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Presentation

Learning from Diagnostic Mistakes: Generalized Pustular Psoriasis and Sala Syndrome Cases

Description

The speaker presents two dermatology cases to highlight diagnostic mistakes and the importance of clinicopathologic correlation. In the first case, a woman with a long-standing burning, generalized pustular eruption was initially mistaken for Sneddon-Wilkinson syndrome and treated with dapsone without benefit, but colleagues later helped identify chronic generalized pustular psoriasis (GPP). The talk explains how GPP can mimic impetigo, AGEP, palmoplantar pustulosis, and subcorneal pustular dermatosis, and emphasizes clues such as burning rather than itching, psoriasiform scale, dotted vessels on dermoscopy, and supportive histology. The speaker notes that GPP has many forms, can be severe and disabling, and now has more appropriate treatment options. In the second case, a patient with Sala syndrome, a rare inherited lysosomal storage disorder caused by SLC17A5 mutations, had unusual scalp lesions resembling “puppy paw pads.” Dermoscopy was nonspecific, biopsy showed dermal space suggesting deposited material, and Alcian blue stain confirmed mucin. The lesions were painful and managed with serial excisions. The overall message is to stay open to atypical presentations, revisit prior assumptions, and learn from mistakes to improve patient care.

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Conclusions

Generalized pustular psoriasis can present in chronic, atypical forms that are easy to misdiagnose as other pustular dermatoses.
Clinical-pathologic correlation is essential because histology and bedside features together can reveal the correct diagnosis when either alone is misleading.
Burning pain, widespread sterile pustules, psoriasiform scale, and dotted vascular patterns are clues that favor generalized pustular psoriasis over Sneddon-Wilkinson syndrome.
Generalized pustular psoriasis is a severe, unpredictable disease that can significantly impair quality of life and may increase mortality risk if not treated appropriately.
A patient’s lack of response to therapies for a presumed alternative diagnosis should prompt reconsideration of the diagnosis and treatment plan.
Dermoscopic findings such as collarette scale and dotted vessels can help identify psoriasis in challenging pustular eruptions.
Rare inherited storage disorders like Salla syndrome can present with unusual, painful scalp papules and require special stains such as Alcian blue to identify mucinous deposits.
Unusual clinical presentations should broaden the differential and encourage targeted biopsy interpretation and stain selection.
The presenter’s main takeaway is that clinicians should remain humble, revisit earlier cases, and correct mistakes so patients receive more appropriate care.

Michelle Tarbox, MD. Clinicopathologic Self-Assessment. Associate Professor of Dermatology and Dermatopathology. Texas Tech University Health Sciences Center.
https://www.pcds.org.uk/
Munro microabscesses and spongiform pustules of Kogoj.
Periodic acid–Schiff (PAS), Oil Red O, Congo red, Alcian blue (pH 2.5), and Von Kossa.