Investigations
1st investigations to order
dermoscopy
Test
Confirmatory test of the disease; to differentiate from guttate psoriasis[18]
Result
orange-yellowish structureless areas, focal dotted vessels, and non-dotted vessels
skin biopsy
Test
Histopathological examination confirms the disease.[4]
Specimens may also be analysed for clonality with next-generation sequencing of T-cell receptor beta and gamma genes.[20][21]
Result
pityriasis lichenoides et varioliformis acuta: wedge-shaped, dense, and diffuse dermal CD8+ predominant lymphocytic infiltrate. Epidermal apoptotic and necrotic keratinocytes, neutrophilic inclusions, spongiosis, and focal parakeratosis. Next-generation sequencing may be positive for T-cell clonality. Pityriasis lichenoides chronica: superficial CD4+ T-dominant lymphocytic, band-like, sparsely perivascular infiltrate. Slight parakeratotic scale, minimal keratocytic necrosis, and spongiosis in the epidermis. Febrile ulceronecrotic Mucha-Habermann disease: prominent lymphocytic and neutrophilic infiltrate, pronounced epidermal necrosis and ulceration, and leukocytoclastic vasculitis
Investigations to consider
anti-streptolysin titres
Test
Consider checking if clinically suspecting infectious origin or severe ulceronecrotic form of disease.[4]
Result
to exclude streptococci
Epstein-Barr virus IgM/IgG viral capsid antigen and nuclear antigen antibody
Test
Consider checking if clinically suspecting infectious origin or severe ulceronecrotic form of disease.[4]
Result
to exclude Epstein-Barr virus
monospot or heterophil antibody test
Test
Consider checking if clinically suspecting infectious origin or severe ulceronecrotic form of disease.[4]
Result
to exclude Epstein-Barr virus
hepatitis B surface antigen, anti-surface antibody, and anti-core IgM
Test
Consider checking if clinically suspecting infectious origin or severe ulceronecrotic form of disease.[4]
Result
to exclude hepatitis B
hepatitis C virus antibody
Test
Consider checking if clinically suspecting infectious origin or severe ulceronecrotic form of disease.[4]
Result
to exclude hepatitis C
HIV screening
Test
Consider checking if clinically suspecting infectious origin or severe ulceronecrotic form of disease.[4]
Result
to exclude HIV
rapid plasma reagin
Test
Consider checking if clinically suspecting infectious origin or severe ulceronecrotic form of disease.[4]
Result
to exclude syphilis
throat cultures
Test
Consider checking if clinically suspecting infectious origin or severe ulceronecrotic form of disease.[4]
Result
to exclude bacterial aetiology
toxoplasma Sabin-Feldman's dye test, indirect immunofluorescence/haemagglutination
Test
Consider checking if clinically suspecting infectious origin or severe ulceronecrotic form of disease.[4]
Result
to exclude toxoplasmosis
erythrocyte sedimentation rate
Test
Consider checking if clinically suspecting infectious origin or severe ulceronecrotic form of disease.[4]
Result
elevated in febrile ulceronecrotic Mucha-Habermann's disease
CRP
Test
Consider checking if clinically suspecting infectious origin or severe ulceronecrotic form of disease.[4]
Result
elevated in febrile ulceronecrotic Mucha-Habermann's disease
serum LDH
Test
Consider checking if clinically suspecting infectious origin or severe ulceronecrotic form of disease.[4]
Result
elevated in febrile ulceronecrotic Mucha-Habermann's disease
WBC count
Test
Consider checking if clinically suspecting infectious origin or severe ulceronecrotic form of disease.[4]
Result
leukocytosis in febrile ulceronecrotic Mucha-Habermann's disease
serum albumin
Test
Consider checking if clinically suspecting infectious origin or severe ulceronecrotic form of disease.[4]
Result
hypoalbuminaemia in febrile ulceronecrotic Mucha-Habermann's disease
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