A 73-year-old man presented to the Dermatology Department with asymptomatic skin lesions on the trunk of 4 weeks’ duration, accompanied by mild hyporexia without other symptoms. The lesions did not respond to high-potency topical corticosteroids. The patient reported no recent drug initiation or significant sun exposure. His past medical history included locally advanced laryngeal carcinoma treated with chemoradiotherapy 3 years earlier.

Large, asymptomatic erythematous patches were observed, neither elevated nor depressed on palpation, distributed over the upper back and anterior trunk, sparing the face and extremities. The lesions were arranged in a reticulated pattern, with no additional relevant findings (Fig. 1). No lymphadenopathy was detected.

Fig. 1

Histological examination revealed a “busy” dermis with interstitial infiltrates composed of histiocytes, some lymphocytes, and occasional multinucleated giant cells. These cells were intercalated between collagen bundles and around vessels. In addition, separation of collagen bundles with interstitial mucin deposition was observed. The epidermis was normal. No atypical lymphocytes were identified in the epidermis or dermis (Fig. 2).

Fig. 2

Blood tests showed a mild elevation of liver enzymes without other abnormalities, and autoimmune markers were negative. Dyslipidemia was ruled out. No imaging modalities were initially indicated.

What is your diagnosis?

Patch-type granuloma annulare.

The patient was hospitalized 2 months later due to pneumonia associated with progressive weight loss over the previous month. Blood tests revealed leukocytosis (53,700leukocytes/μL) with monocytosis (41,200monocytes/μL). A peripheral blood smear, bone marrow biopsy, and flow cytometry were performed, all consistent with acute myelomonocytic leukemia. The patient subsequently died during hospitalization due to complications related to the respiratory infection.

Granuloma annulare (GA) is a common benign disorder of unknown etiology, with an estimated incidence of 0.1–0.4%.1 It typically presents as localized papules or plaques (classically acral), although a disseminated or generalized form – often associated with a more recalcitrant course – may also occur.1 Less frequent variants include subcutaneous, patch (as in the present case), perforating, and a recently described ulcerative form.2

GA has been traditionally associated with several systemic conditions. The most widely recognized association is with diabetes mellitus; however, autoimmune thyroiditis, dyslipidemia, and infections such as HIV or hepatitis B and C have also been linked to this condition.3

The association between GA and malignancy remains controversial, as the available literature is conflicting, likely due to small sample sizes in reported studies.3–5 However, a recent cohort study of 48,132 patients demonstrated a significantly increased risk of lymphoma, leukemia, and hematologic malignancies in patients with GA compared with controls.6 One limitation of this study was the inability to stratify by GA subtypes. Such stratification would be particularly valuable to determine whether generalized or other uncommon clinical variants are associated with a higher risk of underlying malignancy, a hypothesis previously suggested by other authors.4

Regarding differential diagnosis, mycosis fungoides should be considered, as it may initially present as disseminated patches, particularly in sun-protected areas. Dermatomyositis should also be considered, given the clinical resemblance to the “shawl sign” and its known association with malignancy.

In conclusion, we present a case of generalized GA manifesting as patches and preceding the diagnosis of acute myelomonocytic leukemia, highlighting the potential association between GA and underlying hematologic malignancies. This association should be particularly considered in elderly patients presenting with generalized, refractory, or uncommon variants of GA, especially when additional risk factors for leukemia are present, such as prior chemoradiotherapy.

The authors declare no conflict of interest.