Dermatitis herpetiformis (DH) and linear IgA disease

·       Dermatitis Herpetiformis

Definition

Dermatitis herpetiformis (DH) is an unusual autoimmune cutaneous eruption related to gluten sensitivity. Affected patients commonly develop intensely pruritic inflammatory papules and vesicles on the forearms, knees, scalp, or buttocks. The majority of patients with DH have an associated gluten-sensitive enteropathy (celiac disease) as well. In most of these patients, the enteropathy is asymptomatic.

Panel test

·        Immunogenetics:

o   Increased incidence of HLA-A1/B8/DR3/DQw2 and associated organ- specific autoimmune disease.

·        Immunopathology:

o  DIF on the skin biopsy shows typical granular IgA deposits on the dermal papillae.

o  Jejunal/duodenal biopsies will often show features of coeliac disease even in the absence of clinical symptoms.

·        Autoantibodies:

o   IgA endomysial or tissue transglutaminase antibodies will be positive.

comments: Gluten-free diet will eventually lead to resolution of the rash.

Resistant cases may require treatment with dapsone, having first excluded G6PD deficiency (monitor all patients for haemolysis and methaemoglobinaemia.

References:

1. Salmi TT, Hervonen K, Kautiainen H, et al. Prevalence and incidence of dermatitis herpetiformis: a 40-year prospective study from Finland. Br J Dermatol 2011; 165:354.

· Linear IgA Disease

Definition:

Linear IgA bullous dermatosis (LABD), also known as linear IgA disease, is a rare, idiopathic or drug-induced autoimmune blistering disease described by the linear deposition of IgA at the dermoepidermal junction. In spite of the clinical manifestation of this disorder is difficult to diagnose from dermatitis herpetiformis, the different immunopathologic findings in LABD and the lack of an associated gluten-sensitive enteropathy approbate the status of LABD as a separate disease.

Panel test:

·        Immunopathology:

o   DIF shows linear (rather than granular) IgA deposition along the basement membrane, and a 97kDa antigen (LAD-1) has been detected in most cases.

·        Autoantibodies:

o   Antibody against to a domain of the BPAg2 antigen (180kDa).

References:

1. Fortuna G, Marinkovich MP. Linear immunoglobulin A bullous dermatosis. Clin Dermatol 2012; 30:38.
2. Mintz EM, Morel KD. Clinical features, diagnosis, and pathogenesis of chronic bullous disease of childhood. Dermatol Clin 2011; 29:459.
3. Gluth MB, Witman PM, Thompson DM. Upper aerodigestive tract complications in a neonate with linear IgA bullous dermatosis. Int J Pediatr Otorhinolaryngol 2004; 68:965.
4. Zhao CY, Chiang YZ, Murrell DF. Neonatal Autoimmune Blistering Disease: A Systematic Review. Pediatr Dermatol 2016; 33:367.