Mitragyna speciosa, a tree of the Rubiaceae family native to Southeast Asia, is the plant used in kratom products. Traditional use involves chewing fresh leaves or brewing them into tea, whereas modern products are marketed as loose powders, capsules, tablets, and other formulations. Kratom use has increased in recent years and is an underrecognized cause of hyperpigmentation, which is hypothesized to result from alkaloid-mediated activation of dopamine receptors, leading to melanocyte activation. Recognition of this uncommon adverse effect is increasingly important, as dermatologists should consider kratom use in patients presenting with unexplained photodistributed or drug-induced hyperpigmentation.

We present a clinicopathological challenge involving a persistent truncal eruption in a patient with Waldenström macroglobulinemia. Clinical examination showed erythematous to violaceous macules and plaques, and biopsy demonstrated a dermal lymphoplasmacytic infiltrate with IgM/κ restriction. Molecular analysis identified MYD88 L265P in the cutaneous specimen. Integration of the clinical history, immunophenotype, clonality studies, and molecular findings supported secondary cutaneous lymphoplasmacytic lymphoma rather than cutaneous macroglobulinosis, primary cutaneous marginal zone lymphoma, or drug eruption.

Severe cutaneous adverse reactions are rare, potentially life-threatening T-cell-mediated drug reactions. They present with rapid onset skin lesions and may involve the mucosa and multiple organs. This review finds that early identification, drug withdrawal, supportive care, and immunomodulatory therapy are essential. JAK inhibitors have shown promise in Stevens-Johnson's syndrome/toxic epidermal necrolysis, IL-5 blockade is being tested for drug reaction with eosinophilia and systemic symptoms; and IL-36 inhibition, may be a future option for acute generalised exanthematous pustulosis.

Adult-onset Still's disease (AOSD) is a diagnosis of exclusion and may be difficult to recognize when infection and drug hypersensitivity coexist. A 31-year-old woman presented with high-spiking fever, arthralgia, and a generalized eruption after ampicillin exposure. Initial investigations for infection and autoimmune disease were unrevealing. Her clinical course was subsequently complicated by severe nosocomial infection and recurrent eruptions during antibiotic treatment. Recurrent high-spiking fever and a fever-associated eruption after apparent clinical improvement of infection supported AOSD as the working diagnosis. However, uncertainty regarding the rash and overlapping infectious and drug-related features limited confident retrospective confirmation of the Yamaguchi classification criteria. Following infection control, intravenous methylprednisolone pulse therapy followed by cyclosporine resulted in rapid clinical improvement. This case illustrates the diagnostic complexity of AOSD in the setting of nosocomial infection and antibiotic hypersensitivity.

Biologic therapies are highly efficacious for pediatric atopic dermatitis (AD) and psoriasis (PsO); however, their expanding use has led to increased reports of phenotype switching-a paradoxical condition where biologics induce new-onset immune-mediated dermatoses. To address clinical uncertainty regarding these complex reactions, this review evaluates real-world case reports, case series, and observational studies of pediatric AD and PsO patients who developed phenotypic switching during biologic therapy. Dupilumab is the most frequently implicated agent, commonly inducing psoriasiform, pustular, or palmoplantar eruptions in AD patients via a compensatory shift from Th2- to Th17-predominant immunity. Conversely, phenotype switching from IL-12/23 and TNF-α inhibitors remains rare in pediatric dermatology. For severe, refractory cases or AD-PsO overlaps, Janus kinase (JAK) inhibitors demonstrate significant rescue efficacy, provided appropriate baseline and ongoing laboratory monitoring is maintained. Pediatric patients experiencing biologic-induced phenotype switching can be successfully managed in clinical practice through early recognition and the implementation of the practical, evidence-based treatment algorithm proposed in this review.