Dermoscopic findings and comparison of usefulness of longitudinal versus transversal sections in the histological diagnosis of alopecia X.

BACKGROUND: A combination of dermoscopic and histological findings may provide useful information for the diagnosis of hair follicle diseases. However, there are no studies on dermoscopic-histopathological correlations in dogs affected by alopecia X, and comparison of longitudinal versus transversal sectioning of skin biopsy specimens in the assessment of this hair loss disorder has not been thoroughly investigated. HYPOTHESIS/OBJECTIVES: The aim of this study was to correlate dermoscopic and histological features using both longitudinal and transversal sectioning of skin biopsy samples to gain additional information for the diagnosis of alopecia X. ANIMALS: Nineteen Pomeranian dogs affected by alopecia X and five healthy Pomeranians as controls. MATERIALS AND METHODS: Dermoscopic-histological correlation was performed within the diseased group, whereas histological comparisons against controls. The demographic and clinical characteristics also were related to the histological findings. RESULTS: The dermoscopic findings revealed scattered, thinned, short hairs mixed with amorphous keratoseborrhoeic-like material (follicular plugging), perifollicular and intrafollicular scaling, and hyperpigmentation varying from pinpoint black spots to a diffuse texture. Dermoscopic findings correlated with histological findings for selected qualitative and quantitative findings. The usefulness of transversal sections was demonstrated in accurately determining the hair follicular density and counts, growth arrest phases and in identifying mineralisation of hair follicle basement membrane when compared to the longitudinal. Conversely, no correlations between histological findings and demographic and clinical characteristics were detected. CONCLUSIONS AND CLINICAL RELEVANCE: These data provide evidence of the usefulness of dermoscopic evaluation as an accessory diagnostic tool and of transversal sections of skin biopsies as complementary to the diagnosis of alopecia X.

Heterozygous ATP2A2 missense variant identified in a Shih Tzu with Darier disease.

Darier disease is caused by heterozygous loss of function variants in the ATP2A2 gene encoding the endoplasmic/sarcoplasmic reticulum Ca2+ pump ATP2A2. Defective intracellular calcium signaling in the epidermis results in a loss of desmosomal adhesion and the development of characteristic skin lesions. In this study, we investigated a Shih Tzu that developed erythematous papules on the ventrum and, over time, the dorsal neck and a nodule in the right ear canal with secondary ear infection. Histopathologic examination demonstrated discrete foci of acantholysis affecting suprabasal layers of the epidermis. Whole genome sequencing of the affected dog identified a heterozygous missense variant, p.N809H, affecting an evolutionarily conserved amino acid residue of the ATP2A2 protein. The highly characteristic clinical and histopathologic findings together with a plausible variant in the only known functional candidate gene establish the diagnosis of canine Darier disease in the studied dog and highlight the potential of genetic analyses as complementary diagnostic approach in veterinary medicine.