What's causing these skin blisters?

An enzyme deficiency leads to photosensitivity and fragile skin

Janet, 57, presents with a six-month history of recurrent blisters on the dorsum of her hands and feet.

She develops a new blister every few days.

The lesions are tender and non-pruritic. She also notes photosensitivity affecting her forearms and décolletage.

She denies mucosal involvement, apart from a few mouth ulcers that developed about 4-5 months ago. The ulcers have since healed and not recurred. She denies using any new medications.

Past history includes polycystic ovarian syndrome, osteoarthritis, eczema, hypertension and gastro-oesophageal reflux disease.

Her regular medications include verapamil, indapamide, potassium chloride, pantoprazole, vitamin D and paracetamol with codeine.

Figure 1
Figure 1.