Case 1 History
A 38-year-old female presents with a 2-week history of painful red nodules on the bilateral anterior shins. She reports she experienced similar nodules 1 year prior with concurrent fever and malaise, with complete resolution within 1 month.
Microscopic Findings
Sections show septal inflammation with lymphocytes, macrophages, and multinucleated giant cells ( Fig. 8.1 ).
Diagnosis
Erythema Nodosum
Clinical Presentation
Erythema nodosum (EN) is the most common type of panniculitis and is associated with a wide variety of triggering stimuli (see Table 8.1 for a list of clinical associations). Typically, EN presents as erythematous to purple nodules with a bruise-like appearance. The duration of a bout is typically several weeks. There is no associated ulceration, and resolution typically occurs without scarring. Concurrent fever and malaise are characteristic, and recurrences are common, as was observed in this case.
| Erythema Nodosum | Deep Granuloma Annulare | Necrobiosis Lipoidica | Rheumatoid Nodule | |
|---|---|---|---|---|
| Clinical association | Numerous, including sarcoidosis (SORE SHIN) a | None | Diabetes | Rheumatoid arthritis |
| Typical location on body | Anterior shins | Upper and lower extremities | Shins | Near joints |
| Location of infiltrate | Septal and paraseptal panniculus | Dermal and subcutaneous | Dermal and subcutaneous | Dermal and subcutaneous |
| Intervening material | None, though septal fibrosis occurs | Mucin | Degenerated collagen | Fibrin (pink to red) |
a Associations with erythema nodosum
- 1.
S treptococci and sarcoidosis
- 2.
O ral contraceptives, pregnancy
- 3.
R ickettsia
- 4.
E ponym (Behçet disease)
- 5.
S ulfonamides
- 6.
H ansen disease
- 7.
I nflammatory bowel disease
- 8.
N on-Hodgkin lymphoma
- 9.
S arcoidosis
Histopathology
The microscopic configuration varies depending on chronicity. Early involvement shows septal edema with neutrophils and purpura. As the disease progresses, the septa become thickened and fibrotic. The inflammatory infiltrate contains lymphocytes, eosinophils, and histiocytes, including multinucleated cells with clefts (so-called Miescher granulomas ). A Miescher granuloma represents a tiny focus of lipomembranous fat necrosis. Vasculitis is not a significant component.
Differential Diagnosis
Given that the septal inflammatory infiltrate in EN is largely histiocytic, the differential diagnosis is limited. It includes other granulomatous diseases, such as granuloma annulare, necrobiosis lipoidica, and rheumatoid nodule, which are discussed elsewhere. Key differences are highlighted in the Table 8.1 . With increasing application of immune checkpoint inhibitor therapy in cancer care, it is important to note that an EN-like or subcutaneous sarcoidal pattern of inflammation has been described as an immune-related adverse event in that therapeutic context (see Table 8.1 ).
Case 2 History
The patient is a 48-year-old male with history of alcohol abuse who presents with stomach pain and painful red nodules on the shins and buttocks. One nodule is ulcerated, with oily drainage. He also reports bilateral ankle pain.
Microscopic Findings
Biopsy sections of a nodule show subcutaneous tissue with lobular inflammation with fat necrosis and cystic degeneration ( Fig. 8.2 ). The inflammatory infiltrate is mixed, composed of neutrophils, foamy histiocytes, and lymphocytes. There scattered foci at the periphery of the necrotic areas showing pale basophilic debris (“saponification”).
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