphadenopathy as well as perilymphatic nodules in the mid and upper zones of both lungs. Workup for alternative diagnoses, including tuberculosis, was negative. After the diagnosis of Lofgren syndrome was made, she was started on a low dose of prednisolone, which resulted in a prompt and marked improvement in her symptoms.

An 82-year-old man with a history of hypertension, thyroid nodule, and parkinsonism on carbidopa/levodopa was referred for a sudden eruption of scattered purpuric macules. He noted fatigue, weakness, ankle swelling, abdominal fullness, headaches, lapses in memory, and dysphasia. On physical examination, he had thin and atrophied upper extremities and central obesity, as well as nonblanching red to purple macules on the lower abdomen and ecchymosis on bilateral arms. The patient denied the use of any corticosteroids. Lab workup showed an abnormally high post-dexamethasone cortisol level, which raised suspicion for Cushing syndrome. Further inquiry into the patient's medication and supplement history revealed that he was consuming Artri King, a supplement marketed for the treatment of joint pain and arthritis. Artri King can lead to numerous dermatological manifestations akin to endogenous Cushing syndrome such as thin skin, easy bruising, and purple striae. This case illustrates the potential risks of over-the-counter dietary supplements, which often circumvent the strict Food and Drug Administration regulations applied to prescription medications, posing significant health hazards to users. There is critical need for transparency and regulation of supplements.

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease characterized by painful nodules, abscesses, and draining tunnels in areas such as the axillae, groin, and inframammary regions. It typically emerges in early adulthood, with a global prevalence of approximately 1%, though regional variations exist. HS significantly affects patients' quality of life and imposes considerable socioeconomic burdens. It is frequently associated with metabolic syndrome, inflammatory arthritis, and inflammatory bowel disease, reflecting its underlying systemic inflammatory nature. The pathogenesis of HS involves innate immune mechanisms, including macrophages, neutrophils, interleukin (IL)-1β, tumor necrosis factor-alpha (TNF-α), and granulocyte colony-stimulating factor, alongside adaptive immune responses mediated by T cells (IL-17, interferon-gamma [IFN-γ]) and B cells, which contribute to autoantibody formation and tertiary lymphoid structures. Chronic inflammation results in irreversible tissue damage, tunnel formation, and severe scarring. Treatment strategies vary based on disease severity. Early inflammatory stages benefit from pharmacological therapies, while later stages require a combination of medical and surgical interventions, with surgery often necessary for advanced cases. The introduction of targeted biologic therapies, including TNF-α (adalimumab) and IL-17 inhibitors (secukinumab, bimekizumab), has expanded treatment options beyond traditional antibiotic regimens. Effective management focuses on early intervention to prevent irreversible damage, control symptoms such as pain, and address systemic comorbidities. A timely diagnosis, along with a multidisciplinary and personalized approach, is essential for improving patient outcomes and quality of life.

Cutaneous nocardiosis is an uncommon but clinically significant opportunistic infection, primarily affecting immunocompromised individuals, including those with underlying malignancies, organ transplants, or chronic corticosteroid use. Although it can also occur in elderly patients, this is often due to age-associated immunosenescence or comorbid conditions that impair immune function. We describe a case of lymphocutaneous Nocardia brasiliensis infection in an 87-year-old man with no history of trauma or corticosteroid use. The patient had been receiving long-term low-dose methotrexate (MTX) for rheumatoid arthritis. He presented with painful, erythematous nodules arranged along the lymphatic vessels of the right forearm. Histopathological analysis and culture confirmed the diagnosis. Oral trimethoprim-sulfamethoxazole (TMP-SMX) and minocycline were initiated; minocycline was discontinued after three weeks due to gastrointestinal symptoms. MTX was also stopped in response to clinical progression. The lesions resolved completely with continued TMP-SMX monotherapy over a three-month course. A brief review of the literature revealed only a few reported cases of cutaneous nocardiosis in individuals over 85 years of age. Some of these lacked clear immunosuppressive backgrounds or trauma history. While TMP-SMX remains the standard therapy, its use in older adults may be constrained by tolerability. This case serves as a reminder that Nocardia infection should be considered in the differential diagnosis of nodular skin lesions in very elderly patients, even in the absence of typical risk factors.

A 50-year-old patient presented to his family doctor with pain and livid, subcutaneous nodules on the right hand.Laboratory chemistry and native radiologic examinations were unremarkable. An attempt at NSAID therapy was unsuccessful. On the basis of the clinical picture, immunomodulating therapy was carried out on suspicion of rheumatoid arthritis.Due to significant clinical worsening, hand surgery was needed and MM was detected by biopsy.Combination antimycobacterial therapy was initiated. Four months later, visual disturbances and polyneuropathy occurred. The cause was a supratherapeutic dose of ethambutol. After a change in therapy had been carried out, almost a complete regression of symptoms could be achieved.Infectious diseases with a low local prevalence, for example caused by non-tuberculous mycobacteria, and their therapeutic management should be left to treatment centers with a high level of infectiological expertise. When treating unselected patients with unclear skin lesions, the question of aquarium exposure should be raised.