Diagnosing Uncommon Dermatoses in Children: LCH, Psoriasis, and More

When a pediatric patient has cycled through multiple providers without a diagnosis, the problem is rarely that the condition is extraordinarily rare.¹ More often, a common disease is presenting atypically, and accumulated diagnostic assumptions are standing in the way. That distinction shapes how Dawn Eichenfield, MD, PhD, of Rady Children's Health, approaches the most diagnostically challenging cases in her practice.²

Eichenfield presented “Outside the Box: Treating the Uncommon Dermatosis” at Maui Derm NP+PA Summer 2026 in Colorado Springs on June 25. Her session addressed the clinical features that signal an atypical presentation, the role and limits of biopsy, and how to build a treatment rationale when controlled trial data are unavailable.

In the Q&A below, Eichenfield discusses dermatologic conditions most prone to misdiagnosis, including Langerhans cell histiocytosis (LCH), perianal streptococcal dermatitis, and hormonally driven acne. She also outlines the mindset shift she wants clinicians to leave with: when a disease does not behave as expected, reassess the diagnosis rather than escalate treatment under the same assumption.

HCPLive: When a patient arrives at your clinic having already seen multiple providers without a diagnosis, what is your general approach to working through a differential for a rare or uncommon dermatosis?

Eichenfield: My first step is to revisit the history and physical examination with fresh eyes and challenge the assumptions that may have accumulated along the diagnostic journey. In pediatric dermatology, uncommon diseases are often not rare diseases—they are common diseases presenting atypically. In acne, I consider whether the presentation is consistent with typical adolescent acne or whether endocrine, medication-induced, genetic, or syndromic factors warrant investigation.

HCPLive: Are there particular clinical features or patterns that prompt you to think "this is outside the usual" early in an encounter?

Eichenfield: Absolutely. In diaper dermatitis, red flags include ulceration, purpura, erosions, refractory disease despite appropriate barrier care, involvement outside the diaper area, systemic symptoms, failure to thrive, or unusual age of presentation. Findings such as sharply demarcated plaques, persistent perianal disease, or recurrent infections may suggest alternative diagnoses such as psoriasis, Langerhans cell histiocytosis, nutritional deficiency, inflammatory bowel disease, or immunodeficiency.

HCPLive: How much does biopsy inform your diagnosis versus clinical presentation alone, and where does biopsy tend to fall short?

Eichenfield: Most pediatric dermatologic diagnoses remain fundamentally clinicopathologic correlations, with the clinical examination driving the diagnosis. Biopsy can be extremely helpful when considering rarer entities such as Langerhans cell histiocytosis. However, biopsies often provide pattern recognition rather than a definitive answer. The pathology report must always be interpreted within the broader clinical context.

HCPLive: Are there uncommon dermatoses that are especially prone to mimicking more common conditions, and how do you avoid anchoring on the wrong diagnosis?

Eichenfield: Many are. Langerhans cell histiocytosis can resemble refractory diaper dermatitis. Psoriasis may be mistaken for candidiasis. Perianal streptococcal dermatitis can be misdiagnosed as irritant dermatitis. Zinc deficiency may mimic severe eczema or persistent diaper rash.

Similarly, endocrine-driven acne can initially resemble routine adolescent acne. Avoiding anchoring requires reassessing the diagnosis whenever the disease behaves differently than expected. Failure of an appropriate therapy should prompt reconsideration rather than escalation of treatment under the same diagnostic assumption.

HCPLive: For a general dermatologist who may only see one or two of these cases per year, what is the most important shift in mindset or approach you want them to leave this session with?

Eichenfield: The most important lesson is to pay attention when a disease does not behave as expected. Most missed diagnoses occur not because a condition is extraordinarily rare, but because we continue treating a presumed diagnosis despite evidence that it may be incorrect. Reassessing the diagnosis, broadening the differential, and seeking additional expertise early can substantially improve outcomes.

References

1. Onsoi W, Chaiyarit J, Techasatian L. Common misdiagnoses and prevalence of dermatological disorders at a pediatric tertiary care center. J Int Med Res. 2020;48(2):300060519873490. doi:10.1177/0300060519873490

2. Eichenfield D. Outside the Box: Treating the Uncommon Dermatosis. Session presented at Maui Derm Summer 2026 in Colorado Springs on June 25.